ca65 Users Guide <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org"> <date>19.07.2000, 29.11.2000, 02.10.2001 <abstract> ca65 is a powerful macro assembler for the 6502, 65C02 and 65816 CPUs. It is used as a companion assembler for the cc65 crosscompiler, but it may also be used as a standalone product. </abstract>  <toc>  <sect>Overview ca65 is a replacement for the ra65 assembler that was part of the cc65 C compiler, originally developed by John R. Dunning. I had some problems with ra65 and the copyright does not permit some things which I wanted to be possible, so I decided to write a completely new assembler/linker/archiver suite for the cc65 compiler. ca65 is part of this suite. Some parts of the assembler (code generation and some routines for symbol table handling) are taken from an older crossassembler named a816 written by me a long time ago. <sect1>Design criteria Here's a list of the design criteria, that I considered important for the development: <itemize> <item> The assembler must support macros. Macros are not essential, but they make some things easier, especially when you use the assembler in the backend of a compiler. <item> The assembler must support the newer 65C02 and 65816 CPUs. I have been thinking about a 65816 backend for the C compiler, and even my old a816 assembler had support for these CPUs, so this wasn't really a problem. <item> The assembler must produce relocatable code. This is necessary for the compiler support, and it is more convenient. <item> Conditional assembly must be supported. This is a must for bigger projects written in assembler (like Elite128). <item> The assembler must support segments, and it must support more than three segments (this is the count, most other assemblers support). Having more than one code segments helps developing code for systems with a divided ROM area (like the C64). <item> The linker must be able to resolve arbitrary expressions. It should be able to get things like <tscreen><verb> .import S1, S2 .export Special Special = 2*S1 + S2/7 </verb></tscreen> right. <item> True lexical nesting for symbols. This is very convenient for larger assembly projects. <item> "Cheap" local symbols without lexical nesting for those quick, late night hacks. <item> I liked the idea of "options" as Anre Fachats .o65 format has it, so I introduced the concept into the object file format use by the new cc65 binutils. <item> The assembler will be a one pass assembler. There was no real need for this decision, but I've written several multipass assemblers, and it started to get boring. A one pass assembler needs much more elaborated data structures, and because of that it's much more fun:-) <item> Non-GPLed code that may be used in any project without restrictions or fear of "GPL infecting" other code. </itemize> <sect>Usage <sect1>Command line option overview The assembler accepts the following options: <tscreen><verb> --------------------------------------------------------------------------- Usage: ca65 [options] file Short options: -D name[=value] Define a symbol -I dir Set an include directory search path -U Mark unresolved symbols as import -V Print the assembler version -W n Set warning level n -g Add debug info to object file -h Help (this text) -i Ignore case of symbols -l Create a listing if assembly was ok -o name Name the output file -s Enable smart mode -t sys Set the target system -v Increase verbosity Long options: --auto-import Mark unresolved symbols as import --cpu type Set cpu type --debug-info Add debug info to object file --feature name Set an emulation feature --help Help (this text) --ignore-case Ignore case of symbols --include-dir dir Set an include directory search path --list-bytes n Maximum number of bytes per listing line --listing Create a listing if assembly was ok --pagelength n Set the page length for the listing --smart Enable smart mode --target sys Set the target system --verbose Increase verbosity --version Print the assembler version --------------------------------------------------------------------------- </verb></tscreen> <sect1>Command line options in detail Here is a description of all the command line options: <descrip> <label id="option--cpu"> <tag><tt>--cpu type</tt></tag> Set the default for the CPU type. The option takes a parameter, which may be one of 6502, 65SC02, 65C02, 65816 and sunplus The last one (sunplus) is not available in the freeware version, because the instruction set of the sunplus CPU is "proprietary and confidential". <label id="option--feature"> <tag><tt>--feature name</tt></tag> Enable an emulation feature. This is identical as using <tt/.FEATURE/ in the source with two exceptions: Feature names must be lower case, and each feature must be specified by using an extra <tt/--feature/ option, comma separated lists are not allowed. See the discussion of the <tt><ref id=".FEATURE" name=".FEATURE"></tt> command for a list of emulation features. <label id="option-g"> <tag><tt>-g, --debug-info</tt></tag> When this option (or the equivalent control command <tt/.DEBUGINFO/) is used, the assembler will add a section to the object file that contains all symbols (including local ones) together with the symbol values and source file positions. The linker will put these additional symbols into the VICE label file, so even local symbols can be seen in the VICE monitor. <tag><tt>-h, --help</tt></tag> Print the short option summary shown above. <tag><tt>-i, --ignore-case</tt></tag> This option makes the assembler case insensitive on identifiers and labels. This option will override the default, but may itself be overriden by the <tt><ref id=".CASE" name=".CASE"></tt> control command. <tag><tt>-l, --listing</tt></tag> Generate an assembler listing. The listing file will always have the name of the main input file with the extension replaced by ".lst". This may change in future versions. <tag><tt>--list-bytes n</tt></tag> Set the maximum number of bytes printed in the listing for one line of input. See the <tt><ref id=".LISTBYTES" name=".LISTBYTES"></tt> directive for more information. The value zero can be used to encode an unlimited number of printed bytes. <tag><tt>-o name</tt></tag> The default output name is the name of the input file with the extension replaced by ".o". If you don't like that, you may give another name with the -o option. The output file will be placed in the same directory as the source file, or, if -o is given, the full path in this name is used. <tag><tt>--pagelength n</tt></tag> sets the length of a listing page in lines. See the <tt><ref id=".PAGELENGTH" name=".PAGELENGTH"></tt> directive for more information. <tag><tt>-s, --smart-mode</tt></tag> In smart mode (enabled by -s or the <tt><ref id=".SMART" name=".SMART"></tt> pseudo instruction) the assembler will track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode and update the operand sizes accordingly. If the operand of such an instruction cannot be evaluated by the assembler (for example, because the operand is an imported symbol), a warning is issued. Beware: Since the assembler cannot trace the execution flow this may lead to false results in some cases. If in doubt, use the .ixx and .axx instructions to tell the assembler about the current settings. Smart mode is off by default. <label id="option-t"> <tag><tt>-t sys, --target sys</tt></tag> Set the target system. This will enable translation of character strings and character constants into the character set of the target platform. The default for the target system is "none", which means that no translation will take place. The assembler supports the same target systems as the compiler, see there for a list. <tag><tt>-v, --verbose</tt></tag> Increase the assembler verbosity. Usually only needed for debugging purposes. You may use this option more than one time for even more verbose output. <tag><tt>-D</tt></tag> This option allows you to define symbols on the command line. Without a value, the symbol is defined with the value zero. When giving a value, you may use the '$' prefix for hexadecimal symbols. Please note that for some operating systems, '$' has a special meaning, so you may have to quote the expression. <tag><tt>-I dir, --include-dir dir</tt></tag> Name a directory which is searched for include files. The option may be used more than once to specify more than one directory to search. The current directory is always searched first before considering any additional directores. <tag><tt>-U, --auto-import</tt></tag> Mark symbols that are not defined in the sources as imported symbols. This should be used with care since it delays error messages about typos and such until the linker is run. The compiler uses the equivalent of this switch (<tt><ref id=".AUTOIMPORT" name=".AUTOIMPORT"></tt>) to enable auto imported symbols for the runtime library. However, the compiler is supposed to generate code that runs through the assembler without problems, something which is not always true for assembler programmers. <tag><tt>-V, --version</tt></tag> Print the version number of the assembler. If you send any suggestions or bugfixes, please include the version number. <label id="option-W"> <tag><tt>-Wn</tt></tag> Set the warning level for the assembler. Using -W2 the assembler will even warn about such things like unused imported symbols. The default warning level is 1, and it would probably be silly to set it to something lower. </descrip> <sect>Input format <sect1>Assembler syntax The assembler accepts the standard 6502/65816 assembler syntax. One line may contain a label (which is identified by a colon), and, in addition to the label, an assembler mnemonic, a macro, or a control command (see section <ref id="control-commands" name="Control Commands"> for supported control commands). Alternatively, the line may contain a symbol definition using the '=' token. Everything after a semicolon is handled as a comment (that is, it is ignored). Here are some examples for valid input lines: <tscreen><verb> Label: ; A label and a comment lda #$20 ; A 6502 instruction plus comment L1: ldx #$20 ; Same with label L2: .byte "Hello world" ; Label plus control command mymac $20 ; Macro expansion MySym = 3*L1 ; Symbol definition MaSym = Label ; Another symbol </verb></tscreen> The assembler accepts <itemize> <item>all valid 6502 mnemonics when in 6502 mode (the default or after the <tt><ref id=".P02" name=".P02"></tt> command was given). <item>all valid 6502 mnemonics plus a set of illegal instructions when in <ref id="6502X-mode" name="6502X mode">. <item>all valid 65SC02 mnemonics when in 65SC02 mode (after the <tt><ref id=".PSC02" name=".PSC02"></tt> command was given). <item>all valid 65C02 mnemonics when in 65C02 mode (after the <tt><ref id=".PC02" name=".PC02"></tt> command was given). <item>all valid 65618 mnemonics when in 65816 mode (after the <tt><ref id=".P816" name=".P816"></tt> command was given). <item>all valid SunPlus mnemonics when in SunPlus mode (after the <tt><ref id=".SUNPLUS" name=".SUNPLUS"></tt> command was given). </itemize> <sect1>65816 mode In 65816 mode several aliases are accepted in addition to the official mnemonics: <tscreen><verb> BGE is an alias for BCS BLT is an alias for BCC CPA is an alias for CMP DEA is an alias for DEC A INA is an alias for INC A SWA is an alias for XBA TAD is an alias for TCD TAS is an alias for TCS TDA is an alias for TDC TSA is an alias for TSC </verb></tscreen> <sect1>6502X mode<label id="6502X-mode"> 6502X mode is an extension to the normal 6502 mode. In this mode, several mnemomics for illegal instructions of the NMOS 6502 CPUs are accepted. Since these instructions are illegal, there are no official mnemonics for them. The unofficial ones are taken from <htmlurl url="http://oxyron.net/graham/opcodes02.html" name="http://oxyron.net/graham/opcodes02.html">. Please note that only the ones marked as "stable" are supported. The following table uses information from the mentioned web page, for more information, see there. <itemize> <item><tt>ALR: A:=(A and #{imm})*2;</tt> <item><tt>ANC: A:=A and #{imm};</tt> Generates opcode $0B. <item><tt>ARR: A:=(A and #{imm})/2;</tt> <item><tt>AXS: X:=A and X-#{imm};</tt> <item><tt>DCP: {adr}:={adr}-1; A-{adr};</tt> <item><tt>ISC: {adr}:={adr}+1; A:=A-{adr};</tt> <item><tt>LAS: A,X,S:={adr} and S;</tt> <item><tt>LAX: A,X:={adr};</tt> <item><tt>RLA: {adr}:={adr}rol; A:=A and {adr};</tt> <item><tt>RRA: {adr}:={adr}ror; A:=A adc {adr};</tt> <item><tt>SAX: {adr}:=A and X;</tt> <item><tt>SLO: {adr}:={adr}*2; A:=A or {adr};</tt> <item><tt>SRE: {adr}:={adr}/2; A:=A xor {adr};</tt> </itemize> <sect1>Number format For literal values, the assembler accepts the widely used number formats: A preceeding '$' denotes a hex value, a preceeding '%' denotes a binary value, and a bare number is interpeted as a decimal. There are currently no octal values and no floats. <sect1>Conditional assembly Please note that when using the conditional directives (<tt/.IF/ and friends), the input must consist of valid assembler tokens, even in <tt/.IF/ branches that are not assembled. The reason for this behaviour is that the assembler must still be able to detect the ending tokens (like <tt/.ENDIF/), so conversion of the input stream into tokens still takes place. As a consequence conditional assembly directives may <bf/not/ be used to prevent normal text (used as a comment or similar) from being assembled. <sect>Expressions <sect1>Expression evaluation All expressions are evaluated with (at least) 32 bit precision. An expression may contain constant values and any combination of internal and external symbols. Expressions that cannot be evaluated at assembly time are stored inside the object file for evaluation by the linker. Expressions referencing imported symbols must always be evaluated by the linker. <sect1>Size of an expression result Sometimes, the assembler must know about the size of the value that is the result of an expression. This is usually the case, if a decision has to be made, to generate a zero page or an absolute memory references. In this case, the assembler has to make some assumptions about the result of an expression: <itemize> <item> If the result of an expression is constant, the actual value is checked to see if it's a byte sized expression or not. <item> If the expression is explicitly casted to a byte sized expression by one of the '>', '<' or '^' operators, it is a byte expression. <item> If this is not the case, and the expression contains a symbol, explicitly declared as zero page symbol (by one of the .importzp or .exportzp instructions), then the whole expression is assumed to be byte sized. <item> If the expression contains symbols that are not