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714 lines
25 KiB
HTML
<HTML>
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<HEAD>
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<TITLE>X-Assembler 2.2 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 2.2</H1>
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by <A HREF="mailto:pfusik@elka.pw.edu.pl">Fox/Taquart</A><P>
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</CENTER>
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<HR></P><A NAME="intro">
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<H2>INTRODUCTION
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<A HREF="#usage">USAGE</A>
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<A HREF="#syntax">SYNTAX</A>
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<A HREF="#faq">FAQ</A>
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<A HREF="index.htm">BACK</A>
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</H2>
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The X-Assembler is an cross-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>CHANGES</H3>
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<H4>Version 2.2</H4>
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<UL>
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<LI> invalid absolute <TT>CPX</TT> and <TT>CPY</TT> op-codes bug fixed
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<LI> branch addressing mode not checking bug fixed
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<LI> <TT>ICL</TT> in last line bug fixed
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<LI> <TT>OPT H-H+</TT> bug fixed
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<LI> first <TT>ORG *</TT> bug fixed
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<LI> origin setting not required until not used
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<LI> Unix ($0a), Macintosh ($0d) and Atari ($9b) EOLs allowed in source
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<LI> value of 'true' changed to 1
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<LI> <A HREF="#new_environment">
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setting environment variables on error option</A>
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<LI> <A HREF="#new_newer">
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assembling only if source newer than object option</A>
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<LI> <A HREF="#new_opcode">op-code extracting</A>
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<LI> <A HREF="#new_linerep">line repeating</A>
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<LI> <A HREF="#new_pairing">instructions pairing</A>
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<LI> <A HREF="#new_repskip">conditional repeat and skip pseudo commands</A>
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<LI> <A HREF="#new_adrmodes">
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<TT>(),0+</TT> and <TT>(),0-</TT> pseudo addressing modes</A>
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</UL>
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<H4>Version 2.0</H4>
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<UL>
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<LI> truncating name of object bug fixed
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<LI> <TT>EQU</TT> and <TT>DTA</TT> forward reference bugs fixed
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<LI> hex number recognizing bug fixed
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<LI> now <TT>.OBX</TT> is default extension for Atari executables
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<LI> assembling options (switches and <TT>OPT</TT> directive)
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<LI> listing generation
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<LI> label table generation
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<LI> conditional assembling
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<LI> user errors
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<LI> warnings
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<LI> improved headers generation
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<LI> improved expressions - 19 operators and brackets, 32-bit arithmetic
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<LI> improved signed numbers
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<LI> 6 new pseudo commands (memory-to-memory move)
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<LI> 8 pseudo addressing modes
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<LI> indirect conditional jumps
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<LI> Atari floating-point numbers generation
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<LI> improved <TT>INS</TT>: inserting specified part of file
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</UL>
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<H4>Version 1.2</H4>
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<UL>
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<LI> first release
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</UL>
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<HR></P><A NAME="usage">
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<H2><A HREF="#intro">INTRODUCTION</A>
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USAGE
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<A HREF="#syntax">SYNTAX</A>
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<A HREF="#faq">FAQ</A>
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<A HREF="index.htm">BACK</A>
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</H2>
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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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<H3>Creating a source program</H3>
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Source file should be plain ASCII file. Although different EOLs are supported,
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you would probably prefer CR/LF EOLs because of text editor.<BR>
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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.<BR>
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Source may contain tabulators, which are treated as spaces.<BR>
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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 <TT>OPT</TT> directives,
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but usually you needn't them at all.
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<BR>
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<H3>Assembling a source program</H3>
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You run assembler from DOS prompt with following syntax:<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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Optional options are:
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<DL>
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<DT><TT>/c</TT>
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<DD>Enable listing false conditionals.<BR>
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By default lines skipped because of false condition are not listed.<P>
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<A NAME="new_environment">
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<DT><TT>/e</TT>
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<DD>Enable setting environment variables when error occurs.<BR>
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With this option, X-Asm sets two environment variables: ERRFILE and ERRLINE.
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They may be used in a batch file to locate error and set editor on it.
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For example, in my batch file I use such construction:
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<PRE>XASM %1 /e
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IF NOT ERRORLEVEL 1 GOTO ok
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NCE +%ERRLINE% %ERRFILE%
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</PRE>
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NCE stands for Norton Classic Editor.<P>
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If there was no error, variables point at last warning.
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If no warning occured, they are removed from the environment.<P>
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<DT><TT>/i</TT>
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<DD>Disable listing included source.<BR>
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Only main source file will be listed.<P>
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<DT><TT>/l[:fname]</TT>
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<DD>Enable generating listing.
