ca65 Users Guide <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org"> <date>19.07.2000 <abstract> ca65 is a 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. 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 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 The assembler accepts the following options: <tscreen><verb> --------------------------------------------------------------------------- Usage: ca65 [options] file Short options: -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 -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 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 --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> Here is a description of all the command line options: <descrip> <tag><tt>--cpu type</tt></tag> Set the default for the CPU type. The option takes a parameter, which may be one of 6502, 65C02, 65816 and sunplus The latter (sunplus) is not available in the freeware version, because the instruction set of the sunplus CPU is "confidential". <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/.FEATURE/ command for a list of emulation features. <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/.CASE/ control command (see section 6). <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>-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/.PAGELENGTH/ directive for more information. <tag><tt>-s, --smart-mode</tt></tag> In smart mode (enabled by -s or the <tt/.SMART/ pseudo instruction) the assembler will track usage of the REP and 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. <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/.AUTOIMPORT/, see control command section below) 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. <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 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 6 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 all valid 6502 mnemonics when in 6502 mode (the default). The assembler accepts all valid 65SC02 mnemonics when in 65SC02 mode (after a <tt/.PC02/ command is found). The assembler accepts all valid 65816 mnemonics with a few exceptions after a .P816 command is found. These exceptions are listed below. 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> Evaluation of banked expressions in 65816 mode differs slightly from the official syntax: Instead of accepting a 24 bit address (something that is difficult for the assembler to determine and would have required one more special .import command), the bank and the absolute address in that bank are separated by a dot: <tscreen><verb> jsl 3.$1234 ; Call subroutine at $1234 in bank 3 </verb></tscreen> For literal values, the assembler accepts the widely used number formats: A preceeding '$' 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. <sect>Expressions 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. 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 '>'/'<' 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. <bf>Boolean expressions:</bf> 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. Available operators sorted by precedence: <tscreen><verb> Op Description Precedence ------------------------------------------------------------------- .CONCAT Builtin function 0 .LEFT Builtin function 0 .MID Builtin function 0 .RIGHT Builtin function 0 .STRING Builtin function 0 * Builtin pseudo variable (r/o) 1 .BLANK Builtin function 1 .CONST Builtin function 1 .CPU Builtin pseudo variable (r/o) 1 .DEFINED Builtin function 1 .MATCH Builtin function 1 .TCOUNT Builtin function 1 .XMATCH Builtin function 1 .PARAMCOUNT Builtin pseudo variable (r/o) 1 .REFERENCED Builtin function 1 :: Global namespace override 1 + Unary plus 1 - Unary minus 1 ~ Unary bitwise not 1 .BITNOT Unary bitwise not 1 < Low byte operator 1 > High 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 2 .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. Some of the pseudo variables mentioned above need some more explanation: <tscreen><verb> * This symbol is replaced by the value of the program counter at start of the current instruction. Note, that '*' yields a rvalue, that means, you cannot assign to it. Use <tt/.ORG/ to set the program counter in sections with absolute code. </verb></tscreen> <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. <descrip> <tag/Numeric constants/ Numeric constants are defined using the equal sign. 