defined, and these symbols are local symbols, the enclosing scopes are searched for a symbol with the same name. If one exists and this symbol is defined, it's attributes are used to determine the result size. <item> In all other cases the expression is assumed to be word sized. </itemize> Note: If the assembler is not able to evaluate the expression at assembly time, the linker will evaluate it and check for range errors as soon as the result is known. <sect1>Boolean expressions In the context of a boolean expression, any non zero value is evaluated as true, any other value to false. The result of a boolean expression is 1 if it's true, and zero if it's false. There are boolean operators with extrem low precedence with version 2.x (where x > 0). The <tt/.AND/ and <tt/.OR/ operators are shortcut operators. That is, if the result of the expression is already known, after evaluating the left hand side, the right hand side is not evaluated. <sect1>Constant expressions Sometimes an expression must evaluate to a constant without looking at any further input. One such example is the <tt/<ref id=".IF" name=".IF">/ command that decides if parts of the code are assembled or not. An expression used in the <tt/.IF/ command cannot reference a symbol defined later, because the decision about the <tt/.IF/ must be made at the point when it is read. If the expression used in such a context contains only constant numerical values, there is no problem. When unresolvable symbols are involved it may get harder for the assembler to determine if the expression is actually constant, and it is even possible to create expressions that aren't recognized as constant. Simplifying the expressions will often help. In cases where the result of the expression is not needed immediately, the assembler will delay evaluation until all input is read, at which point all symbols are known. So using arbitrary complex constant expressions is no problem in most cases. <sect1>Available operators<label id="operators"> Available operators sorted by precedence: <tscreen><verb> Op Description Precedence ------------------------------------------------------------------- Builtin string functions 0 Builtin pseudo variables 1 Builtin pseudo functions 1 + Unary plus 1 - Unary minus 1 ~ Unary bitwise not 1 .BITNOT Unary bitwise not 1 < Low byte operator 1 > High byte operator 1 ^ Bank byte operator 1 * Multiplication 2 / Division 2 .MOD Modulo operation 2 & Bitwise and 2 .BITAND Bitwise and 2 ^ Bitwise xor 2 .BITXOR Bitwise xor 2 << Shift left operator 2 .SHL Shift left operator 2 >> Shift right operator .SHR Shift right operator 2 + Binary plus 3 - Binary minus 3 | Binary or 3 .BITOR Binary or 3 = Compare operation (equal) 4 <> Compare operation (not equal) 4 < Compare operation (less) 4 > Compare operation (greater) 4 <= Compare operation (less or equal) 4 >= Compare operation (greater or equal) 4 && Boolean and 5 .AND Boolean and 5 .XOR Boolean xor 5 || Boolean or 6 .OR Boolean or 6 ! Boolean not 7 .NOT Boolean not 7 </verb></tscreen> To force a specific order of evaluation, braces may be used as usual. <sect>Symbols and labels The assembler allows you to use symbols instead of naked values to make the source more readable. There are a lot of different ways to define and use symbols and labels, giving a lot of flexibility. <sect1>Numeric constants Numeric constants are defined using the equal sign or the label assignment operator. After doing <tscreen><verb> two = 2 </verb></tscreen> may use the symbol "two" in every place where a number is expected, and it is evaluated to the value 2 in this context. The label assignment operator causes the same, but causes the symbol to be marked as a label, which may cause a different handling in the debugger: <tscreen><verb> io := $d000 </verb></tscreen> The right side can of course be an expression: <tscreen><verb> four = two * two </verb></tscreen> <sect1>Standard labels A label is defined by writing the name of the label at the start of the line (before any instruction mnemonic, macro or pseudo directive), followed by a colon. This will declare a symbol with the given name and the value of the current program counter. <sect1>Local labels and symbols Using the <tt><ref id=".PROC" name=".PROC"></tt> directive, it is possible to create regions of code where the names of labels and symbols are local to this region. They are not known outside of this region and cannot be accessed from there. Such regions may be nested like PROCEDUREs in Pascal. See the description of the <tt><ref id=".PROC" name=".PROC"></tt> directive for more information. <sect1>Cheap local labels Cheap local labels are defined like standard labels, but the name of the label must begin with a special symbol (usually '@', but this can be changed by the <tt><ref id=".LOCALCHAR" name=".LOCALCHAR"></tt> directive). Cheap local labels are visible only between two non cheap labels. As soon as a standard symbol is encountered (this may also be a local symbol if inside a region defined with the <tt><ref id=".PROC" name=".PROC"></tt> directive), the cheap local symbol goes out of scope. You may use cheap local labels as an easy way to reuse common label names like "Loop". Here is an example: <tscreen><verb> Clear: lda #$00 ; Global label ldy #$20 @Loop: sta Mem,y ; Local label dey bne @Loop ; Ok rts Sub: ... ; New global label bne @Loop ; ERROR: Unknown identifier! </verb></tscreen> <sect1>Unnamed labels If you really want to write messy code, there are also unnamed labels. These labels do not have a name (you guessed that already, didn't you?). A colon is used to mark the absence of the name. Unnamed labels may be accessed by using the colon plus several minus or plus characters as a label designator. Using the '-' characters will create a back reference (use the n'th label backwards), using '+' will create a forward reference (use the n'th label in forward direction). An example will help to understand this: <tscreen><verb> : lda (ptr1),y ; #1 cmp (ptr2),y bne :+ ; -> #2 tax beq :+++ ; -> #4 iny bne :- ; -> #1 inc ptr1+1 inc ptr2+1 bne :- ; -> #1 : bcs :+ ; #2 -> #3 ldx #$FF rts : ldx #$01 ; #3 : rts ; #4 </verb></tscreen> As you can see from the example, unnamed labels will make even short sections of code hard to understand, because you have to count labels to find branch targets (this is the reason why I for my part do prefer the "cheap" local labels). Nevertheless, unnamed labels are convenient in some situations, so it's your decision. <sect1>Using macros to define labels and constants While there are drawbacks with this approach, it may be handy in some situations. Using <tt><ref id=".DEFINE" name=".DEFINE"></tt>, it is possible to define symbols or constants that may be used elsewhere. Since the macro facility works on a very low level, there is no scoping. On the other side, you may also define string constants this way (this is not possible with the other symbol types). Example: <tscreen><verb> .DEFINE two 2 .DEFINE version "SOS V2.3" four = two * two ; Ok .byte version ; Ok .PROC ; Start local scope two = 3 ; Will give "2 = 3" - invalid! .ENDPROC </verb></tscreen> <sect1>Symbols and <tt>.DEBUGINFO</tt> If <tt><ref id=".DEBUGINFO" name=".DEBUGINFO"></tt> is enabled (or <ref id="option-g" name="-g"> is given on the command line), global, local and cheap local labels are written to the object file and will be available in the symbol file via the linker. Unnamed labels are not written to the object file, because they don't have a name which would allow to access them. <sect>Scopes<label id="scopes"> ca65 implements several sorts of scopes for symbols. <sect1>Global scope All (non cheap local) symbols that are declared outside of any nested scopes are in global scope. <sect1>A special scope: cheap locals A special scope is the scope for cheap local symbols. It lasts from one non local symbol to the next one, without any provisions made by the programmer. All other scopes differ in usage but use the same concept internally. <sect1>Generic nested scopes A nested scoped for generic use is started with <tt/<ref id=".SCOPE" name=".SCOPE">/ and closed with <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/. The scope can have a name, in which case it is accessible from the outside by using <ref id="scopesyntax" name="explicit scopes">. If the scope does not have a name, all symbols created within the scope are local to the scope, and aren't accessible from the outside. A nested scope can access symbols from the local or from enclosing scopes by name without using explicit scope names. In some cases there may be ambiguities, for example if there is a reference to a local symbol that is not yet defined, but a symbol with the same name exists in outer scopes: <tscreen><verb> .scope outer foo = 2 .scope inner lda #foo foo = 3 .endscope .endscope </verb></tscreen> In the example above, the <tt/lda/ instruction will load the value 3 into the accumulator, because <tt/foo/ is redefined in the scope. However: <tscreen><verb> .scope outer foo = $1234 .scope inner lda foo,x foo = $12 .endscope .endscope </verb></tscreen> Here, <tt/lda/ will still load from <tt/$12,x/, but since it is unknown to the assembler that <tt/foo/ is a zeropage symbol when translating the instruction, absolute mode is used instead. In fact, the assembler will not use absolute mode by default, but it will search through the enclosing scopes for a symbol with the given name. If one is found, the address size of this symbol is used. This may lead to errors: <tscreen><verb> .scope outer foo = $12 .scope inner lda foo,x foo = $1234 .endscope .endscope </verb></tscreen> In this case, when the assembler sees the symbol <tt/foo/ in the <tt/lda/ instruction, it will search for an already defined symbol <tt/foo/. It will find <tt/foo/ in scope <tt/outer/, and a close look reveals that it is a zeropage symbol. So the assembler will use zeropage addressing mode. If <tt/foo/ is redefined later in scope <tt/inner/, the assembler tries to change the address in the <tt/lda/ instruction already translated, but since the new value needs absolute addressing mode, this fails, and an error message "Range error" is output. Of course the most simple solution for the problem is to move the definition of <tt/foo/ in scope <tt/inner/ upwards, so it preceeds its use. There may be rare cases when this cannot be done. In these cases, you can use one of the address size override operators: <tscreen><verb> .scope outer foo = $12 .scope inner lda a:foo,x foo = $1234 .endscope .endscope </verb></tscreen> This will cause the <tt/lda/ instruction to be translated using absolute addressing mode, which means changing the symbol reference later does not cause any errors. <sect1>Nested procedures A nested procedure is created by use of <tt/<ref id=".PROC" name=".PROC">/. It differs from a <tt/<ref id=".SCOPE" name=".SCOPE">/ in that it must have a name, and a it will introduce a symbol with this name in the enclosing scope. So <tscreen><verb> .proc foo ... .endscope </verb></tscreen> is actually the same as <tscreen><verb> foo: .scope foo ... .endscope </verb></tscreen> This is the reason why a procedure must have a name. If you want a scope without a name, use <tt/<ref id=".SCOPE" name=".SCOPE">/. <bf/Note:/ As you can see from the example above, scopes and symbols live in different namespaces. There can be a symbol named <tt/foo/ and a scope named <tt/foo/ without any conflicts (but see the section titled <ref id="scopesearch" name=""Scope search order"">). <sect1>Structs, unions and enums Structs, unions and enums are explained in a <ref id="structs" name="separate section">, I do only cover them here, because if they are declared with a name, they open a nested scope, similar to <tt/<ref id=".SCOPE" name=".SCOPE">/. However, when no name is specified, the behaviour is different: In this case, no new scope will be opened, symbols declared within a struct, union, or enum declaration will then be added to the enclosing scope instead. <sect1>Explicit scope specification<label id="scopesyntax"> Accessing symbols from other scopes is possible by using an explicit scope specification, provided that the scope where the symbol lives in has a name. The namespace token (<tt/::/) is used to access other scopes: <tscreen><verb> .scope foo bar: .word 0 .endscope ... lda foo::bar ; Access foo in scope bar </verb></tscreen> The only way to deny access to a scope from the outside is to declare a scope without a name (using the <tt/<ref id=".SCOPE" name=".SCOPE">/ command). A special syntax is used to specify the global scope: If a symbol or scope is preceeded by the namespace token, the global scope is searched: <tscreen><verb> bar = 3 .scope foo bar = 2 lda #::bar ; Access the global bar (which is 3) .endscope </verb></tscreen> <sect1>Scope search order<label id="scopesearch"> The assembler searches for a scope in a similar way as for a symbol. First, it looks in the current scope, and then it walks up the enclosing scopes until the scope is found. However, one important thing to note when using explicit scope syntax is, that a symbol may be accessed before it is defined, but a scope may <bf/not/ be used without a preceeding definition. This means that in the following example: <tscreen><verb> .scope foo bar = 3 .endscope .scope outer lda #foo::bar ; Will load 3, not 2! .scope foo bar = 2 .endscope .endscope </verb></tscreen> the reference to the scope <tt/foo/ will use the global scope, and not the local one, because the local one is not visible at the point where it is referenced. Things get more complex if a complete chain of scopes is specified: <tscreen><verb> .scope foo .scope outer .scope inner bar = 1 .endscope .endscope .scope another .scope nested lda #outer::inner::bar ; 1 .endscope .endscope .endscope .scope outer .scope inner bar = 2 .endscope .endscope </verb></tscreen> When <tt/outer::inner::bar/ is referenced in the <tt/lda/ instruction, the assembler will first search in the local scope for a scope named <tt/outer/. Since none is found, the enclosing scope (<tt/another/) is checked. There is still no scope named <tt/outer/, so scope <tt/foo/ is checked, and finally scope <tt/outer/ is found. Within this scope, <tt/inner/ is searched, and in this scope, the assembler looks for a symbol named <tt/bar/. Please note that once the anchor scope is found, all following scopes (<tt/inner/ in this case) are expected to be found exactly in this scope. The assembler will search the scope tree only for the first scope (if it is not anchored in the root scope). Starting from there on, there is no flexibility, so if the scope named <tt/outer/ found by the assembler does not contain a scope named <tt/inner/, this would be an error, even if such a pair does exist (one level up in global scope). Ambiguities that may be introduced by this search algorithm may be removed by anchoring the scope specification in the global scope. In the example above, if you want to access the "other" symbol <tt/bar/, you would have to write: <tscreen><verb> .scope foo .scope outer .scope inner bar = 1 .endscope .endscope .scope another .scope nested lda #::outer::inner::bar ; 2 .endscope .endscope .endscope .scope outer .scope inner bar = 2 .endscope .endscope </verb></tscreen> <sect>Address sizes and memory models<label id="address-sizes"> <sect1>Address sizes ca65 assigns each segment and each symbol an address size. This is true, even if the symbol is not used as an address. You may also think of a value range of the symbol instead of an address size. Possible address sizes are: <itemize> <item>Zeropage or direct (8 bits) <item>Absolute (16 bits) <item>Far (24 bits) <item>Long (32 bits) </itemize> Since the assembler uses default address sizes for the segments and symbols, it is usually not necessary to override the default behaviour. In cases, where it is necessary, the following keywords may be used to specify address sizes: <itemize> <item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits). <item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits). <item>FAR for far addressing (24 bits). <item>LONG or DWORD for long addressing (32 bits). </itemize> <sect1>Address sizes of segments The assembler assigns an address size to each segment. Since the representation of a label within this segment is "segment start + offset", labels will inherit the address size of the segment they are declared in. The address size of a segment may be changed, by using an optional address size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for an explanation on how this is done. <sect1>Address sizes of symbols <sect1>Memory models The default address size of a segment depends on the memory model used. Since labels inherit the address size from the segment they are declared in, changing the memory model is an easy way to change the address size of many symbols at once. <sect>Pseudo variables<label id="pseudo-variables"> Pseudo variables are readable in all cases, and in some special cases also writable. <sect1><tt>*</tt> Reading this pseudo variable will return the program counter at the start of the current input line. Assignment to this variable is possible when <tt/<ref id=".FEATURE" name=".FEATURE pc_assignment">/ is used. Note: You should not use assignments to <tt/*/, use <tt/<ref id=".ORG" name=".ORG">/ instead. <sect1><tt>.CPU</tt><label id=".CPU"> Reading this pseudo variable will give a constant integer value that tells which CPU is currently enabled. It can also tell which instruction set the CPU is able to translate. The value read from the pseudo variable should be further examined by using one of the constants defined by the "cpu" macro package (see <tt/<ref id=".MACPACK" name=".MACPACK">/). It may be used to replace the .IFPxx pseudo instructions or to construct even more complex expressions. Example: <tscreen><verb> .macpack cpu .if (.cpu .bitand CPU_ISET_65816) phx phy .else txa pha tya pha .endif </verb></tscreen> <sect1><tt>.PARAMCOUNT</tt><label id=".PARAMCOUNT"> This builtin pseudo variable is only available in macros. It is replaced by the actual number of parameters that were given in the macro invocation. Example: <tscreen><verb> .macro foo arg1, arg2, arg3 .if .paramcount <> 3 .error "Too few parameters for macro foo" .endif ... .endmacro </verb></tscreen> See section <ref id="macros" name="Macros">. <sect1><tt>.TIME</tt><label id=".TIME"> Reading this pseudo variable will give a constant integer value that represents the current time in POSIX standard (as seconds since the Epoch). It may be used to encode the time of translation somewhere in the created code. Example: <tscreen><verb> .dword .time ; Place time here </verb></tscreen> <sect1><tt>.VERSION</tt><label id=".VERSION"> Reading this pseudo variable will give the assembler version according to the following formula: VER_MAJOR*$100 + VER_MINOR*$10 + VER_PATCH It may be used to encode the assembler version or check the assembler for special features not available with older versions. Example: Version 2.11.1 of the assembler will return $2B1 as numerical constant when reading the pseudo variable <tt/.VERSION/. <sect>Pseudo functions<label id="pseudo-functions"> Pseudo functions expect their arguments in parenthesis, and they have a result, either a string or an expression. <sect1><tt>.BANKBYTE</tt><label id=".BANKBYTE"> The function returns the bank byte (that is, bits 16-23) of its argument. It works identical to the '^' operator. See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>, <tt><ref id=".LOBYTE" name=".LOBYTE"></tt> <sect1><tt>.BLANK</tt><label id=".BLANK"> Builtin function. The function evaluates its argument in braces and yields "false" if the argument is non blank (there is an argument), and "true" if there is no argument. The token list that makes up the function argument may optionally be enclosed in curly braces. This allows the inclusion of tokens that would otherwise terminate the list (the closing right parenthesis). The curly braces are not considered part of the list, a list just consisting of curly braces is considered to be empty. As an example, the <tt/.IFBLANK/ statement may be replaced by <tscreen><verb> .if .blank({arg}) </verb></tscreen> <sect1><tt>.CONCAT</tt><label id=".CONCAT"> Builtin string function. The function allows to concatenate a list of string constants separated by commas. The result is a string constant that is the concatentation of all arguments. This function is most useful in macros and when used together with the <tt/.STRING/ builtin function. The function may be used in any case where a string constant is expected. Example: <tscreen><verb> .include .concat ("myheader", ".", "inc") </verb></tscreen> This is the same as the command <tscreen><verb> .include "myheader.inc" </verb></tscreen> <sect1><tt>.CONST</tt><label id=".CONST"> Builtin function. The function evaluates its argument in braces and yields "true" if the argument is a constant expression (that is, an expression that yields a constant value at assembly time) and "false" otherwise. As an example, the .IFCONST statement may be replaced by <tscreen><verb> .if .const(a + 3) </verb></tscreen> <sect1><tt>.HIBYTE</tt><label id=".HIBYTE"> The function returns the high byte (that is, bits 8-15) of its argument. It works identical to the '>' operator. See: <tt><ref id=".LOBYTE" name=".LOBYTE"></tt>, <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt> <sect1><tt>.HIWORD</tt><label id=".HIWORD"> The function returns the high word (that is, bits 16-31) of its argument. See: <tt><ref id=".LOWORD" name=".LOWORD"></tt> <sect1><tt>.LEFT</tt><label id=".LEFT"> Builtin function. Extracts the left part of a given token list. Syntax: <tscreen><verb> .LEFT (<int expr>, <token list>) </verb></tscreen> The first integer expression gives the number of tokens to extract from the token list. The second argument is the token list itself. The token list may optionally be enclosed into curly braces. This allows the inclusion of tokens that would otherwise terminate the list (the closing right paren in the given case). Example: To check in a macro if the given argument has a '#' as first token (immidiate addressing mode), use something like this: <tscreen><verb> .macro ldax arg ... .if (.match (.left (1, {arg}), #)) ; ldax called with immidiate operand ... .endif ... .endmacro </verb></tscreen> See also the <tt><ref id=".MID" name=".MID"></tt> and <tt><ref id=".RIGHT" name=".RIGHT"></tt> builtin functions. <sect1><tt>.LOBYTE</tt><label id=".LOBYTE"> The function returns the low byte (that is, bits 0-7) of its argument. It works identical to the '<' operator. See: <tt><ref id=".HIBYTE" name=".HIBYTE"></tt>, <tt><ref id=".BANKBYTE" name=".BANKBYTE"></tt> <sect1><tt>.LOWORD</tt><label id=".LOWORD"> The function returns the low word (that is, bits 0-15) of its argument. See: <tt><ref id=".HIWORD" name=".HIWORD"></tt> <sect1><tt>.MATCH</tt><label id=".MATCH"> Builtin function. Matches two token lists against each other. This is most useful within macros, since macros are not stored as strings, but as lists of tokens. The syntax is <tscreen><verb> .MATCH(<token list #1>, <token list #2>) </verb></tscreen> Both token list may contain arbitrary tokens with the exception of the terminator token (comma resp. right parenthesis) and <itemize> <item>end-of-line <item>end-of-file </itemize> The token lists may optionally be enclosed into curly braces. This allows the inclusion of tokens that would otherwise terminate the list (the closing right paren in the given case). Often a macro parameter is used for any of the token lists. Please note that the function does only compare tokens, not token attributes. So any number is equal to any other number, regardless of the actual value. The same is true for strings. If you need to compare tokens <em/and/ token attributes, use the <tt><ref id=".XMATCH" name=".XMATCH"></tt> function. Example: Assume the macro <tt/ASR/, that will shift right the accumulator by one, while honoring the sign bit. The builtin processor instructions will allow an optional "A" for accu addressing for instructions like <tt/ROL/ and <tt/ROR/. We will use the <tt><ref id=".MATCH" name=".MATCH"></tt> function to check for this and print and error for invalid calls. <tscreen><verb> .macro asr arg .if (.not .blank(arg)) .and (.not .match ({arg}, a)) .error "Syntax error" .endif cmp #$80 ; Bit 7 into carry lsr a ; Shift carry into bit 7 .endmacro </verb></tscreen> The macro will only accept no arguments, or one argument that must be the reserved keyword "A". See: <tt><ref id=".XMATCH" name=".XMATCH"></tt> <sect1><tt>.MID</tt><label id=".MID"> Builtin function. Takes a starting index, a count and a token list as arguments. Will return part of the token list. Syntax: <tscreen><verb> .MID (<int expr>, <int expr>, <token list>) </verb></tscreen> The first integer expression gives the starting token in the list (the first token has index 0). The second integer expression gives the number of tokens to extract from the token list. The third argument is the token list itself. The token list may optionally be enclosed into curly braces. This allows the inclusion of tokens that would otherwise terminate the list (the closing right paren in the given case). Example: To check in a macro if the given argument has a '<tt/#/' as first token (immidiate addressing mode), use something like this: <tscreen><verb> .macro ldax arg ... .if (.match (.mid (0, 1, {arg}), #)) ; ldax called with immidiate operand ... .endif ... .endmacro </verb></tscreen> See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".RIGHT" name=".RIGHT"></tt> builtin functions. <sect1><tt>.REF, .REFERENCED</tt><label id=".REFERENCED"> Builtin function. The function expects an identifier as argument in braces. The argument is evaluated, and the function yields "true" if the identifier is a symbol that has already been referenced somewhere in the source file up to the current position. Otherwise the function yields false. As an example, the <tt><ref id=".IFREF" name=".IFREF"></tt> statement may be replaced by <tscreen><verb> .if .referenced(a) </verb></tscreen> See: <tt><ref id=".DEFINED" name=".DEFINED"></tt> <sect1><tt>.RIGHT</tt><label id=".RIGHT"> Builtin function. Extracts the right part of a given token list. Syntax: <tscreen><verb> .RIGHT (<int expr>, <token list>) </verb></tscreen> The first integer expression gives the number of tokens to extract from the token list. The second argument is the token list itself. The token list may optionally be enclosed into curly braces. This allows the inclusion of tokens that would otherwise terminate the list (the closing right paren in the given case). See also the <tt><ref id=".LEFT" name=".LEFT"></tt> and <tt><ref id=".MID" name=".MID"></tt> builtin functions. <sect1><tt>.SIZEOF</tt><label id=".SIZEOF"> <tt/.SIZEOF/ is a pseudo function that returns the size of its argument. The argument can be a struct/union, a struct member, a procedure, or a label. In case of a procedure or label, its size is defined by the amount of data placed in the segment where the label is relative to. If a line of code switches segments (for example in a macro) data placed in other segments does not count for the size. Please note that a symbol or scope must exist, before it is used together with <tt/.SIZEOF/ (this may get relaxed later, but will always be true for scopes). A scope has preference over a symbol with the same name, so if the last part of a name represents both, a scope and a symbol, the scope is choosen over the symbol. After the following code: <tscreen><verb> .struct Point ; Struct size = 4 xcoord .word xcoord .word .endstruct P: .tag Point ; Declare a point @P: .tag Point ; Declare another point .code .proc Code nop .proc Inner nop .endproc nop .endproc .proc Data .data ; Segment switch!!! .res 4 .endproc </verb></tscreen> <descrip> <tag><tt/.sizeof(Point)/</tag> will have the value 4, because this is the size of struct <tt/Point/. <tag><tt/.sizeof(Point::xcoord)/</tag> will have the value 2, because this is the size of the member <tt/xcoord/ in struct <tt/Point/. <tag><tt/.sizeof(P)/</tag> will have the value 4, this is the size of the data declared on the same source line as the label <tt/P/, which is in the same segment that <tt/P/ is relative to. <tag><tt/.sizeof(@P)/</tag> will have the value 4, see above. The example demonstrates that <tt/.SIZEOF/ does also work for cheap local symbols. <tag><tt/.sizeof(Code)/</tag> will have the value 3, since this is amount of data emitted into the code segment, the segment that was active when <tt/Code/ was entered. Note that this value includes the amount of data emitted in child scopes (in this case <tt/Code::Inner/). <tag><tt/.sizeof(Code::Inner)/</tag> will have the value 1 as expected. <tag><tt/.sizeof(Data)/</tag> will have the value 0. Data is emitted within the scope <tt/Data/, but since the segment is switched after entry, this data is emitted into another segment. </descrip> <sect1><tt>.STRAT</tt><label id=".STRAT"> Builtin function. The function accepts a string and an index as arguments and returns the value of the character at the given position as an integer value. The index is zero based. Example: <tscreen><verb> .macro M Arg ; Check if the argument string starts with '#' .if (.strat (Arg, 0) = '#') ... .endif .endmacro </verb></tscreen> <sect1><tt>.STRING</tt><label