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509 lines
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HTML
509 lines
18 KiB
HTML
<HTML>
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<HEAD>
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<TITLE>X-Assembler 2.0 Manual</TITLE>
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</HEAD>
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<BODY BACKGROUND="6502PROC.GIF">
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<CENTER>
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<H1>X-Assembler version 2.0</H1>
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coded by Fox/Taquart
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<HR>
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</CENTER>
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<H2>INTRODUCTION</H2>
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The X-Assembler is an assembler, which generates code for the 6502 processor.
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It is 99% compatible with Quick Assembler on 8-bit Atari.
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<BR>
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<H3>System requirements</H3>
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<UL>
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<LI> a PC compatible computer with 386 or better CPU
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<LI> a MS-DOS compatible OS
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<LI> a numeric coprocessor for generating sinus tables.
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Your CPU probably has a built-in coprocessor.
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</UL>
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<BR>
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<H3>Creating a source program</H3>
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Source file should be standard text file with IBM-style EOLs: CR/LF. You can
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use any text editor on PC to prepare your source code.
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Single line of source should not be longer than 256 characters.
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There is no limitation on the length of the file.
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Source may contain tabulators - there are treated as spaces.
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Assembler is NOT case-sensitive.
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<BR>
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<H3>Converting Quick Assembler files</H3>
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You must convert Atari text file into PC text file (EOL's from $9b to $0d/$0a),
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ATASCII 0-31 and 128-255 characters should be replaced with standard ASCII
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characters, using QAsm expressions.<BR>
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You also have to change all OPT directives, but usually you needn't them
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at all.
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<BR>
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<H3>Assembling a source program</H3>
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Syntax (parameters in brackets are optional):<BR>
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<PRE>XASM source [options]
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</PRE><TT>'source'</TT> is name of source file.
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If no extension given, the .ASX is added by default.<P>
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Options are:
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<DL>
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<DT><TT>/c</TT>
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<DD>Enable listing false conditionals.
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<DT><TT>/i</TT>
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<DD>Disable listing included source.
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<DT><TT>/l[:fname]</TT>
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<DD>Enable generating listing. If no <TT>fname</TT> given, listing is written to source.lst.
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<DT><TT>/o:fname</TT>
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<DD>Specify object name. Default is <TT>source.obx</TT>.
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<DT><TT>/s</TT>
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<DD>Disable converting spaces to tabs. Using tabs makes listing file shorter.<BR>
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Tab stops are assumed to be every 8 characters.
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<DT><TT>/t[:fname]</TT>
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<DD>List label table. If no fname given, table is written at the end of listing.
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</DL>
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If source is incorrect, X-Asm displays ONLY FIRST encountered error.<P>
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Errorlevels returned by X-Asm:<BR>
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3 = bad parameters, assembling not started<BR>
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2 = error occured<BR>
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1 = warning(s) only<BR>
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0 = no errors, no warnings<BR>
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<H3>Listing structure</H3>
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Line of listing includes:
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<UL>
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<LI> decimal number of line of source file (if source is different than in
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previous listed line, appropriate message line is generated)
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<LI> hexadecimal origin
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<LI> hexadecimal bytes written to object file
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Listed are also generated headers. A <TT>xxxx-yyyy></TT> in place of origin is
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a generated header: <TT>$xxxx</TT> is the first and <TT>$yyyy</TT> is the last byte of block.
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A <TT>FFFF></TT> represents two $ff bytes written as a header prefix.<P>
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A plus sign placed after hex numbers stands for more bytes written to object
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in this line, not listed through lack of space.
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<LI> remaining part of listing line is a copy of source
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</UL>
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<H3>Label table structure</H3>
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Line of label table includes:
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<UL>
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<LI> some info of label:<BR>
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<TT>n</TT> - label not used<BR>
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<TT>2</TT> - label value known in pass 2 only (label definition uses forward reference
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and thus you can't do forward references to that label)
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<LI> hex value of label
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<LI> name of label
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</UL>
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<HR>
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<H2>X-ASM LANGUAGE STRUCTURE</H2>
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Lines of source code may be:
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<UL>
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<LI> empty lines - ignored, of course
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<LI> comments - ignored, too
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<LI> statements - not ignored :-)
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</UL>
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Comment lines must have one of the following characters in the FIRST column
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of the line: <TT>* ; |</TT>
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<H3>Numbers</H3>
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Numbers are 32-bit signed integers, in the range of -$7fffffff..$7fffffff.