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. An example would be <tscreen><verb> four = two * two </verb></tscreen> <tag/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. <tag/Local labels and symbols/ Using the <tt/.PROC/ directive, it is possible to create regions of code where the names of labels and symbols are local to this region. They are not know outside and cannot be accessed from there. Such regions may be nested like PROCEDUREs in Pascal. See the description of the <tt/.PROC/ directive for more information. <tag/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/.LOCALCHAR/ directive). Cheap local labels are visible only between two no cheap labels. As soon as a standard symbol is encountered (this may also be a local symbol if inside a region defined with the .PROC 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 #$20 @Loop: sta Mem,y ; Local label dey bne @Loop ; Ok rts Sub: ... ; New global label bne @Loop ; ERROR: Unknown identifier! </verb></tscreen> <tag/Unnamed labels/ If you really want to write messy code, there are also unnamed labels. These labels do not have a name (you guessed that already, didn't you?). A colon is used to mark the absence of the name. Unnamed labels may be accessed by using the colon plus several minus or plus characters as a label designator. Using the '-' characters will create a back reference (use the n'th label backwards), using '+' will create a forward reference (use the n'th label in forward direction). An example will help to understand this: <tscreen><verb> : lda (ptr1),y ; #1 cmp (ptr2),y bne :+ ; -> #2 tax beq :+++ ; -> #4 iny bne :- ; -> #1 inc ptr1+1 inc ptr2+1 bne :- ; -> #1 : bcs :+ ; #2 -> #3 ldx #$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. <tag/Using macros to define labels and constants/ While there are drawbacks with this approach, it may be handy in some situations. Using <tt/.DEFINE/, 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> </descrip> If <tt/.DEBUGINFO/ is enabled (or -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>Control commands Here's a list of all control commands and a description, what they do: <descrip> <tag><tt><idx>.A16</idx></tt></tag> 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/.SMART/ <tag><tt><idx>.A8</idx></tt></tag> 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/.SMART/ <tag><tt><idx>.ADDR</idx></tt></tag> 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/.FARADDR/. The command must be followed by a sequence of (not necessarily constant) expressions. Example: <tscreen><verb> .addr $0D00, $AF13, _Clear </verb></tscreen> <tag><tt><idx>.ALIGN</idx></tt></tag> 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> <tag><tt><idx>.ASCIIZ</idx></tt></tag> 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). <tag><tt><idx>.AUTOIMPORT</idx></tt></tag> Is followd 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> <tag><tt><idx>.BLANK</idx></tt></tag> 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. As an example, the <tt/.IFBLANK/ statement may be replaced by <tscreen><verb> .if .blank(arg) </verb></tscreen> <tag><tt><idx>.BSS</idx></tt></tag> 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/.SEGMENT/ command. <tag><tt><idx>.BYTE</idx></tt></tag> Define byte sized data. Must be followed by a sequence of (byte ranged) expressions or strings. Example: <tscreen><verb> .byte "Hello world", $0D, $00 </verb></tscreen> <tag><tt><idx>.CASE</idx></tt></tag> 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> <tag><tt><idx>.CODE</idx></tt></tag> 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/.SEGMENT/ command. <tag><tt><idx>.CONCAT</idx></tt></tag> Builtin 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> <tag><tt><idx>.CONST</idx></tt></tag> 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> <tag><tt><idx>.CPU</idx></tt></tag> Reading this pseudo variable will give a constant integer value that tells which instruction set is currently enabled. Possible values are: <tscreen><verb> 0 --> 6502 1 --> 65SC02 2 --> 65SC816 3 --> SunPlus SPC </verb></tscreen> It may be used to replace the .IFPxx pseudo instructions or to construct even more complex expressions. Example: <tscreen><verb> .if (.cpu = 0) .or (.cpu = 1) txa pha tya pha .else phx phy .endif </verb></tscreen> <tag><tt><idx>.DATA</idx></tt></tag> 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/.SEGMENT/ command. <tag><tt><idx>.DBYT</idx></tt></tag> 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. <tag><tt><idx>.DEBUGINFO</idx></tt></tag> 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> <tag><tt><idx>.DEFINE</idx></tt></tag> 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 separate section about macros. <tag><tt><idx>.DEF,</idx> <idx>.DEFINED</idx></tt></tag> 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/.IFDEF/ statement may be replaced by <tscreen><verb> .if .defined(a) </verb></tscreen> <tag><tt><idx>.DWORD</idx></tt></tag> Define dword sized data (4 bytes) Must be followed by a sequence of expressions. Example: <tscreen><verb> .dword $12344512, $12FA489 </verb></tscreen> <tag><tt><idx>.ELSE</idx></tt></tag> Conditional assembly: Reverse the current condition. <tag><tt><idx>.ELSEIF</idx></tt></tag> Conditional assembly: Reverse current condition and test a new one. <tag><tt><idx>.END</idx></tt></tag> Forced end of assembly. Assembly stops at this point, even if the command is read from an include file. <tag><tt><idx>.ENDIF</idx></tt></tag> Conditional assembly: Close a <tt/.IF.../ or <tt/.ELSE/ branch. <tag><tt><idx>.ENDMAC,</idx> <idx>.ENDMACRO</idx></tt></tag> End of macro definition (see separate section). <tag><tt><idx>.ENDPROC</idx></tt></tag> End of local lexical level (see <tt/.PROC/). <tag><tt><idx>.ENDREP,</idx> <idx>.ENDREPEAT</idx></tt></tag> End a <tt/.REPEAT/ block. See the <tt/.REPEAT/ command. <tag><tt><idx>.ERROR</idx></tt></tag> 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/.WARNING/ and <tt/.OUT/ directives. <tag><tt><idx>.EXITMAC,</idx> <idx>.EXITMACRO</idx></tt></tag> Abort a macro expansion immidiately. This command is often useful in recursive macros. See separate chapter about macros. <tag><tt><idx>.EXPORT</idx></tt></tag> Make symbols accessible from other modules. Must be followed by a comma separated list of symbols to export. Example: <tscreen><verb> .export foo, bar </verb></tscreen> <tag><tt><idx>.EXPORTZP</idx></tt></tag> 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> <tag><tt><idx>.FARADDR</idx></tt></tag> 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> <tag><tt><idx>.FEATURE</idx></tt></tag> 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><idx>dollar_is_pc</idx></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><idx>labels_without_colons</idx></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><idx>loose_string_term</idx></tt></tag> Accept single quotes as well as double quotes as terminators for string constants. <tag><tt><idx>at_in_identifiers</idx></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><idx>dollar_in_identifiers</idx></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><idx>pc_assignment</idx></tt></tag> Allow assignments to the PC symbol (`*' or `$' if dollar_is_pc is enabled). Such an assignment is handled identical to the <tt/.ORG/ 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). </descrip> <tag><tt><idx>.FILEOPT,</idx> <idx>.FOPT</idx></tt></tag> 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> <tag><tt><idx>.GLOBAL</idx></tt></tag> 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. An additional explicit <tt/.IMPORT/ or <tt/.EXPORT/ command for the same symbol is allowed. Example: <tscreen><verb> .global foo, bar </verb></tscreen> <tag><tt><idx>.GLOBALZP</idx></tt></tag> 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. An additional explicit <tt/.IMPORT/ or <tt/.EXPORT/ command for the same symbol is explicitly allowed. The symbols in the list are explicitly marked as zero page symols. Example: <tscreen><verb> .globalzp foo, bar </verb></tscreen> <tag><tt><idx>.I16</idx></tt></tag> 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/.SMART/ command. <tag><tt><idx>.I8</idx></tt></tag> 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/.SMART/ command. <tag><tt><idx>.IF</idx></tt></tag> 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. <tag><tt><idx>.IFBLANK</idx></tt></tag> 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/.ELSE/, <tt/.ELSEIF/ or <tt/.ENDIF/ 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/.BLANK/ <tag><tt><idx>.IFCONST</idx></tt></tag> 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/.CONST/ <tag><tt><idx>.IFDEF</idx></tt></tag> 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/.DEFINED/ <tag><tt><idx>.IFNBLANK</idx></tt></tag> 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/.ELSE/, <tt/.ELSEIF/ or <tt/.ENDIF/ 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/.BLANK/ <tag><tt><idx>.IFNDEF</idx></tt></tag> 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/.DEFINED/ <tag><tt><idx>.IFNREF</idx></tt></tag> 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/.REFERENCED/ <tag><tt><idx>.IFP02</idx></tt></tag> Conditional assembly: Check if the assembler is currently in 6502 mode (see <tt/.P02/ command). <tag><tt><idx>.IFP816</idx></tt></tag> Conditional assembly: Check if the assembler is currently in 65816 mode (see <tt/.P816/ command). <tag><tt><idx>.IFPC02</idx></tt></tag> Conditional assembly: Check if the assembler is currently in 65C02 mode (see <tt/.PC02/ command). <tag><tt><idx>.IFREF</idx></tt></tag> 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/.REFERENCED/ <tag><tt><idx>.IMPORT</idx></tt></tag> Import a symbol from another module. The command is followed by a comma separated list of symbols to import. Example: <tscreen><verb> .import foo, bar </verb></tscreen> <tag><tt><idx>.IMPORTZP</idx></tt></tag> 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> .includezp foo, bar </verb></tscreen> <tag><tt><idx>.INCBIN</idx></tt></tag> 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. Example: <tscreen><verb> .incbin "sprites.dat" </verb></tscreen> <tag><tt><idx>.INCLUDE</idx></tt></tag> Include another file. Include files may be nested up to a depth of 16. Example: <tscreen><verb> .include "subs.inc" </verb></tscreen> <tag><tt><idx>.LEFT</idx></tt></tag> 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. 