id=".STRING"> Builtin function. The function accepts an argument in braces and converts this argument into a string constant. The argument may be an identifier, or a constant numeric value. Since you can use a string in the first place, the use of the function may not be obvious. However, it is useful in macros, or more complex setups. Example: <tscreen><verb> ; Emulate other assemblers: .macro section name .segment .string(name) .endmacro </verb></tscreen> <sect1><tt>.STRLEN</tt><label id=".STRLEN"> Builtin function. The function accepts a string argument in braces and eveluates to the length of the string. Example: The following macro encodes a string as a pascal style string with a leading length byte. <tscreen><verb> .macro PString Arg .byte .strlen(Arg), Arg .endmacro </verb></tscreen> <sect1><tt>.TCOUNT</tt><label id=".TCOUNT"> Builtin function. The function accepts a token list in braces. The function result is the number of tokens given as argument. The token list may optionally be enclosed into curly braces which are not considered part of the list and not counted. Enclosement in curly braces allows the inclusion of tokens that would otherwise terminate the list (the closing right paren in the given case). Example: The <tt/ldax/ macro accepts the '#' token to denote immidiate addressing (as with the normal 6502 instructions). To translate it into two separate 8 bit load instructions, the '#' token has to get stripped from the argument: <tscreen><verb> .macro ldax arg .if (.match (.mid (0, 1, {arg}), #)) ; ldax called with immidiate operand lda #<(.right (.tcount ({arg})-1, {arg})) ldx #>(.right (.tcount ({arg})-1, {arg})) .else ... .endif .endmacro </verb></tscreen> <sect1><tt>.XMATCH</tt><label id=".XMATCH"> Builtin function. Matches two token lists against each other. This is most useful within macros, since macros are not stored as strings, but as lists of tokens. The syntax is <tscreen><verb> .XMATCH(<token list #1>, <token list #2>) </verb></tscreen> Both token list may contain arbitrary tokens with the exception of the terminator token (comma resp. right parenthesis) and <itemize> <item>end-of-line <item>end-of-file </itemize> The token lists may optionally be enclosed into curly braces. This allows the inclusion of tokens that would otherwise terminate the list (the closing right paren in the given case). Often a macro parameter is used for any of the token lists. The function compares tokens <em/and/ token values. If you need a function that just compares the type of tokens, have a look at the <tt><ref id=".MATCH" name=".MATCH"></tt> function. See: <tt><ref id=".MATCH" name=".MATCH"></tt> <sect>Control commands<label id="control-commands"> Here's a list of all control commands and a description, what they do: <sect1><tt>.A16</tt><label id=".A16"> Valid only in 65816 mode. Switch the accumulator to 16 bit. Note: This command will not emit any code, it will tell the assembler to create 16 bit operands for immediate accumulator adressing mode. See also: <tt><ref id=".SMART" name=".SMART"></tt> <sect1><tt>.A8</tt><label id=".A8"> Valid only in 65816 mode. Switch the accumulator to 8 bit. Note: This command will not emit any code, it will tell the assembler to create 8 bit operands for immediate accu adressing mode. See also: <tt><ref id=".SMART" name=".SMART"></tt> <sect1><tt>.ADDR</tt><label id=".ADDR"> Define word sized data. In 6502 mode, this is an alias for <tt/.WORD/ and may be used for better readability if the data words are address values. In 65816 mode, the address is forced to be 16 bit wide to fit into the current segment. See also <tt><ref id=".FARADDR" name=".FARADDR"></tt>. The command must be followed by a sequence of (not necessarily constant) expressions. Example: <tscreen><verb> .addr $0D00, $AF13, _Clear </verb></tscreen> See: <tt><ref id=".FARADDR" name=".FARADDR"></tt>, <tt><ref id=".WORD" name=".WORD"></tt> <sect1><tt>.ALIGN</tt><label id=".ALIGN"> Align data to a given boundary. The command expects a constant integer argument that must be a power of two, plus an optional second argument in byte range. If there is a second argument, it is used as fill value, otherwise the value defined in the linker configuration file is used (the default for this value is zero). Since alignment depends on the base address of the module, you must give the same (or a greater) alignment for the segment when linking. The linker will give you a warning, if you don't do that. Example: <tscreen><verb> .align 256 </verb></tscreen> <sect1><tt>.ASCIIZ</tt><label id=".ASCIIZ"> Define a string with a trailing zero. Example: <tscreen><verb> Msg: .asciiz "Hello world" </verb></tscreen> This will put the string "Hello world" followed by a binary zero into the current segment. There may be more strings separated by commas, but the binary zero is only appended once (after the last one). <sect1><tt>.ASSERT</tt><label id=".ASSERT"> Add an assertion. The command is followed by an expression, an action specifier and a message that is output in case the assertion fails. The action specifier may be one of <tt/warning/ or <tt/error/. The assertion is passed to the linker and will be evaluated when segment placement has been done. Example: <tscreen><verb> .assert * = $8000, error, "Code not at $8000" </verb></tscreen> The example assertion will check that the current location is at $8000, when the output file is written, and abort with an error if this is not the case. More complex expressions are possible. The action specifier <tt/warning/ outputs a warning, while the <tt/error/ specifier outputs an error message. In the latter case, generation if the output file is suppressed. <sect1><tt>.AUTOIMPORT</tt><label id=".AUTOIMPORT"> Is followed by a plus or a minus character. When switched on (using a +), undefined symbols are automatically marked as import instead of giving errors. When switched off (which is the default so this does not make much sense), this does not happen and an error message is displayed. The state of the autoimport flag is evaluated when the complete source was translated, before outputing actual code, so it is <em/not/ possible to switch this feature on or off for separate sections of code. The last setting is used for all symbols. You should probably not use this switch because it delays error messages about undefined symbols until the link stage. The cc65 compiler (which is supposed to produce correct assembler code in all circumstances, something which is not true for most assembler programmers) will insert this command to avoid importing each and every routine from the runtime library. Example: <tscreen><verb> .autoimport + ; Switch on auto import </verb></tscreen> <sect1><tt>.BSS</tt><label id=".BSS"> Switch to the BSS segment. The name of the BSS segment is always "BSS", so this is a shortcut for <tscreen><verb> .segment "BSS" </verb></tscreen> See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command. <sect1><tt>.BYT, .BYTE</tt><label id=".BYTE"> Define byte sized data. Must be followed by a sequence of (byte ranged) expressions or strings. Example: <tscreen><verb> .byte "Hello " .byt "world", $0D, $00 </verb></tscreen> <sect1><tt>.CASE</tt><label id=".CASE"> Switch on or off case sensitivity on identifiers. The default is off (that is, identifiers are case sensitive), but may be changed by the -i switch on the command line. The command must be followed by a '+' or '-' character to switch the option on or off respectively. Example: <tscreen><verb> .case - ; Identifiers are not case sensitive </verb></tscreen> <sect1><tt>.CHARMAP</tt><label id=".CHARMAP"> Apply a custom mapping for characters. The command is followed by two numbers in the range 1..255. The first one is the index of the source character, the second one is the mapping. The mapping applies to all character and string constants when they generate output, and overrides a mapping table specified with the <tt><ref id="option-t" name="-t"></tt> command line switch. Example: <tscreen><verb> .charmap $41, $61 ; Map 'A' to 'a' </verb></tscreen> <sect1><tt>.CODE</tt><label id=".CODE"> Switch to the CODE segment. The name of the CODE segment is always "CODE", so this is a shortcut for <tscreen><verb> .segment "CODE" </verb></tscreen> See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command. <sect1><tt>.CONDES</tt><label id=".CONDES"> Export a symbol and mark it in a special way. The linker is able to build tables of all such symbols. This may be used to automatically create a list of functions needed to initialize linked library modules. Note: The linker has a feature to build a table of marked routines, but it is your code that must call these routines, so just declaring a symbol with <tt/.CONDES/ does nothing by itself. All symbols are exported as an absolute (16 bit) symbol. You don't need to use an additional <tt><ref id=".EXPORT" name=".EXPORT"></tt> statement, this is implied by <tt/.CONDES/. <tt/.CONDES/ is followed by the type, which may be <tt/constructor/, <tt/destructor/ or a numeric value between 0 and 6 (where 0 is the same as specifiying <tt/constructor/ and 1 is equal to specifying <tt/destructor/). The <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands are actually shortcuts for <tt/.CONDES/ with a type of <tt/constructor/ resp. <tt/destructor/. After the type, an optional priority may be specified. Higher numeric values mean higher priority. If no priority is given, the default priority of 7 is used. Be careful when assigning priorities to your own module constructors so they won't interfere with the ones in the cc65 library. Example: <tscreen><verb> .condes ModuleInit, constructor .condes ModInit, 0, 16 </verb></tscreen> See the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section <ref id="condes" name="Module constructors/destructors"> explaining the feature in more detail. <sect1><tt>.CONSTRUCTOR</tt><label id=".CONSTRUCTOR"> Export a symbol and mark it as a module constructor. This may be used together with the linker to build a table of constructor subroutines that are called by the startup code. Note: The linker has a feature to build a table of marked routines, but it is your code that must call these routines, so just declaring a symbol as constructor does nothing by itself. A constructor is always exported as an absolute (16 bit) symbol. You don't need to use an additional <tt/.export/ statement, this is implied by <tt/.constructor/. It may have an optional priority that is separated by a comma. Higher numeric values mean a higher priority. If no priority is given, the default priority of 7 is used. Be careful when assigning priorities to your own module constructors so they won't interfere with the ones in the cc65 library. Example: <tscreen><verb> .constructor ModuleInit .constructor ModInit, 16 </verb></tscreen> See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> commands and the separate section <ref id="condes" name="Module constructors/destructors"> explaining the feature in more detail. <sect1><tt>.DATA</tt><label id=".DATA"> Switch to the DATA segment. The name of the DATA segment is always "DATA", so this is a shortcut for <tscreen><verb> .segment "DATA" </verb></tscreen> See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command. <sect1><tt>.DBYT</tt><label id=".DBYT"> Define word sized data with the hi and lo bytes swapped (use <tt/.WORD/ to create word sized data in native 65XX format). Must be followed by a sequence of (word ranged) expressions. Example: <tscreen><verb> .dbyt $1234, $4512 </verb></tscreen> This will emit the bytes <tscreen><verb> $12 $34 $45 $12 </verb></tscreen> into the current segment in that order. <sect1><tt>.DEBUGINFO</tt><label id=".DEBUGINFO"> Switch on or off debug info generation. The default is off (that is, the object file will not contain debug infos), but may be changed by the -g switch on the command line. The command must be followed by a '+' or '-' character to switch the option on or off respectively. Example: <tscreen><verb> .debuginfo + ; Generate debug info </verb></tscreen> <sect1><tt>.DEFINE</tt><label id=".DEFINE"> Start a define style macro definition. The command is followed by an identifier (the macro name) and optionally by a list of formal arguments in braces. See section <ref id="macros" name="Macros">. <sect1><tt>.DEF, .DEFINED</tt><label id=".DEFINED"> Builtin function. The function expects an identifier as argument in braces. The argument is evaluated, and the function yields "true" if the identifier is a symbol that is already defined somewhere in the source file up to the current position. Otherwise the function yields false. As an example, the <tt><ref id=".IFDEF" name=".IFDEF"></tt> statement may be replaced by <tscreen><verb> .if .defined(a) </verb></tscreen> <sect1><tt>.DESTRUCTOR</tt><label id=".DESTRUCTOR"> Export a symbol and mark it as a module destructor. This may be used together with the linker to build a table of destructor subroutines that are called by the startup code. Note: The linker has a feature to build a table of marked routines, but it is your code that must call these routines, so just declaring a symbol as constructor does nothing by itself. A destructor is always exported as an absolute (16 bit) symbol. You don't need to use an additional <tt/.export/ statement, this is implied by <tt/.destructor/. It may have an optional priority that is separated by a comma. Higher numerical values mean a higher priority. If no priority is given, the default priority of 7 is used. Be careful when assigning priorities to your own module destructors so they won't interfere with the ones in the cc65 library. Example: <tscreen><verb> .destructor ModuleDone .destructor ModDone, 16 </verb></tscreen> See the <tt><ref id=".CONDES" name=".CONDES"></tt> and <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> commands and the separate section <ref id="condes" name="Module constructors/destructors"> explaining the feature in more detail. <sect1><tt>.DWORD</tt><label id=".DWORD"> Define dword sized data (4 bytes) Must be followed by a sequence of expressions. Example: <tscreen><verb> .dword $12344512, $12FA489 </verb></tscreen> <sect1><tt>.ELSE</tt><label id=".ELSE"> Conditional assembly: Reverse the current condition. <sect1><tt>.ELSEIF</tt><label id=".ELSEIF"> Conditional assembly: Reverse current condition and test a new one. <sect1><tt>.END</tt><label id=".END"> Forced end of assembly. Assembly stops at this point, even if the command is read from an include file. <sect1><tt>.ENDENUM</tt><label id=".ENDENUM"> End a <tt><ref id=".ENUM" name=".ENUM"></tt> declaration. <sect1><tt>.ENDIF</tt><label id=".ENDIF"> Conditional assembly: Close a <tt><ref id=".IF" name=".IF..."