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If no <TT>fname</TT> given, listing is written to <TT>source.lst.</TT><P>
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<A NAME="new_newer">
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<DT><TT>/n</TT>
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<DD>Check source and object modification times and assemble only
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if source is newer than object file. X-Asm does NOT check included
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nor inserted files but only main source, so be careful with this option.<P>
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<DT><TT>/o:fname</TT>
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<DD>Specify object name. Default is <TT>source.obx</TT>.<P>
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<DT><TT>/s</TT>
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<DD>Disable converting spaces to tabs in listing.
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Using tabs makes listing file shorter.<BR>
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Tab stops are assumed to be every 8 characters.<P>
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<DT><TT>/t[:fname]</TT>
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<DD>List label table.
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If no <TT>fname</TT> given, table is written at the end of listing.<P>
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</DL>
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If source is incorrect, X-Asm stops on 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<BR>
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Listed are also generated headers. A <TT>xxxx-yyyy></TT> in place of origin
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represents generated header: <TT>$xxxx</TT> is the first and <TT>$yyyy</TT>
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is the last byte of the block.
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A <TT>FFFF></TT> represents two $ff bytes written as a header prefix.<BR>
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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 line
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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 label attributes:<BR>
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<TT>n</TT> - label defined but not used elsewhere<BR>
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<TT>2</TT> - label value known in pass 2 only (label definition uses forward
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reference and thus you can't do forward references to that label)
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<LI> hexadecimal value of the label
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<LI> name of the label
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</UL>
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<HR></P><A NAME="syntax">
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<H2><A HREF="#intro">INTRODUCTION</A>
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<A HREF="#usage">USAGE</A>
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SYNTAX
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<A HREF="#faq">FAQ</A>
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<A HREF="index.htm">BACK</A>
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</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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</P><A NAME="expressions">
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<H3>Expressions <A HREF="#statements">Statements</A></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.
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<H4>Numbers</H4>
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Numbers are 32-bit signed integers, in the range of -$7fffffff..$7fffffff.
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A number can be:
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<TABLE>
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<TR><TD WIDTH=300><UL><LI> a decimal number</TD><TD><TT>-12345</TT></TD></TR>
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<TR><TD><UL><LI> a hexadedecimal number</TD><TD><TT>$abcd</TT></TD></TR>
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<TR><TD><UL><LI> a binary number</TD><TD><TT>%10100101</TT></TD></TR>
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<TR><TD><UL><LI> an ASCII character</TD><TD><TT>'a'</TT> or <TT>"a"</TT></TD></TR>
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<TR><TD><UL><LI> an origin counter</TD><TD><TT>*</TT></TD></TR>
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<TR><TD><UL><LI> a hardware register</TD><TD><TT>^31</TT></TD></TR>
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</UL></TABLE>
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<DIV STYLE="MARGIN-LEFT: 54">
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An abbreviation of Atari hardware register:<BR>
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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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</DIV>
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<A NAME="new_opcode">
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<TABLE>
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<TR><TD WIDTH=300><UL><LI> an op-code</TD><TD><TT>{lda #0}</TT></TD></TR>
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</UL></TABLE>
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<DIV STYLE="MARGIN-LEFT: 54">
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Byte op-code of instruction inside braces. Operand is discarded
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and is necessary only for identifying addressing mode.
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Instruction should begin right after left brace and right brace should
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immediately follow the operand or the command in implied addressing mode.