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A number can be:
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<UL>
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<LI> a decimal number <TT>-12345</TT>
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<LI> a hexadedecimal number <TT>$abcd</TT>
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<LI> a binary number <TT>%10100101</TT>
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<LI> a character <TT>'a'</TT> or <TT>"a"</TT> (new in 2.0!)
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<LI> a hardware register <TT>^31</TT>
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<LI> an origin counter <TT>*</TT>
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</UL>
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I think only 'a hardware register' should be explained. It is a short way
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of accessing Atari hardware registers:<P>
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<TT>^0x</TT> means <TT>$d00x</TT><BR>
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<TT>^1x</TT> means <TT>$d01x</TT><BR>
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<TT>^2x</TT> means <TT>$d20x</TT><BR>
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<TT>^3x</TT> means <TT>$d30x</TT><BR>
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<TT>^4x</TT> means <TT>$d40x</TT><BR>
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where x is a hexadecimal digit.
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<H3>Expressions</H3>
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Expressions are numbers combined with operators and brackets.
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You should use square brackets, because parentheses are reserved
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for 6502 indirect addressing. Currently there are 19 operators:<P>
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<TT>+ </TT>Addition<BR>
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<TT>- </TT>Subtraction<BR>
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<TT>* </TT>Multiplication<BR>
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<TT>/ </TT>Division<BR>
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<TT>% </TT>Remainder<BR>
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<TT>& </TT>Bitwise and<BR>
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<TT>| </TT>Bitwise or<BR>
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<TT>^ </TT>Bitwise xor<BR>
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<TT><< </TT>Arithmetic shift left<BR>
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<TT>>> </TT>Arithmetic shift right<BR>
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<TT>= </TT>Equal<BR>
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<TT><> </TT>Not equal<BR>
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<TT>!= </TT>Not equal (same as <>)<BR>
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<TT>< </TT>Less than<BR>
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<TT>> </TT>Greater than<BR>
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<TT><= </TT>Less or equal<BR>
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<TT>>= </TT>Greater or equal<BR>
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<TT>&& </TT>Logical and<BR>
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<TT>|| </TT>Logical or<P>
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Operator precedence:
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<PRE>
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first []
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* / % & << >>
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+ - | ^
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= <> != < > <= >=
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&&
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last ||
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</PRE>
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Compare and logical operators assume that zero is false and non-zero is true.
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They return -1 for true.<P>
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When calculating expression, 32-bit arithmetic is used. When range of 32 bits
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is exceeded, <TT>'Arithmetic overflow'</TT> error is generated.<P>
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If result of expression has improper size, <TT>'Value out of range'</TT> error occurs.<P>
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Note difference beetwen X-Asm 2.0 and QAsm/X-Asm 1.2: in older assemblers,
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which used 16-bit arithmetic, a <TT>LDA 0-1</TT> was correct (<TT>LDA $ffff</TT>), but X-Asm 2.0
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encounters an error: address can't be negative.<P>
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X-Asm recognizes now signed bytes: <TT>LDA #-1</TT> is OK.
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<H3>Statements</H3>
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A statement is divided into fields: a label field, an operation field,
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one or two operand fields, and a comment field. There should be at least
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one space between every two fields and there can't be any space within a field
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excluding strings.
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<H4>Label field</H4>
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This field is optional. It is required only by the <TT>EQU</TT> directive.
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Specyfying this field definies a label. Defined label represents an integer
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of range -$ffff..$ffff.<P>
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Name of label must begin in column 1 and can contain letters, digits
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and underscores (<TT>_</TT>). Digit can't be label's first character. Name of label
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can be as long as you want and all the characters are meaningful.<P>
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In Quick Assembler only 6 leading characters were recognized
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and some programs may not compile well under X-Asm for this reason.<P>
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Defining a label without using <TT>EQU</TT> makes it equal to current value
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of the origin counter. Label can't be redefined.
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<H4>Operation field</H4>
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Operation field is the only field which is always required.