></tt> or <tt><ref id=".ELSE" name=".ELSE"></tt> branch. <sect1><tt>.ENDMAC, .ENDMACRO</tt><label id=".ENDMACRO"> End of macro definition (see section <ref id="macros" name="Macros">). <sect1><tt>.ENDPROC</tt><label id=".ENDPROC"> End of local lexical level (see <tt><ref id=".PROC" name=".PROC"></tt>). <sect1><tt>.ENDREP, .ENDREPEAT</tt><label id=".ENDREPEAT"> End a <tt><ref id=".REPEAT" name=".REPEAT"></tt> block. <sect1><tt>.ENDSCOPE</tt><label id=".ENDSCOPE"> End of local lexical level (see <tt/<ref id=".SCOPE" name=".SCOPE">/). <sect1><tt>.ENDSTRUCT</tt><label id=".ENDSTRUCT"> Ends a struct definition. See the <tt/<ref id=".STRUCT" name=".STRUCT">/ command and the separate section named <ref id="structs" name=""Structs and unions"">. <sect1><tt>.ENUM</tt><label id=".ENUM"> Start an enumeration. This directive is very similar to the C <tt/enum/ keyword. If a name is given, a new scope is created for the enumeration, otherwise the enumeration members are placed in the enclosing scope. In the enumeration body, symbols are declared. The first symbol has a value of zero, and each following symbol will get the value of the preceeding plus one. This behaviour may be overriden by an explicit assignment. Two symbols may have the same value. Example: <tscreen><verb> .enum errorcodes no_error file_error parse_error .endenum </verb></tscreen> Above example will create a new scope named <tt/errorcodes/ with three symbols in it that get the values 0, 1 and 2 respectively. Another way to write this would have been: <tscreen><verb> .scope errorcodes no_error = 0 file_error = 1 parse_error = 2 .endscope </verb></tscreen> Please note that explicit scoping must be used to access the identifiers: <tscreen><verb> .word errorcodes::no_error </verb></tscreen> A more complex example: <tscreen><verb> .enum EUNKNOWN = -1 EOK EFILE EBUSY EAGAIN EWOULDBLOCK = EAGAIN .endenum </verb></tscreen> In this example, the enumeration does not have a name, which means that the members will be visible in the enclosing scope and can be used in this scope without explicit scoping. The first member (<tt/EUNKNOWN/) has the value -1. The value for the following members is incremented by one, so <tt/EOK/ would be zero and so on. <tt/EWOULDBLOCK/ is an alias for <tt/EGAIN/, so it has an override for the value using an already defined symbol. <sect1><tt>.ERROR</tt><label id=".ERROR"> Force an assembly error. The assembler will output an error message preceeded by "User error" and will <em/not/ produce an object file. This command may be used to check for initial conditions that must be set before assembling a source file. Example: <tscreen><verb> .if foo = 1 ... .elseif bar = 1 ... .else .error "Must define foo or bar!" .endif </verb></tscreen> See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref id=".OUT" name=".OUT"></tt> directives. <sect1><tt>.EXITMAC, .EXITMACRO</tt><label id=".EXITMACRO"> Abort a macro expansion immidiately. This command is often useful in recursive macros. See separate section <ref id="macros" name="Macros">. <sect1><tt>.EXPORT</tt><label id=".EXPORT"> Make symbols accessible from other modules. Must be followed by a comma separated list of symbols to export, with each one optionally followed by an address specification. The default is to export the symbol with the address size it actually has. The assembler will issue a warning, if the symbol is exported with an address size smaller than the actual address size. Example: <tscreen><verb> .export foo .export bar: far </verb></tscreen> See: <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt> <sect1><tt>.EXPORTZP</tt><label id=".EXPORTZP"> Make symbols accessible from other modules. Must be followed by a comma separated list of symbols to export. The exported symbols are explicitly marked as zero page symols. Example: <tscreen><verb> .exportzp foo, bar </verb></tscreen> See: <tt><ref id=".EXPORT" name=".EXPORT"></tt> <sect1><tt>.FARADDR</tt><label id=".FARADDR"> Define far (24 bit) address data. The command must be followed by a sequence of (not necessarily constant) expressions. Example: <tscreen><verb> .faraddr DrawCircle, DrawRectangle, DrawHexagon </verb></tscreen> See: <tt><ref id=".ADDR" name=".ADDR"></tt> <sect1><tt>.FEATURE</tt><label id=".FEATURE"> This directive may be used to enable one or more compatibility features of the assembler. While the use of <tt/.FEATURE/ should be avoided when possible, it may be useful when porting sources written for other assemblers. There is no way to switch a feature off, once you have enabled it, so using <tscreen><verb> .FEATURE xxx </verb></tscreen> will enable the feature until end of assembly is reached. The following features are available: <descrip> <tag><tt>at_in_identifiers</tt></tag> Accept the at character (`@') as a valid character in identifiers. The at character is not allowed to start an identifier, even with this feature enabled. <tag><tt>dollar_in_identifiers</tt></tag> Accept the dollar sign (`$') as a valid character in identifiers. The at character is not allowed to start an identifier, even with this feature enabled. <tag><tt>dollar_is_pc</tt></tag> The dollar sign may be used as an alias for the star (`*'), which gives the value of the current PC in expressions. Note: Assignment to the pseudo variable is not allowed. <tag><tt>labels_without_colons</tt></tag> Allow labels without a trailing colon. These labels are only accepted, if they start at the beginning of a line (no leading white space). <tag><tt>leading_dot_in_identifiers</tt></tag> Accept the dot (`.') as the first character of an identifier. This may be used for example to create macro names that start with a dot emulating control directives of other assemblers. Note however, that none of the reserved keywords built into the assembler, that starts with a dot, may be overridden. When using this feature, you may also get into trouble if later versions of the assembler define new keywords starting with a dot. <tag><tt>loose_char_term</tt></tag> Accept single quotes as well as double quotes as terminators for char constants. <tag><tt>loose_string_term</tt></tag> Accept single quotes as well as double quotes as terminators for string constants. <tag><tt>missing_char_term</tt></tag> Accept single quoted character constants where the terminating quote is missing. <tscreen><verb> lda #'a </verb></tscreen> <bf/Note:/ This does not work in conjunction with <tt/.FEATURE loose_string_term/, since in this case the input would be ambigous. <tag><tt>pc_assignment</tt></tag> Allow assignments to the PC symbol (`*' or `$' if <tt/dollar_is_pc/ is enabled). Such an assignment is handled identical to the <tt><ref id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just removing the lines with the assignments may also be an option when porting code written for older assemblers). <tag><tt>ubiquitous_idents</tt></tag> Allow the use of instructions names as names for macros and symbols. This makes it possible to "overload" instructions by defining a macro with the same name. This does also make it possible to introduce hard to find errors in your code, so be careful! </descrip> It is also possible to specify features on the command line using the <tt><ref id="option--feature" name="--feature"></tt> command line option. This is useful when translating sources written for older assemblers, when you don't want to change the source code. As an example, to translate sources written for Andre Fachats xa65 assembler, the features <verb> labels_without_colons, pc_assignment, loose_char_term </verb> may be helpful. They do not make ca65 completely compatible, so you may not be able to translate the sources without changes, even when enabling these features. However, I have found several sources that translate without problems when enabling these features on the command line. <sect1><tt>.FILEOPT, .FOPT</tt><label id=".FOPT"> Insert an option string into the object file. There are two forms of this command, one specifies the option by a keyword, the second specifies it as a number. Since usage of the second one needs knowledge of the internal encoding, its use is not recommended and I will only describe the first form here. The command is followed by one of the keywords <tscreen><verb> author comment compiler </verb></tscreen> a comma and a string. The option is written into the object file together with the string value. This is currently unidirectional and there is no way to actually use these options once they are in the object file. Examples: <tscreen><verb> .fileopt comment, "Code stolen from my brother" .fileopt compiler, "BASIC 2.0" .fopt author, "J. R. User" </verb></tscreen> <sect1><tt>.FORCEIMPORT</tt><label id=".FORCEIMPORT"> Import an absolute symbol from another module. The command is followed by a comma separated list of symbols to import. The command is similar to <tt> <ref id=".IMPORT" name=".IMPORT"></tt>, but the import reference is always written to the generated object file, even if the symbol is never referenced (<tt><ref id=".IMPORT" name=".IMPORT"></tt> will not generate import references for unused symbols). Example: <tscreen><verb> .forceimport needthisone, needthistoo </verb></tscreen> See: <tt><ref id=".IMPORT" name=".IMPORT"></tt> <sect1><tt>.GLOBAL</tt><label id=".GLOBAL"> Declare symbols as global. Must be followed by a comma separated list of symbols to declare. Symbols from the list, that are defined somewhere in the source, are exported, all others are imported. Additional <tt><ref id=".IMPORT" name=".IMPORT"></tt> or <tt><ref id=".EXPORT" name=".EXPORT"></tt> commands for the same symbol are allowed. Example: <tscreen><verb> .global foo, bar </verb></tscreen> <sect1><tt>.GLOBALZP</tt><label id=".GLOBALZP"> Declare symbols as global. Must be followed by a comma separated list of symbols to declare. Symbols from the list, that are defined somewhere in the source, are exported, all others are imported. Additional <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt> or <tt><ref id=".EXPORTZP" name=".EXPORTZP"></tt> commands for the same symbol are allowed. The symbols in the list are explicitly marked as zero page symols. Example: <tscreen><verb> .globalzp foo, bar </verb></tscreen> <sect1><tt>.I16</tt><label id=".I16"> Valid only in 65816 mode. Switch the index registers to 16 bit. Note: This command will not emit any code, it will tell the assembler to create 16 bit operands for immediate operands. See also the <tt><ref id=".I8" name=".I8"></tt> and <tt><ref id=".SMART" name=".SMART"></tt> commands. <sect1><tt>.I8</tt><label id=".I8"> Valid only in 65816 mode. Switch the index registers to 8 bit. Note: This command will not emit any code, it will tell the assembler to create 8 bit operands for immediate operands. See also the <tt><ref id=".I16" name=".I16"></tt> and <tt><ref id=".SMART" name=".SMART"></tt> commands. <sect1><tt>.IF</tt><label id=".IF"> Conditional assembly: Evalute an expression and switch assembler output on or off depending on the expression. The expression must be a constant expression, that is, all operands must be defined. A expression value of zero evaluates to FALSE, any other value evaluates to TRUE. <sect1><tt>.IFBLANK</tt><label id=".IFBLANK"> Conditional assembly: Check if there are any remaining tokens in this line, and evaluate to FALSE if this is the case, and to TRUE otherwise. If the condition is not true, further lines are not assembled until an <tt><ref id=".ELSE" name=".ESLE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive. This command is often used to check if a macro parameter was given. Since an empty macro parameter will evaluate to nothing, the condition will evaluate to FALSE if an empty parameter was given. Example: <tscreen><verb> .macro arg1, arg2 .ifblank arg2 lda #arg1 .else lda #arg2 .endif .endmacro </verb></tscreen> See also: <tt><ref id=".BLANK" name=".BLANK"></tt> <sect1><tt>.IFCONST</tt><label id=".IFCONST"> Conditional assembly: Evaluate an expression and switch assembler output on or off depending on the constness of the expression. A const expression evaluates to to TRUE, a non const expression (one containing an imported or currently undefined symbol) evaluates to FALSE. See also: <tt><ref id=".CONST" name=".CONST"></tt> <sect1><tt>.IFDEF</tt><label id=".IFDEF"> Conditional assembly: Check if a symbol is defined. Must be followed by a symbol name. The condition is true if the the given symbol is already defined, and false otherwise. See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt> <sect1><tt>.IFNBLANK</tt><label id=".IFNBLANK"> Conditional assembly: Check if there are any remaining tokens in this line, and evaluate to TRUE if this is the case, and to FALSE otherwise. If the condition is not true, further lines are not assembled until an <tt><ref id=".ELSE" name=".ELSE"></tt>, <tt><ref id=".ELSEIF" name=".ELSEIF"></tt> or <tt><ref id=".ENDIF" name=".ENDIF"></tt> directive. This command is often used to check if a macro parameter was given. Since an empty macro parameter will evaluate to nothing, the condition will evaluate to FALSE if an empty parameter was given. Example: <tscreen><verb> .macro arg1, arg2 lda #arg1 .ifnblank arg2 lda #arg2 .endif .endmacro </verb></tscreen> See also: <tt><ref id=".BLANK" name=".BLANK"></tt> <sect1><tt>.IFNDEF</tt><label id=".IFNDEF"> Conditional assembly: Check if a symbol is defined. Must be followed by a symbol name. The condition is true if the the given symbol is not defined, and false otherwise. See also: <tt><ref id=".DEFINED" name=".DEFINED"></tt> <sect1><tt>.IFNREF</tt><label id=".IFNREF"> Conditional assembly: Check if a symbol is referenced. Must be followed by a symbol name. The condition is true if if the the given symbol was not referenced before, and false otherwise. See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt> <sect1><tt>.IFP02</tt><label id=".IFP02"> Conditional assembly: Check if the assembler is currently in 6502 mode (see <tt><ref id=".P02" name=".P02"></tt> command). <sect1><tt>.IFP816</tt><label id=".IFP816"> Conditional assembly: Check if the assembler is currently in 65816 mode (see <tt><ref id=".P816" name=".P816"></tt> command). <sect1><tt>.IFPC02</tt><label id=".IFPC02"> Conditional assembly: Check if the assembler is currently in 65C02 mode (see <tt><ref id=".PC02" name=".PC02"></tt> command). <sect1><tt>.IFPSC02</tt><label id=".IFPSC02"> Conditional assembly: Check if the assembler is currently in 65SC02 mode (see <tt><ref id=".PSC02" name=".PSC02"></tt> command). <sect1><tt>.IFREF</tt><label id=".IFREF"> Conditional assembly: Check if a symbol is referenced. Must be followed by a symbol name. The condition is true if if the the