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</DIV>
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<P>
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<H4>Operators</H4>
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Currently there are 19 operators:<P>
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<TABLE>
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<TR><TD><TT>+ </TT></TD><TD>Addition</TD></TR>
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<TR><TD><TT>- </TT></TD><TD>Subtraction</TD></TR>
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<TR><TD><TT>* </TT></TD><TD>Multiplication</TD></TR>
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<TR><TD><TT>/ </TT></TD><TD>Division</TD></TR>
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<TR><TD><TT>% </TT></TD><TD>Remainder</TD></TR>
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<TR><TD><TT>& </TT></TD><TD>Bitwise and</TD></TR>
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<TR><TD><TT>| </TT></TD><TD>Bitwise or</TD></TR>
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<TR><TD><TT>^ </TT></TD><TD>Bitwise xor</TD></TR>
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<TR><TD><TT><< </TT></TD><TD>Arithmetic shift left</TD></TR>
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<TR><TD><TT>>> </TT></TD><TD>Arithmetic shift right</TD></TR>
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<TR><TD><TT>= </TT></TD><TD>Equal</TD></TR>
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<TR><TD><TT><> </TT></TD><TD>Not equal</TD></TR>
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<TR><TD><TT>!= </TT></TD><TD>Not equal (same as <TT><></TT>)</TD></TR>
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<TR><TD><TT>< </TT></TD><TD>Less than</TD></TR>
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<TR><TD><TT>> </TT></TD><TD>Greater than</TD></TR>
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<TR><TD><TT><= </TT></TD><TD>Less or equal</TD></TR>
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<TR><TD><TT>>= </TT></TD><TD>Greater or equal</TD></TR>
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<TR><TD><TT>&& </TT></TD><TD>Logical and</TD></TR>
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<TR><TD><TT>|| </TT></TD><TD>Logical or</TD></TR>
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</TABLE>
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<P>
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Operator precedence:
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<TABLE>
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<TR><TD>first</TD><TD><TT>[]</TT></TD></TR>
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<TR><TD> </TD><TD><TT>* / % & << >></TT></TD></TR>
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<TR><TD> </TD><TD><TT>+ - | ^</TT></TD></TR>
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<TR><TD> </TD><TD><TT>= <> != < > <= >=</TT></TD></TR>
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<TR><TD> </TD><TD><TT>&&</TT></TD></TR>
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<TR><TD>last </TD><TD><TT>||</TT></TD></TR>
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</TABLE>
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<P>
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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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</P><A NAME="statements">
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<H3><A HREF="#expressions">Expressions</A> Statements</H3>
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A statement is divided into fields:
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<UL>
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<LI> <A HREF="#label">label field</A>
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<LI> <A HREF="#operation">operation field</A>
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<LI> <A HREF="#operand">one or two operand fields</A>
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<LI> <A HREF="#comment">comment field</A>
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</UL>
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There should be at least one space between every two fields
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and there can't be any space within a field excluding strings.
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</P><A NAME="label"><H4>Label field</H4>
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This field is optional. It starts from first character of line, without
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any blank characters before. It has two applications:
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<UL>
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<LI> Defining a label.<BR>
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Label is a symbol representing an integer of range -$ffff..$ffff.<BR>
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Name of a label can contain letters, digits and underscores (<TT>_</TT>).
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Digit can't be label's first character.
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Name of a label can be as long as you want and all the characters
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are meaningful. In Quick Assembler only 6 leading characters were recognized
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and some programs may not compile under X-Asm for this reason.<BR>
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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.<BR>
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Label can't be redefined.<P>
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<A NAME="new_linerep">
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<LI> Repeating the line.<BR>
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Repeating means assembling single line several times as if
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there were several identical lines. Note it is not just duplicating
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bytes written to object.<BR>
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Repeat count, which can be any valid expression, has to be preceded
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with a colon.<BR>
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Examples:
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<PRE>:4 asl @
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:2 dta a(*)
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</PRE>
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In the latter example each <TT>DTA</TT> has different operand value.<BR>
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If repeat count equals zero, remaining part of line is not assembled.
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This allows conditional assembly on single line to be more compact.
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</UL>
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You can not define a label in line which you repeat.<P>
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<A NAME="new_pairing">
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</P><A NAME="operation"><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 consists of one or two instructions.
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The latter case is called instructions pairing, because a pair
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of instructions have shared operand. You separate instructions
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with a colon.<BR>
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Example:
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<PRE> adc:sta $80
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</PRE>is equivalent to
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<PRE> adc $80
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sta $80
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</PRE>
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Single instruction always consists of 3 letters. It can be:
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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:<P>
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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.<BR>
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Examples:
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<PRE>five equ 5
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here equ *
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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.<BR>
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Default (if no <TT>OPT</TT> specified) is <TT>opt l+h+</TT>.<BR>
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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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<DT><TT><B>ORG</B></TT> - set new origin counter
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<DD>You can set some options applied to new header (if headers are on):
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<UL>
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<LI><TT>a:</TT> tells X-Asm to always make a header, even it is unnecessary,
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like in <TT>ORG *</TT>.