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You have to put one or more spaces or tab characters between label
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and operation field. If no label is defined, line must start with a blank
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character. Operation field is always 3 letters long. It can be:
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<OL TYPE=a>
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<LI><I> a 6502 processor command</I>
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<LI><I> a compiler directive</I>
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<LI><I> a pseudo-command</I>
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</OL>
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<OL TYPE=a>
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<LI><I> 6502 command</I><BR>
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One of 56 well known processor commands.<BR><BR>
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<LI><I> compiler directive</I><BR>
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One of the following:
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<DL>
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<DT><TT><B>EQU</B></TT> - assign a value of expression to the label
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<DD>Note that label represents a number, not a text macro.<P>
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Examples:
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<PRE>five equ 5
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ten equ five+five
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</PRE>
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<DT><TT><B>OPT</B></TT> - set assembling options
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<DD>Currently there are two options: listing generating and headers generating.
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You can turn any of these on or off.<P>
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Examples:
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<PRE> opt l- listing off
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opt h- headers off
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opt l+h- listing on, headers off
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</PRE>
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Remember not to put a space between options:
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<PRE> opt l+ h-
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</PRE>
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is actually
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<PRE> opt l+
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</PRE>
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because h- is a comment.<P>
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Default (if no opt specified) is <TT>opt l+h+</TT>.<P>
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<DT><TT><B>ORG</B></TT> - set new origin counter
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<DD>Examples:
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<PRE> org $600 code will be located starting from $0600
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table org *+100 'table' points to 100 bytes of uninitialized data
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</PRE>
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New! You can set some options applied to new header (if headers are on):
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<PRE> org $600
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rts
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org a:$601
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</PRE>
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'a:' tells X-Asm to always make a header, even it is unnecessary (as in above).
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So by default X-Asm 2.0 does not generate unnecessary headers, distinct from
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QAsm and X-Asm 1.2.
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<PRE> org f:$700
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</PRE>
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'f:' works same as 'a:', but additionally tells to generate a $ff,$ff prefix
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before header. X-Asm adds it to the first header in file by default, so use
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this option only if you want the $ff's somewhere inside.<P>
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<DT><TT><B>DTA</B></TT> - define data
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<DD>You may define:
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<UL>
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<LI> numbers
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<UL>
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<LI> bytes: <TT>b(200)</TT>
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<LI> words: <TT>a(10000)</TT>
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<LI> low bytes of words: <TT>l(511)</TT> defines byte 255
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<LI> high bytes of words: <TT>h(511)</TT> defines byte 1
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You may enter many expressions in parentheses and combine different types
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of data in single line.<P>
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You may also define a sinus table. Enter this expression:<BR>
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<TT>sin(centre,amp,size,first,last)</TT><BR>
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where:
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<UL>
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<LI> centre is a number which is added to every value of sinus
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<LI> amp is the amplitude of sinus
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<LI> size is the period of sinus
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<LI> first,last define range of values in the table.
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They are optional. Default are 0,size-1.
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</UL>
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Example: <TT>dta a(sin(0,1000,256,0,63))</TT> defines table of 64 words representing
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a quarter of sinus with amplitude of 1000.
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<LI> real numbers: <TT>r(-1.23456e12)</TT><BR>
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Real numbers are written in 6-byte Atari Floating-Point format. You can't
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combine reals with operators, as you can integers.<P>
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</UL>
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<LI> text strings
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<UL>
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<LI> ASCII strings: <TT>c'Text'</TT> or <TT>c"Text"</TT>
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<LI> ANTIC strings: <TT>d'Text'</TT> or <TT>d"It's something new!"</TT>
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</UL>
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A character string consists of any of characters surrounded by quotation
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marks. Within a string, a single quotation mark character is
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represented by two succesive quotation marks.<P>
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Placing a '*' character after a string inverts bit 7 in every byte of string.<P>
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</UL>
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Examples of <TT>DTA</TT>:
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<PRE>
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dta b(2,5),a(1000,-1),l(12345,sin(0,127,256))
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dta d"ANTIC"*,c'It''s a string',b(155)
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</PRE>
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<DT><TT><B>ICL</B></TT> - include another source file
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<DD>Specifies another file to be included in the assembly as if the contests of
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the referenced file appeared in place of the <TT>ICL</TT> statement. The included file
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may contain other <TT>ICL</TT> statements.<P>
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Examples:
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<PRE>
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icl 'macros.asx'
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icl 'c:\atari\xasm\fileio.asx'
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</PRE>
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<DT><TT><B>END</B></TT> - end assembling of file
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<DD>Remaining part of the file is not assembled. If this statement does not occur,
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assembler stops assembling when encounters end of file.<BR>
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Example:
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<PRE>
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end
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</PRE>
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<DT><TT><B>INS</B></TT> - insert contents of file
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<DD>Copies every byte of specified file into object file and moves origin counter,
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as if these bytes were defined with <TT>DTA</TT>.<P>
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Examples:
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<PRE>
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ins 'picture.raw'
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ins 'tables.dat'
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</PRE>
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New! You may specify range of inserted file. Syntax is:
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<PRE>
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ins 'file'[,offset[,length]]
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</PRE>
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First byte in file has offset 0.<P>
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If offset is negative, it is counted from the end of file.