given symbol was referenced before, and false otherwise. This command may be used to build subroutine libraries in include files (you may use separate object modules for this purpose too). Example: <tscreen><verb> .ifref ToHex ; If someone used this subroutine ToHex: tay ; Define subroutine lda HexTab,y rts .endif </verb></tscreen> See also: <tt><ref id=".REFERENCED" name=".REFERENCED"></tt> <sect1><tt>.IMPORT</tt><label id=".IMPORT"> Import a symbol from another module. The command is followed by a comma separated list of symbols to import, with each one optionally followed by an address specification. Example: <tscreen><verb> .import foo .import bar: zeropage </verb></tscreen> See: <tt><ref id=".IMPORTZP" name=".IMPORTZP"></tt> <sect1><tt>.IMPORTZP</tt><label id=".IMPORTZP"> Import a symbol from another module. The command is followed by a comma separated list of symbols to import. The symbols are explicitly imported as zero page symbols (that is, symbols with values in byte range). Example: <tscreen><verb> .importzp foo, bar </verb></tscreen> See: <tt><ref id=".IMPORT" name=".IMPORT"></tt> <sect1><tt>.INCBIN</tt><label id=".INCBIN"> Include a file as binary data. The command expects a string argument that is the name of a file to include literally in the current segment. In addition to that, a start offset and a size value may be specified, separated by commas. If no size is specified, all of the file from the start offset to end-of-file is used. If no start position is specified either, zero is assume (which means that the whole file is inserted). Example: <tscreen><verb> ; Include whole file .incbin "sprites.dat" ; Include file starting at offset 256 .incbin "music.dat", $100 ; Read 100 bytes starting at offset 200 .incbin "graphics.dat", 200, 100 </verb></tscreen> <sect1><tt>.INCLUDE</tt><label id=".INCLUDE"> Include another file. Include files may be nested up to a depth of 16. Example: <tscreen><verb> .include "subs.inc" </verb></tscreen> <sect1><tt>.LINECONT</tt><label id=".LINECONT"> Switch on or off line continuations using the backslash character before a newline. The option is off by default. Note: Line continuations do not work in a comment. A backslash at the end of a comment is treated as part of the comment and does not trigger line continuation. The command must be followed by a '+' or '-' character to switch the option on or off respectively. Example: <tscreen><verb> .linecont + ; Allow line continuations lda \ #$20 ; This is legal now </verb></tscreen> <sect1><tt>.LIST</tt><label id=".LIST"> Enable output to the listing. The command must be followed by a boolean switch ("on", "off", "+" or "-") and will enable or disable listing output. The option has no effect if the listing is not enabled by the command line switch -l. If -l is used, an internal counter is set to 1. Lines are output to the listing file, if the counter is greater than zero, and suppressed if the counter is zero. Each use of <tt/.LIST/ will increment or decrement the counter. Example: <tscreen><verb> .list on ; Enable listing output </verb></tscreen> <sect1><tt>.LISTBYTES</tt><label id=".LISTBYTES"> Set, how many bytes are shown in the listing for one source line. The default is 12, so the listing will show only the first 12 bytes for any source line that generates more than 12 bytes of code or data. The directive needs an argument, which is either "unlimited", or an integer constant in the range 4..255. Examples: <tscreen><verb> .listbytes unlimited ; List all bytes .listbytes 12 ; List the first 12 bytes .incbin "data.bin" ; Include large binary file </verb></tscreen> <sect1><tt>.LOCAL</tt><label id=".LOCAL"> This command may only be used inside a macro definition. It declares a list of identifiers as local to the macro expansion. A problem when using macros are labels: Since they don't change their name, you get a "duplicate symbol" error if the macro is expanded the second time. Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their name mapped to an internal unique name (<tt/___ABCD__/) with each macro invocation. Some other assemblers start a new lexical block inside a macro expansion. This has some drawbacks however, since that will not allow <em/any/ symbol to be visible outside a macro, a feature that is sometimes useful. The <tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way to address the problem. You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside a macro. <sect1><tt>.LOCALCHAR</tt><label id=".LOCALCHAR"> Defines the character that start "cheap" local labels. You may use one of '@' and '?' as start character. The default is '@'. Cheap local labels are labels that are visible only between two non cheap labels. This way you can reuse identifiers like "<tt/loop/" without using explicit lexical nesting. Example: <tscreen><verb> .localchar '?' Clear: lda #$00 ; Global label ?Loop: sta Mem,y ; Local label dey bne ?Loop ; Ok rts Sub: ... ; New global label bne ?Loop ; ERROR: Unknown identifier! </verb></tscreen> <sect1><tt>.MACPACK</tt><label id=".MACPACK"> Insert a predefined macro package. The command is followed by an identifier specifying the macro package to insert. Available macro packages are: <tscreen><verb> generic Defines generic macros like add and sub. longbranch Defines conditional long jump macros. cbm Defines the scrcode macro cpu Defines constants for the .CPU variable </verb></tscreen> Including a macro package twice, or including a macro package that redefines already existing macros will lead to an error. Example: <tscreen><verb> .macpack longbranch ; Include macro package cmp #$20 ; Set condition codes jne Label ; Jump long on condition </verb></tscreen> Macro packages are explained in more detail in section <ref id="macropackages" name="Macro packages">. <sect1><tt>.MAC, .MACRO</tt><label id=".MAC"> Start a classic macro definition. The command is followed by an identifier (the macro name) and optionally by a comma separated list of identifiers that are macro parameters. See section <ref id="macros" name="Macros">. <sect1><tt>.ORG</tt><label id=".ORG"> Start a section of absolute code. The command is followed by a constant expression that gives the new PC counter location for which the code is assembled. Use <tt><ref id=".RELOC" name=".RELOC"></tt> to switch back to relocatable code. Please note that you <em/do not need/ this command in most cases. Placing code at a specific address is the job of the linker, not the assembler, so there is usually no reason to assemble code to a specific address. You may not switch segments while inside a section of absolute code. Example: <tscreen><verb> .org $7FF ; Emit code starting at $7FF </verb></tscreen> <sect1><tt>.OUT</tt><label id=".OUT"> Output a string to the console without producing an error. This command is similiar to <tt/.ERROR/, however, it does not force an assembler error that prevents the creation of an object file. Example: <tscreen><verb> .out "This code was written by the codebuster(tm)" </verb></tscreen> See also the <tt><ref id=".WARNING" name=".WARNING"></tt> and <tt><ref id=".ERROR" name=".ERROR"></tt> directives. <sect1><tt>.P02</tt><label id=".P02"> Enable the 6502 instruction set, disable 65SC02, 65C02 and 65816 instructions. This is the default if not overridden by the <tt><ref id="option--cpu" name="--cpu"></tt> command line option. See: <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02" name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt> <sect1><tt>.P816</tt><label id=".P816"> Enable the 65816 instruction set. This is a superset of the 65SC02 and 6502 instruction sets. See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02" name=".PSC02"></tt> and <tt><ref id=".PC02" name=".PC02"></tt> <sect1><tt>.PAGELEN, .PAGELENGTH</tt><label id=".PAGELENGTH"> Set the page length for the listing. Must be followed by an integer constant. The value may be "unlimited", or in the range 32 to 127. The statement has no effect if no listing is generated. The default value is -1 (unlimited) but may be overridden by the <tt/--pagelength/ command line option. Beware: Since ca65 is a one pass assembler, the listing is generated after assembly is complete, you cannot use multiple line lengths with one source. Instead, the value set with the last <tt/.PAGELENGTH/ is used. Examples: <tscreen><verb> .pagelength 66 ; Use 66 lines per listing page .pagelength unlimited ; Unlimited page length </verb></tscreen> <sect1><tt>.PC02</tt><label id=".PC02"> Enable the 65C02 instructions set. This instruction set includes all 6502 and 65SC02 instructions. See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02" name=".PSC02"></tt> and <tt><ref id=".P816" name=".P816"></tt> <sect1><tt>.POPSEG</tt><label id=".POPSEG"> Pop the last pushed segment from the stack, and set it. This command will switch back to the segment that was last pushed onto the segment stack using the <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt> command, and remove this entry from the stack. The assembler will print an error message if the segment stack is empty when this command is issued. See: <tt><ref id=".PUSHSEG" name=".PUSHSEG"></tt> <sect1><tt>.PROC</tt><label id=".PROC"> Start a nested lexical level with the given name and adds a symbol with this name to the enclosing scope. All new symbols from now on are in the local lexical level and are accessible from outside only via <ref id="scopesyntax" name="explicit scope specification">. Symbols defined outside this local level may be accessed as long as their names are not used for new symbols inside the level. Symbols names in other lexical levels do not clash, so you may use the same names for identifiers. The lexical level ends when the <tt><ref id=".ENDPROC" name=".ENDPROC"></tt> command is read. Lexical levels may be nested up to a depth of 16 (this is an artificial limit to protect against errors in the source). Note: Macro names are always in the global level and in a separate name space. There is no special reason for this, it's just that I've never had any need for local macro definitions. Example: <tscreen><verb> .proc Clear ; Define Clear subroutine, start new level lda #$00 L1: sta Mem,y ; L1 is local and does not cause a ; duplicate symbol error if used in other ; places dey bne L1 ; Reference local symbol rts .endproc ; Leave lexical level </verb></tscreen> See: <tt/<ref id=".ENDPROC" name=".ENDPROC">/ and <tt/<ref id=".SCOPE" name=".SCOPE">/ <sect1><tt>.PSC02</tt><label id=".PSC02"> Enable the 65SC02 instructions set. This instruction set includes all 6502 instructions. See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt> and <tt><ref id=".P816" name=".P816"></tt> <sect1><tt>.PUSHSEG</tt><label id=".PUSHSEG"> Push the currently active segment onto a stack. The entries on the stack include the name of the segment and the segment type. The stack has a size of 16 entries. <tt/.PUSHSEG/ allows together with <tt><ref id=".POPSEG" name=".POPSEG"></tt> to switch to another segment and to restore the old segment later, without even knowing the name and type of the current segment. The assembler will print an error message if the segment stack is already full, when this command is issued. See: <tt><ref id=".POPSEG" name=".POPSEG"></tt> <sect1><tt>.REPEAT</tt><label id=".REPEAT"> Repeat all commands between <tt/.REPEAT/ and <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt> constant number of times. The command is followed by a constant expression that tells how many times the commands in the body should get repeated. Optionally, a comma and an identifier may be specified. If this identifier is found in the body of the repeat statement, it is replaced by the current repeat count (starting with zero for the first time the body is repeated). <tt/.REPEAT/ statements may be nested. If you use the same repeat count identifier for a nested <tt/.REPEAT/ statement, the one from the inner level will be used, not the one from the outer level. Example: The following macro will emit a string that is "encrypted" in that all characters of the string are XORed by the value $55. <tscreen><verb> .macro Crypt Arg .repeat .strlen(Arg), I .byte .strat(Arg, I) .xor $55 .endrep .endmacro </verb></tscreen> See: <tt><ref id=".ENDREPEAT" name=".ENDREPEAT"></tt> <sect1><tt>.RELOC</tt><label id=".RELOC"> Switch back to relocatable mode. See the <tt><ref id=".ORG" name=".ORG"></tt> command. <sect1><tt>.RES</tt><label id=".RES"> Reserve storage. The command is followed by one or two constant expressions. The first one is mandatory and defines, how many bytes of storage should be defined. The second, optional expression must by a constant byte value that will be used as value of the data. If there is no fill value given, the linker will use the value defined in the linker configuration file (default: zero). Example: <tscreen><verb> ; Reserve 12 bytes of memory with value $AA .res 12, $AA </verb></tscreen> <sect1><tt>.RODATA</tt><label id=".RODATA"> Switch to the RODATA segment. The name of the RODATA segment is always "RODATA", so this is a shortcut for <tscreen><verb> .segment "RODATA" </verb></tscreen> The RODATA segment is a segment that is used by the compiler for readonly data like string constants. See also the <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> command. <sect1><tt>.SCOPE</tt><label id=".SCOPE"> Start a nested lexical level with the given name. All new symbols from now on are in the local lexical level and are accessible from outside only via <ref id="scopesyntax" name="explicit scope specification">. Symbols defined outside this local level may be accessed as long as their names are not used for new symbols inside the level. Symbols names in other lexical levels do not clash, so you may use the same names for identifiers. The lexical level ends when the <tt><ref id=".ENDSCOPE" name=".ENDSCOPE"></tt> command is read. Lexical levels may be nested up to a depth of 16 (this is an artificial limit to protect against errors in the source). Note: Macro names are always in the global level and in a separate name space. There is no special reason for this, it's just that I've never had any need for local macro definitions. Example: <tscreen><verb> .scope Error ; Start new scope named Error None = 0 ; No error File = 1 ; File error Parse = 2 ; Parse error .endproc ; Close lexical level ... lda #Error::File ; Use symbol from scope Error </verb></tscreen> See: <tt/<ref id=".ENDSCOPE" name=".ENDSCOPE">/ and <tt/<ref id=".PROC" name=".PROC">/ <sect1><tt>.SEGMENT</tt><label id=".SEGMENT"> Switch to another segment. Code and data is always emitted into a segment, that is, a named section of data. The default segment is "CODE". There may be up to 254 