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/.MID/ and <tt/.RIGHT/ builtin functions. <tag><tt><idx>.LINECONT</idx></tt></tag> 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> <tag><tt><idx>.LIST</idx></tt></tag> 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> <tag><tt><idx>.LISTBYTES</idx></tt></tag> 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> <tag><tt><idx>.LOCAL</idx></tt></tag> 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/.LOCAL/ 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/.LOCAL/ command is in my eyes a better way to address the problem. You get an error when using <tt/.LOCAL/ outside a macro. <tag><tt><idx>.LOCALCHAR</idx></tt></tag> 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> <tag><tt><idx>.MACPACK</idx></tt></tag> Insert a predefined macro package. The command is followed by an identifier specifying the macro package to insert. Available macro packages are: generic Defines generic macros like add and sub. longbranch Defines conditional long jump macros. 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> See separate section about macros packages. <tag><tt><idx>.MAC,</idx> <idx>.MACRO</idx></tt></tag> 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 separate section about macros. <tag><tt><idx>.MATCH</idx></tt></tag> 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> 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/.XMATCH/ 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/.MATCH/ 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 ; Shit carry into bit 7 .endmacro </verb></tscreen> The macro will only accept no arguments, or one argument that must be the reserved keyword "A". <tag><tt><idx>.MID</idx></tt></tag> 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. 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/.LEFT/ and <tt/.RIGHT/ builtin functions. <tag><tt><idx>.ORG</idx></tt></tag> 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/.RELOC/ to switch back to relocatable code. You may not switch segments while inside a section of absolute code. Example: <tscreen><verb> .org $7FF ; Emit code starting at $7FF </verb></tscreen> <tag><tt><idx>.OUT</idx></tt></tag> 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/.WARNING/ and <tt/.ERROR/ directives. <tag><tt><idx>.P02</idx></tt></tag> Enable the 6502 instruction set, disable 65C02 and 65816 instructions. This is the default if not overridden by the <tt/--cpu/ command line option. <tag><tt><idx>.P816</idx></tt></tag> Enable the 65816 instruction set. This is a superset of the 65C02 and 6502 instruction sets. <tag><tt><idx>.PAGELEN,</idx> <idx>.PAGELENGTH</idx></tt></tag> 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 but may be overridden by the <tt/--pagelength/ command line option. Beware: Since 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> <tag><tt><idx>.PARAMCOUNT</idx></tt></tag> 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> <tag><tt><idx>.PC02</idx></tt></tag> Enable the 65C02 instructions set. This instruction set includes all 6502 instructions. <tag><tt><idx>.PROC</idx></tt></tag> Start a nested lexical level. All new symbols from now on are in the local lexical level and are not accessible from outside. 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/.ENDPROC/ command is read. Lexical levels may be nested up to a depth of 16. The command may be followed by an identifier, in this case the identifier is declared in the outer level as a label having the value of the program counter at the start of the lexical level. 