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<PRE>
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ins 'file',-256 inserts last 256 bytes of file
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ins 'file',10,10 inserts bytes 10..19 of file
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</PRE>
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<DT><TT><B>RUN</B></TT> - generate run address
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<DD>The Atari executable program should have run address specified. Remember that
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a program may be loaded in many areas of memory and started from any address.
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<PRE> run addr
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</PRE>
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is equivalent to:
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<PRE> org $2e0
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dta a(addr)
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</PRE>
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Examples:
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<PRE> run start
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run program
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</PRE>
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<DT><TT><B>INI</B></TT> - generate init address
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<DD>The Atari executable program may have some routines which are executed during
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loading process. There may be many init blocks in one file.
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Examples:
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<PRE> ini init
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ini showpic
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</PRE>
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<DT><TT><B>ERT</B></TT> - generate error if expression is true
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<DD>Examples:
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<PRE> ert *>$c000
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ert len1>$ff||len2>$ff
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</PRE>
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<DT><TT><B>IFT</B></TT> - assemble if expression is true<BR>
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<TT><B>ELS</B></TT> - else<BR>
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<TT><B>EIF</B></TT> - end if<BR>
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<DD>Example:
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<PRE>noscr equ 1
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ift noscr
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lda #0
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els
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lda #$22
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eif
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sta $22f
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</PRE>
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</DL>
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<LI><I> pseudo-command</I><BR>
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It is something like built-in macro. It replaces two or more standard
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processor commands. Note that it is not an illegal instruction and works
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on typical 6502.
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<DL>
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<DT><TT><B>ADD</B></TT> - addition without carry
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<DD>If you ever programmed 6502, you must have noticed that you had to use a <TT>CLC</TT>
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before <TT>ADC</TT> for every simple addition.<BR>
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X-Asm can do it for you. <TT>ADD</TT> simply replaces two instructions: <TT>CLC</TT> and <TT>ADC</TT>.<P>
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<DT><TT><B>SUB</B></TT> - subtraction
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<DD>It is <TT>SEC</TT> and <TT>SBC</TT>.<P>
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<DT><TT><B>JNE, JEQ, JCC, JCS, JPL, JMI, JVC, JVS</B></TT> - conditional jumps
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<DD>They are a kind of 'long' branches. While standard branches (<TT>BNE, BEQ</TT>) have
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range of -128..+127, these jumps have range of all 64 kB.<P>
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For example: a <TT>JNE DEST</TT> is replaced with:
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<PRE> beq *+5
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jmp dest
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</PRE>
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<DT><TT><B>INW</B></TT> - increment word
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<DD>It is a 16-bit memory increment command. An <TT>INW DEST</TT> will be replaced by:
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<PRE> inc dest
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bne _skip
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inc dest+1
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_skip equ *
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</PRE>
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The <TT>_skip</TT> label is not declared of course.<P>
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<DT><TT><B>MVA, MVX, MVY</B></TT> - move byte using accumulator, X or Y
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<DD>These pseudo-commands require two operands.