different segments per object file (and up to 65534 per executable). There are shortcut commands for the most common segments ("CODE", "DATA" and "BSS"). The command is followed by a string containing the segment name (there are some constraints for the name - as a rule of thumb use only those segment names that would also be valid identifiers). There may also be an optional address size separated by a colon. See the section covering <tt/<ref id="address-sizes" name="address sizes">/ for more information. The default address size for a segment depends on the memory model specified on the command line. The default is "absolute", which means that you don't have to use an address size modifier in most cases. "absolute" means that the is a segment with 16 bit (absolute) addressing. That is, the segment will reside somewhere in core memory outside the zero page. "zeropage" (8 bit) means that the segment will be placed in the zero page and direct (short) addressing is possible for data in this segment. Beware: Only labels in a segment with the zeropage attribute are marked as reachable by short addressing. The `*' (PC counter) operator will work as in other segments and will create absolute variable values. Please note that a segment cannot have two different address sizes. A segment specified as zeropage cannot be declared as being absolute later. Examples: <tscreen><verb> .segment "ROM2" ; Switch to ROM2 segment .segment "ZP2": zeropage ; New direct segment .segment "ZP2" ; Ok, will use last attribute .segment "ZP2": absolute ; Error, redecl mismatch </verb></tscreen> See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE" name=".CODE"></tt>, <tt><ref id=".DATA" name=".DATA"></tt> and <tt><ref id=".RODATA" name=".RODATA"></tt> <sect1><tt>.SETCPU</tt><label id=".SETCPU"> Switch the CPU instruction set. The command is followed by a string that specifies the CPU. Possible values are those that can also be supplied to the <tt><ref id="option--cpu" name="--cpu"></tt> command line option, namely: 6502, 6502X, 65SC02, 65C02, 65816 and sunplus. Please note that support for the sunplus CPU is not available in the freeware version, because the instruction set of the sunplus CPU is "proprietary and confidential". See: <tt><ref id=".CPU" name=".CPU"></tt>, <tt><ref id=".IFP02" name=".IFP02"></tt>, <tt><ref id=".IFP816" name=".IFP816"></tt>, <tt><ref id=".IFPC02" name=".IFPC02"></tt>, <tt><ref id=".IFPSC02" name=".IFPSC02"></tt>, <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".P816" name=".P816"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, <tt><ref id=".PSC02" name=".PSC02"></tt> <sect1><tt>.SMART</tt><label id=".SMART"> Switch on or off smart mode. The command must be followed by a '+' or '-' character to switch the option on or off respectively. The default is off (that is, the assembler doesn't try to be smart), but this default may be changed by the -s switch on the command line. In smart mode the assembler will do the following: <itemize> <item>Track usage of the <tt/REP/ and <tt/SEP/ instructions in 65816 mode and update the operand sizes accordingly. If the operand of such an instruction cannot be evaluated by the assembler (for example, because the operand is an imported symbol), a warning is issued. Beware: Since the assembler cannot trace the execution flow this may lead to false results in some cases. If in doubt, use the <tt/.Inn/ and <tt/.Ann/ instructions to tell the assembler about the current settings. <item>In 65816 mode, replace a <tt/RTS/ instruction by <tt/RTL/ if it is used within a procedure declared as <tt/far/, or if the procedure has no explicit address specification, but it is <tt/far/ because of the memory model used. </itemize> Example: <tscreen><verb> .smart ; Be smart .smart - ; Stop being smart </verb></tscreen> See: <tt><ref id=".A16" name=".A16"></tt>, <tt><ref id=".A8" name=".A8"></tt>, <tt><ref id=".I16" name=".I16"></tt>, <tt><ref id=".I8" name=".I8"></tt> <sect1><tt>.STRUCT</tt><label id=".STRUCT"> Starts a struct definition. Structs are covered in a separate section named <ref id="structs" name=""Structs and unions"">. See: <tt><ref id=".ENDSTRUCT" name=".ENDSTRUCT"></tt> <sect1><tt>.SUNPLUS</tt><label id=".SUNPLUS"> Enable the SunPlus instructions set. This command will not work in the freeware version of the assembler, because the instruction set is "proprietary and confidential". See: <tt><ref id=".P02" name=".P02"></tt>, <tt><ref id=".PSC02" name=".PSC02"></tt>, <tt><ref id=".PC02" name=".PC02"></tt>, and <tt><ref id=".P816" name=".P816"></tt> <sect1><tt>.TAG</tt><label id=".TAG"> Allocate space for a struct or union. Example: <tscreen><verb> .struct Point xcoord .word ycoord .word .endstruct .bss .tag Point ; Allocate 4 bytes </verb></tscreen> <sect1><tt>.WARNING</tt><label id=".WARNING"> Force an assembly warning. The assembler will output a warning message preceeded by "User warning". This warning will always be output, even if other warnings are disabled with the <tt><ref id="option-W" name="-W0"></tt> command line option. This command may be used to output possible problems when assembling the source file. Example: <tscreen><verb> .macro jne target .local L1 .ifndef target .warning "Forward jump in jne, cannot optimize!" beq L1 jmp target L1: .else ... .endif .endmacro </verb></tscreen> See also the <tt><ref id=".ERROR" name=".ERROR"></tt> and <tt><ref id=".OUT" name=".OUT"></tt> directives. <sect1><tt>.WORD</tt><label id=".WORD"> Define word sized data. Must be followed by a sequence of (word ranged, but not necessarily constant) expressions. Example: <tscreen><verb> .word $0D00, $AF13, _Clear </verb></tscreen> <sect1><tt>.ZEROPAGE</tt><label id=".ZEROPAGE"> Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment. The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a shortcut for <tscreen><verb> .segment "ZEROPAGE", zeropage </verb></tscreen> Because of the "zeropage" attribute, labels declared in this segment are addressed using direct addressing mode if possible. You <em/must/ instruct the linker to place this segment somewhere in the address range 0..$FF otherwise you will get errors. See: <tt><ref id=".SEGMENT" name=".SEGMENT"></tt> <sect>Macros<label id="macros"> <sect1>Introduction Macros may be thought of as "parametrized super instructions". Macros are sequences of tokens that have a name. If that name is used in the source file, the macro is "expanded", that is, it is replaced by the tokens that were specified when the macro was defined. <sect1>Macros without parameters In it's simplest form, a macro does not have parameters. Here's an example: <tscreen><verb> .macro asr ; Arithmetic shift right cmp #$80 ; Put bit 7 into carry ror ; Rotate right with carry .endmacro </verb></tscreen> The macro above consists of two real instructions, that are inserted into the code, whenever the macro is expanded. Macro expansion is simply done by using the name, like this: <tscreen><verb> lda $2010 asr sta $2010 </verb></tscreen> <sect1>Parametrized macros When using macro parameters, macros can be even more useful: <tscreen><verb> .macro inc16 addr clc lda addr adc #$01 sta addr lda addr+1 adc #$00 sta addr+1 .endmacro </verb></tscreen> When calling the macro, you may give a parameter, and each occurence of the name "addr" in the macro definition will be replaced by the given parameter. So <tscreen><verb> inc16 $1000 </verb></tscreen> will be expanded to <tscreen><verb> clc lda $1000 adc #$01 sta $1000 lda $1000+1 adc #$00 sta $1000+1 </verb></tscreen> A macro may have more than one parameter, in this case, the parameters are separated by commas. You are free to give less parameters than the macro actually takes in the definition. You may also leave intermediate parameters empty. Empty parameters are replaced by empty space (that is, they are removed when the macro is exanded). If you have a look at our macro definition above, you will see, that replacing the "addr" parameter by nothing will lead to wrong code in most lines. To help you, writing macros with a variable parameter list, there are some control commands: <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> tests the rest of the line and returns true, if there are any tokens on the remainder of the line. Since empty parameters are replaced by nothing, this may be used to test if a given parameter is empty. <tt><ref id=".IFNBLANK" name=".IFNBLANK"></tt> tests the opposite. Look at this example: <tscreen><verb> .macro ldaxy a, x, y .ifnblank a lda #a .endif .ifnblank x ldx #x .endif .ifnblank y ldy #y .endif .endmacro </verb></tscreen> This macro may be called as follows: <tscreen><verb> ldaxy 1, 2, 3 ; Load all three registers ldaxy 1, , 3 ; Load only a and y ldaxy , , 3 ; Load y only </verb></tscreen> There's another helper command for determining, which macro parameters are valid: <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt> This command is replaced by the parameter count given, <em/including/ intermediate empty macro parameters: <tscreen><verb> ldaxy 1 ; .PARAMCOUNT = 1 ldaxy 1,,3 ; .PARAMCOUNT = 3 ldaxy 1,2 ; .PARAMCOUNT = 2 ldaxy 1, ; .PARAMCOUNT = 2 ldaxy 1,2,3 ; .PARAMCOUNT = 3 </verb></tscreen> Macro parameters may optionally be enclosed into curly braces. This allows the inclusion of tokens that would otherwise terminate the parameter (the comma in case of a macro parameter). <tscreen><verb> .macro foo arg1, arg2 ... .endmacro foo ($00,x) ; Two parameters passed foo {($00,x)} ; One parameter passed </verb></tscreen> In the first case, the macro is called with two parameters: '<tt/($00/' and 'x)'. The comma is not passed to the macro, since it is part of the calling sequence, not the parameters. In the second case, '($00,x)' is passed to the macro, this time including the comma. <sect1>Detecting parameter types Sometimes it is nice to write a macro that acts differently depending on the type of the argument supplied. An example would be a macro that loads a 16 bit value from either an immediate operand, or from memory. The <tt/<ref id=".MATCH" name=".MATCH">/ and <tt/<ref id=".XMATCH" name=".XMATCH">/ functions will allow you to do exactly this: <tscreen><verb> .macro ldax arg .if (.match (.left (1, {arg}), #)) ; immediate mode lda #<(.right (.tcount ({arg})-1, {arg})) ldx #>(.right (.tcount ({arg})-1, {arg})) .else ; assume absolute or zero page lda arg ldx 1+({arg}) .endif .endmacro </verb></tscreen> Using the <tt/<ref id=".MATCH" name=".MATCH">/ function, the macro is able to check if its argument begins with a hash mark. If so, two immediate loads are emitted, Otherwise a load from an absolute zero page memory location is assumed. Please note how the curly braces are used to enclose parameters to pseudo functions handling token lists. This is necessary, because the token lists may include commas or parens, which would be treated by the assembler as end-of-list. The macro can be used as <tscreen><verb> foo: .word $5678 ... ldax #$1234 ; X=$12, A=$34 ... ldax foo ; X=$56, A=$78 </verb></tscreen> <sect1>Recursive macros Macros may be used recursively: <tscreen><verb> .macro push r1, r2, r3 lda r1 pha .if .paramcount > 1 push r2, r3 .endif .endmacro </verb></tscreen> There's also a special macro to help writing recursive macros: <tt><ref id=".EXITMACRO" name=".EXITMACRO"></tt> This command will stop macro expansion immidiately: <tscreen><verb> .macro push r1, r2, r3, r4, r5, r6, r7 .ifblank r1 ; First parameter is empty .exitmacro .else lda r1 pha .endif push r2, r3, r4, r5, r6, r7 .endmacro </verb></tscreen> When expanding this macro, the expansion will push all given parameters until an empty one is encountered. The macro may be called like this: <tscreen><verb> push $20, $21, $32 ; Push 3 ZP locations push $21 ; Push one ZP location </verb></tscreen> <sect1>Local symbols inside macros Now, with recursive macros, <tt><ref id=".IFBLANK" name=".IFBLANK"></tt> and <tt><ref id=".PARAMCOUNT" name=".PARAMCOUNT"></tt>, what else do you need? Have a look at the inc16 macro above. Here is it again: <tscreen><verb> .macro inc16 addr clc lda addr adc #$01 sta addr lda addr+1 adc #$00 sta addr+1 .endmacro </verb></tscreen> If you have a closer look at the code, you will notice, that it could be written more efficiently, like this: <tscreen><verb> .macro inc16 addr inc addr bne Skip inc addr+1 Skip: .endmacro </verb></tscreen> But imagine what happens, if you use this macro twice? Since the label "Skip" has the same name both times, you get a "duplicate symbol" error. Without a way to circumvent this problem, macros are not as useful, as they could be. One solution is, to start a new lexical block inside the macro: <tscreen><verb> .macro inc16 addr .proc inc addr bne Skip inc addr+1 Skip: .endproc .endmacro </verb></tscreen> Now the label is local to the block and not visible outside. However, sometimes you want a label inside the macro to be visible outside. To make that possible, there's a new command that's only usable inside a macro definition: <tt><ref id=".LOCAL" name=".LOCAL"></tt>. <tt/.LOCAL/ declares one or more symbols as local to the macro expansion. The names of local variables are replaced by a unique name in each separate macro expansion. So we could also solve the problem above by using <tt/.LOCAL/: <tscreen><verb> .macro inc16 addr .local Skip ; Make Skip a local symbol clc lda addr adc #$01 sta addr bcc Skip inc addr+1 Skip: ; Not visible outside .endmacro </verb></tscreen> <sect1>C style macros Starting with version 2.5 of the assembler, there is a second macro type available: C style macros using the <tt/.DEFINE/ directive. These macros are similar to the classic macro type described above, but behaviour is sometimes different: <itemize> <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> may not span more than a line. You may use line continuation (see <tt><ref id=".LINECONT" name=".LINECONT"></tt>) to spread the definition over more than one line for increased readability, but the macro itself may not contain an end-of-line token. <item> Macros defined with <tt><ref id=".DEFINE" name=".DEFINE"></tt> share the name space with classic macros, but they are detected and replaced at the scanner level. While classic macros may be used in every place, where a mnemonic or other directive is allowed, <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros are allowed anywhere in a line. So they are more versatile in some situations. <item> <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may take parameters. While classic macros may have empty parameters, this is not true for <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros. For this macro type, the number of actual parameters must match exactly the number of