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> <tag><tt><idx>.REF,</idx> <idx>.REFERENCED</idx></tt></tag> 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/.IFREF/ statement may be replaced by <tscreen><verb> .if .referenced(a) </verb></tscreen> <tag><tt><idx>.REPEAT</idx></tt></tag> Repeat all commands between <tt/.REPEAT/ and <tt/.ENDREPEAT/ a 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> <tag><tt><idx>.RELOC</idx></tt></tag> Switch back to relocatable mode. See the <tt/.ORG/ command. <tag><tt><idx>.RES</idx></tt></tag> 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> <tag><tt><idx>.RIGHT</idx></tt></tag> 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. See also the <tt/.LEFT/ and <tt/.MID/ builtin functions. <tag><tt><idx>.RODATA</idx></tt></tag> 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/.SEGMENT/ command. <tag><tt><idx>.SEGMENT</idx></tt></tag> 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 attribute separated by a comma. Valid attributes are "<tt/zeropage/" and "<tt/absolute/". When specifying a segment for the first time, "absolute" is the default. For all other uses, the attribute specified the first time is the default. "absolute" means that this is a segment with absolute addressing. That is, the segment will reside somewhere in core memory outside the zero page. "zeropage" means the opposite: 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. Example: <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> <tag><tt><idx>.SMART</idx></tt></tag> 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 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. Example: <tscreen><verb> .smart ; Be smart .smart - ; Stop being smart </verb></tscreen> <tag><tt><idx>.STRAT</idx></tt></tag> 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> <tag><tt><idx>.STRING</idx></tt></tag> 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> <tag><tt><idx>.STRLEN</idx></tt></tag> 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> <tag><tt><idx>.TCOUNT</idx></tt></tag> Builtin function. The function accepts a token list in braces. The function result is the number of tokens given as argument. 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> <tag><tt><idx>.WARNING</idx></tt></tag> 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/-W0/ 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/.ERROR/ and <tt/.OUT/ directives. <tag><tt><idx>.WORD</idx></tt></tag> Define word sized data. Must be followed by a sequence of (word ranged, but not necessarily constant) expressions. Example: <tscreen><verb> .word $0D00, $AF13, _Clear </verb></tscreen> <tag><tt><idx>.ZEROPAGE</idx></tt></tag> Switch to the ZEROPAGE segment and mark it as direct (zeropage) segment. The name of the ZEROPAGE segment is always "ZEROPAGE", so this is a shortcut for <tscreen><verb> .segment "ZEROPAGE", zeropage </verb></tscreen> Because of the "zeropage" attribute, labels declared in this segment are addressed using direct addressing mode if possible. You <em/must/ instruct the linker to place this segment somewhere in the address range 0..$FF otherwise you will get errors. </descrip> <sect>Macros 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. 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> 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/.IFBLANK/ 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/.IFNBLANK/ 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/.PARAMCOUNT/. 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> 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/.EXITMACRO/. 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> Now, with recursive macros, <tt/.IFBLANK/ and <tt/.PARAMCOUNT/, 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 clc lda addr adc #$01 sta addr bcc 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 clc lda addr adc #$01 sta addr bcc 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/.LOCAL/. <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> 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 speified above, but behaviour is sometimes different: <itemize> <item> Macros defined with <tt/.DEFINE/ may not span more than a line. You may use line continuation (see <tt/.LINECONT/) to spread the definition over more than one line for increased readability, but the macro itself does not contain an end-of-line token. <item> Macros defined with <tt/.DEFINE/ 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/.DEFINE/ style macros are allowed anywhere in a line. So they are more versatile in some situations. <item> <tt/.DEFINE/ style macros may take parameters. While classic macros may have empty parameters, this is not true for <tt/.DEFINE/ 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/.DEFINE/ 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). <sect>Macro packages Using the <tt/.MACPACK/ directive, predefined macro packages may be included with just one command. Available macro packages are: <descrip> <tag><tt><idx>generic</idx></tt></tag> 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> <tag><tt><idx>longbranch</idx></tt></tag> 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> </descrip> <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 1998-2000 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>