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<PRE> mva source dest = lda source : sta dest
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mvx source dest = ldx source : stx dest
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mvy source dest = ldy source : sty dest
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</PRE>
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<DT><TT><B>MWA, MWX, MWY</B></TT> - move word using accumulator, X or Y
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<DD>Also require two operands. They are something like combination of two <TT>MV*</TT>'s:
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one to move low byte, and the other to move high byte.<P>
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You can't use indirect nor pseudo addressing modes with <TT>MW*</TT>.<P>
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Destination must be absolute address (indexed or not).<P>
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When source is also absolute, a <TT>MW* SOURCE DEST</TT> will be:
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<PRE> mv* source dest
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mv* source+1 dest+1
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</PRE>
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When source is immediate, a <TT>MW* #IMMED</TT> dest will be
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<PRE> mv* <immed dest
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mv* >immed dest+1
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</PRE>
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but when <IMMED = >IMMED and IMMED is not forward-referenced,
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X-Asm uses optimization:
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<PRE> mv* <immed dest
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st* dest+1
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</PRE>
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</DL>
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</OL>
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<H4>Operand</H4>
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It depends on the operation field. Some statements don't need an operand
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or need two operands.<P>
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6502 commands require operand depending on the addressing mode.
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Addressing modes should be entered in standard convention except
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the accumulator addressing mode, which should be marked with a <TT>@</TT> character
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(as in Quick Assembler).<P>
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There are two extra immediate addressing modes: < and >, which use low/high
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byte of word is used rather than byte value.<P>
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In absolute addressing modes, X-Asm examines expression and uses zero-page
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addressing mode if it thinks it is possible to do it. You may override it
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with <TT>a:</TT> and <TT>z:</TT> prefixes.<P>
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Examples:
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<PRE>
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nop
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asl @
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lda >$1234 assembles to lda #$12
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|
lda $100,x
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lda a:0 generates 16-bit address
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jmp ($0a)
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lda ($80),y
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</PRE>
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|
|
|
New! X-Asm 2.0 brings pseudo addressing modes. They are similar to
|
|
pseudo-commands and you may use them as standard addressing modes
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in all 6502 commands and pseudo-commands, excluding <TT>MW*</TT>:
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<PRE> cmd a,x+ = cmd a,x : inx
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|
cmd a,x- = cmd a,x : dex
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|
cmd a,y+ = cmd a,y : iny
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cmd a,y- = cmd a,y : dey
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|
cmd (z),y+ = cmd (z),y : iny
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|
cmd (z),y- = cmd (z),y : dey
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|
cmd (z,0) = ldx #0 : cmd (z,x)
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|
cmd (z),0 = ldy #0 : cmd (z),y
|
|
</PRE>
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|
<H3>Problems</H3>
|
|
These notes may help you solve problems:
|
|
<UL>
|
|
<LI> No spaces are allowed within a field.
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|
<PRE>label equ 1 + 2
|
|
</PRE>
|
|
causes label to be equal 1 (<TT>+ 2</TT> is treated as a comment).<P>
|
|
|
|
<LI> <TT><</TT> and <TT>></TT> represent addressing modes rather than LOW and HIGH operators.<P>
|
|
You specify <TT>lda <table</TT>, not <TT>lda #<table</TT> like in most 6502 assemblers.<P>
|
|
|
|
<LI> Label definition does not include a colon
|
|
<PRE>label: lda ^4b ERROR - colon after label name
|
|
</PRE>
|
|
|
|
<LI> Exactly one run address should be specified<P>
|
|
Remember that unlike in other assemblers
|
|
<PRE> end start
|
|
</PRE>
|
|
does not tell the assembler that <TT>start</TT> is the run address (it is a comment).
|
|
You must specify the run address with <TT>RUN</TT> directive.<P>
|
|
|
|
<LI> X-Asm reads source twice (in pass 1 and pass 2)<BR>
|
|
This allows forward references, but not too complex.<P>
|
|
Keep in mind that assembler should know all the values in second pass.<P>
|
|
Example:
|
|
<PRE>two equ one+one This value is known in 2nd pass only
|
|
one equ 1 This value is known as early as in 1st pass
|
|
</PRE>
|
|
These values can be fixed in 2 passes.<P>
|
|
But if you insert following statement as first line:
|
|
<PRE>three equ one+two
|
|
</PRE>
|
|
X-Asm will generate an error because it doesn't know the value of <TT>three</TT> in
|
|
second pass.<BR>
|
|
(sorry for v1.2 users: <TT>EQU</TT> forward reference didn't work at all).<P>
|
|
|
|
<LI> X-Asm displays only first error<BR>
|
|
When you correct one error don't be surpised if you get another one.<P>
|
|
|
|
<LI> If you encounter X-Asm works improperly, please <A HREF=mailto:pfusik@elka.pw.edu.pl>let me know</A>.
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|
</UL>
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