formal parameters. To make this possible, formal parameters are enclosed in braces when defining the macro. If there are no parameters, the empty braces may be omitted. <item> Since <tt><ref id=".DEFINE" name=".DEFINE"></tt> style macros may not contain end-of-line tokens, there are things that cannot be done. They may not contain several processor instructions for example. So, while some things may be done with both macro types, each type has special usages. The types complement each other. </itemize> Let's look at a few examples to make the advantages and disadvantages clear. To emulate assemblers that use "<tt/EQU/" instead of "<tt/=/" you may use the following <tt/.DEFINE/: <tscreen><verb> .define EQU = foo EQU $1234 ; This is accepted now </verb></tscreen> You may use the directive to define string constants used elsewhere: <tscreen><verb> ; Define the version number .define VERSION "12.3a" ; ... and use it .asciiz VERSION </verb></tscreen> Macros with parameters may also be useful: <tscreen><verb> .define DEBUG(message) .out message DEBUG "Assembling include file #3" </verb></tscreen> Note that, while formal parameters have to be placed in braces, this is not true for the actual parameters. Beware: Since the assembler cannot detect the end of one parameter, only the first token is used. If you don't like that, use classic macros instead: <tscreen><verb> .macro message .out message .endmacro </verb></tscreen> (This is an example where a problem can be solved with both macro types). <sect1>Characters in macros When using the <ref id="option-t" name="-t"> option, characters are translated into the target character set of the specific machine. However, this happens as late as possible. This means that strings are translated if they are part of a <tt><ref id=".BYTE" name=".BYTE"></tt> or <tt><ref id=".ASCIIZ" name=".ASCIIZ"></tt> command. Characters are translated as soon as they are used as part of an expression. This behaviour is very intuitive outside of macros but may be confusing when doing more complex macros. If you compare characters against numeric values, be sure to take the translation into account. <sect>Macro packages<label id="macropackages"> Using the <tt><ref id=".MACPACK" name=".MACPACK"></tt> directive, predefined macro packages may be included with just one command. Available macro packages are: <sect1><tt>.MACPACK generic</tt> This macro package defines macros that are useful in almost any program. Currently, two macros are defined: <tscreen><verb> .macro add Arg clc adc Arg .endmacro .macro sub Arg sec sbc Arg .endmacro </verb></tscreen> <sect1><tt>.MACPACK longbranch</tt> This macro package defines long conditional jumps. They are named like the short counterpart but with the 'b' replaced by a 'j'. Here is a sample definition for the "<tt/jeq/" macro, the other macros are built using the same scheme: <tscreen><verb> .macro jeq Target .if .def(Target) .and ((*+2)-(Target) <= 127) beq Target .else bne *+5 jmp Target .endif .endmacro </verb></tscreen> All macros expand to a short branch, if the label is already defined (back jump) and is reachable with a short jump. Otherwise the macro expands to a conditional branch with the branch condition inverted, followed by an absolute jump to the actual branch target. The package defines the following macros: <tscreen><verb> jeq, jne, jmi, jpl, jcs, jcc, jvs, jvc </verb></tscreen> <sect1><tt>.MACPACK cbm</tt> The cbm macro package will define a macro named <tt/scrcode/. It takes a string as argument and places this string into memory translated into screen codes. <sect1><tt>.MACPACK cpu</tt> This macro package does not define any macros but constants used to examine the value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable. For each supported CPU a constant similar to <tscreen><verb> CPU_6502 CPU_65SC02 CPU_65C02 CPU_65816 CPU_SUNPLUS </verb></tscreen> is defined. These constants may be used to determine the exact type of the currently enabled CPU. In addition to that, for each CPU instruction set, another constant is defined: <tscreen><verb> CPU_ISET_6502 CPU_ISET_65SC02 CPU_ISET_65C02 CPU_ISET_65816 CPU_ISET_SUNPLUS </verb></tscreen> The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the currently enabled CPU supports a specific instruction set. For example the 65C02 supports all instructions of the 65SC02 CPU, so it has the <tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/ bit. Using <tscreen><verb> .if (.cpu .bitand CPU_ISET_65SC02) lda (sp) .else ldy #$00 lda (sp),y .endif </verb></tscreen> it is possible to determine if the <tscreen><verb> lda (sp) </verb></tscreen> instruction is supported, which is the case for the 65SC02, 65C02 and 65816 CPUs (the latter two are upwards compatible to the 65SC02). <sect>Structs and unions<label id="structs"> Structs and unions are special forms of <ref id="scopes" name="scopes">. They are to some degree comparable to their C counterparts. Both have a list of members. Each member allocates storage and may optionally have a name, which, in case of a struct, is the offset from the beginning and, in case of a union, is always zero. Here is an example for a very simple struct with two members and a total size of 4 bytes: <tscreen><verb> .struct Point xcoord .word ycoord .word .endstruct </verb></tscreen> A union shares the total space between all its members, its size is the same as that of the largest member. A struct or union must not necessarily have a name. If it is anonymous, no local scope is opened, the identifiers used to name the members are placed into the current scope instead. A struct may contain unnamed members and definitions of local structs. The storage allocators may contain a multiplier, as in the example below: <tscreen><verb> .struct Circle .struct Point .word 2 ; Allocate two words .endstruct Radius .word .endstruct </verb></tscreen> Using the <ref id=".TAG" name=".TAG"> keyword, it is possible to embedd already defined structs or unions in structs: <tscreen><verb> .struct Point xcoord .word ycoord .word .endstruct .struct Circle Origin .tag Point Radius .byte .endstruct </verb></tscreen> Space for a struct or union may be allocated using the <ref id=".TAG" name=".TAG"> directive. <tscreen><verb> C: .tag Circle </verb></tscreen> Currently, members are just offsets from the start of the struct or union. To access a field of a struct, the member offset has to be added to the address of the struct itself: <tscreen><verb> lda C+Circle::Radius ; Load circle radius into A </verb></tscreen> This may change in a future version of the assembler. <sect>Module constructors/destructors<label id="condes"> Note: This section applies mostly to C programs, so the explanation below uses examples from the C libraries. However, the feature may also be useful for assembler programs. <sect1>Module overview Using the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> keywords it it possible to export functions in a special way. The linker is able to generate tables with all functions of a specific type. Such a table will only include symbols from object files that are linked into a specific executable. This may be used to add initialization and cleanup code for library modules. The C heap functions are an example where module initialization code is used. All heap functions (<tt>malloc</tt>, <tt>free</tt>, ...) work with a few variables that contain the start and the end of the heap, pointers to the free list and so on. Since the end of the heap depends on the size and start of the stack, it must be initialized at runtime. However, initializing these variables for programs that do not use the heap are a waste of time and memory. So the central module defines a function that contains initialization code and exports this function using the <tt/.CONSTRUCTOR/ statement. If (and only if) this module is added to an executable by the linker, the initialization function will be placed into the table of constructors by the linker. The C startup code will call all constructors before <tt/main/ and all destructors after <tt/main/, so without any further work, the heap initialization code is called once the module is linked in. While it would be possible to add explicit calls to initialization functions in the startup code, the new approach has several advantages: <enum> <item> If a module is not included, the initialization code is not linked in and not called. So you don't pay for things you don't need. <item> Adding another library that needs initialization does not mean that the startup code has to be changed. Before we had module constructors and destructors, the startup code for all systems had to be adjusted to call the new initialization code. <item> The feature saves memory: Each additional initialization function needs just two bytes in the table (a pointer to the function). </enum> <sect1>Calling order Both, constructors and destructors are sorted in increasing priority order by the linker when using one of the builtin linker configurations, so the functions with lower priorities come first and are followed by those with higher priorities. The C library runtime subroutine that walks over the constructor and destructor tables calls the functions starting from the top of the table - which means that functions with a high priority are called first. So when using the C runtime, both constructors and destructors are called with high priority functions first, followed by low priority functions. <sect1>Pitfalls When creating and using module constructors and destructors, please take care of the following: <itemize> <item> The linker will only generate function tables, it will not generate code to call these functions. If you're using the feature in some other than the existing C environments, you have to write code to call all functions in a linker generated table yourself. See the <tt>condes</tt> module in the C runtime for an example on how to do this. <item> The linker will only add addresses of functions that are in modules linked to the executable. This means that you have to be careful where to place the condes functions. If initialization is needed for a group of functions, be sure to place the initialization function into a module that is linked in regardless of which function is called by the user. <item> The linker will generate the tables only when requested to do so by the <tt/FEATURE CONDES/ statement in the linker config file. Each table has to be requested separately. <item> Constructors and destructors may have priorities. These priorities determine the order of the functions in the table. If your intialization or cleanup code does depend on other initialization or cleanup code, you have to choose the priority for the functions accordingly. <item> Besides the <tt><ref id=".CONSTRUCTOR" name=".CONSTRUCTOR"></tt> and <tt><ref id=".DESTRUCTOR" name=".DESTRUCTOR"></tt> statements, there is also a more generic command: <tt><ref id=".CONDES" name=".CONDES"></tt>. This allows to specify an additional type. Predefined types are 0 (constructor) and 1 (destructor). The linker generates a separate table for each type on request. </itemize> <sect>Porting sources from other assemblers Sometimes it is necessary to port code written for older assemblers to ca65. In some cases, this can be done without any changes to the source code by using the emulation features of ca65 (see <tt><ref id=".FEATURE" name=".FEATURE"></tt>). In other cases, it is necessary to make changes to the source code. Probably the biggest difference is the handling of the <tt><ref id=".ORG" name=".ORG"></tt> directive. ca65 generates relocatable code, and placement is done by the linker. Most other assemblers generate absolute code, placement is done within the assembler and there is no external linker. In general it is not a good idea to write new code using the emulation features of the assembler, but there may be situations where even this rule is not valid. <sect1>TASS You need to use some of the ca65 emulation features to simulate the behaviour of such simple assemblers. <enum> <item>Prepare your sourcecode like this: <tscreen><verb> ; if you want TASS style labels without colons .feature labels_without_colons ; if you want TASS style character constants ; ("a" instead of the default 'a') .feature loose_char_term .word *+2 ; the cbm load address [yourcode here] </verb></tscreen> notice that the two emulation features are mostly useful for porting sources originally written in/for TASS, they are not needed for the actual "simple assembler operation" and are not recommended if you are writing new code from scratch. <item>Replace all program counter assignments (which are not possible in ca65 by default, and the respective emulation feature works different from what you'd expect) by another way to skip to another memory location, for example the <tt><ref id=".RES" name=".RES"></tt>directive. <tscreen><verb> ; *=$2000 .res $2000-* ; reserve memory up to $2000 </verb></tscreen> notice that other than the original TASS, ca65 can never move the programmcounter backwards - think of it as if you are assembling to disc with TASS. <item>Conditional assembly (<tt/.ifeq//<tt/.endif//<tt/.goto/ etc.) must be rewritten to match ca65 syntax. Most importantly notice that due to the lack of <tt/.goto/, everything involving loops must be replaced by <tt><ref id=".REPEAT" name=".REPEAT"></tt>. <item>To assemble code to a different address than it is executed at, use the <tt><ref id=".ORG" name=".ORG"></tt> directive instead of <tt/.offs/-constructs. <tscreen><verb> .org $1800 [floppy code here] .reloc ; back to normal </verb></tscreen> <item>Then assemble like this: <tscreen><verb> cl65 --start-addr 0x0ffe -t none myprog.s -o myprog.prg </verb></tscreen> notice that you need to use the actual start address minus two, since two bytes are used for the cbm load address. </enum> <sect>Bugs/Feedback If you have problems using the assembler, if you find any bugs, or if you're doing something interesting with the assembler, I would be glad to hear from you. Feel free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">). <sect>Copyright ca65 (and all cc65 binutils) are (C) Copyright 1998-2003 Ullrich von Bassewitz. For usage of the binaries and/or sources the following conditions do apply: This software is provided 'as-is', without any expressed or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software. Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions: <enum> <item> The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required. <item> Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. <item> This notice may not be removed or altered from any source distribution. </enum> </article>