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<LI><TT>f:</TT> works same as <TT>a:</TT>, but additionally tells to generate
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a $ff,$ff prefix before header. X-Asm adds it to the first header in file
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by default, so use this option only if you want the $ff's somewhere inside.<BR>
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</UL>
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Examples:
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<PRE> org $600
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org f:$700
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table org *+100
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</PRE>
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In the latter example <TT>table</TT> points to 100 bytes
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of uninitialized data (note label is assigned to <TT>*</TT>
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before <TT>ORG</TT> directive is executed).<P>
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<DT><TT><B>DTA</B></TT> - define data
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<DD>There are various data types:
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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<BR>
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You may enter many expressions in parentheses and combine different types
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of data in single line, separating things with commas.<BR>
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You may also define a sinus table. Syntax is:<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> <TT>centre</TT> is a number which is added to every sinus value
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<LI> <TT>amp</TT> is the amplitude of sinus
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<LI> <TT>size</TT> is the period of sinus
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<LI> <TT>first,last</TT> define range of values in the table.
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They are optional. Default are <TT>0,size-1</TT>.
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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
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representing a quarter of sinus with amplitude of 1000.<P>
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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"Text"</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.<BR>
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Placing a <TT>*</TT> character after a string inverts
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high bit 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)
|
|
</PRE>
|
|
|
|
<DT><TT><B>ICL</B></TT> - include another source file
|
|
<DD>Specifies another file to be included in the assembly as if the contests of
|
|
the referenced file appeared in place of the <TT>ICL</TT> statement.
|
|
The included file may contain other <TT>ICL</TT> statements.
|
|
The <TT>.ASX</TT> extension is added if none given.<P>
|
|
Examples:
|
|
<PRE>
|
|
icl 'macros.asx'
|
|
icl 'c:\atari\xasm\fileio'
|
|
</PRE>
|
|
|
|
<DT><TT><B>END</B></TT> - end assembling file
|
|
<DD>Remaining part of the file is not assembled. If this statement does
|
|
not occur, assembler stops assembling when encounters end of file.<BR>
|
|
Example:
|
|
<PRE>
|
|
end
|
|
</PRE>
|
|
|
|
<DT><TT><B>INS</B></TT> - insert contents of file
|
|
<DD>Copies every byte of specified file into object file and moves origin
|
|
counter, as if these bytes were defined with <TT>DTA</TT>.<BR>
|
|
You may specify range of inserted file. Syntax is:
|
|
<PRE>
|
|
ins 'file'[,offset[,length]]
|
|
</PRE>
|
|
First byte in file has offset 0.<BR>
|
|
If offset is negative, it is counted from the end of file.<BR>
|
|
Examples:
|
|
<PRE>
|
|
ins 'picture.raw'
|
|
ins 'file',-256 insert last 256 bytes of file
|
|
ins 'file',10,10 insert bytes 10..19 of file
|
|
</PRE>
|
|
|
|
<DT><TT><B>RUN</B></TT> - generate run address
|
|
<DD>The Atari executable program should have run address specified.
|
|
A program may be loaded in many areas of memory and started from any address.
|
|
<PRE> run addr
|
|
</PRE>
|
|
is equivalent to:
|
|
<PRE> org $2e0
|
|
dta a(addr)
|
|
</PRE>
|
|
Examples:
|
|
<PRE> run start
|
|
run program
|
|
</PRE>
|
|
|
|
<DT><TT><B>INI</B></TT> - generate init address
|
|
<DD>The Atari executable program may have some routines which are executed
|
|
during loading process. There may be many init blocks in one file.<BR>
|
|
Examples:
|
|
<PRE> ini init
|
|
ini showpic
|
|
</PRE>
|
|
|
|
<DT><TT><B>ERT</B></TT> - generate error if expression is true
|
|
<DD>Examples:
|
|
<PRE> ert *>$c000
|
|
ert len1>$ff||len2>$ff
|
|
</PRE>
|
|
|
|
<DT><TT><B>IFT</B></TT> - assemble if expression is true<BR>
|
|
<TT><B>ELS</B></TT> - else<BR>
|
|
<TT><B>EIF</B></TT> - end if<BR>
|
|
<DD>With these directives you can construct fragments which
|
|
are assembled when a condition is met.
|
|
Conditional constructions can be nested.<BR>
|
|
Example:
|
|
<PRE>noscr equ 1
|
|
ift noscr
|
|
lda #0
|
|
els
|
|
lda #$22
|
|
eif
|
|
sta $22f
|
|
</PRE>
|
|
Above example can be rewritten using line repeating feature:
|
|
<PRE>noscr equ 1
|
|
:noscr<>0 lda #0
|
|
:noscr=0 lda #$22
|
|
sta $22f
|
|
</PRE>
|
|
|
|
</DL>
|
|
<LI><I> pseudo-command</I><BR>
|
|
It is something like built-in macro.
|
|
Note that it is not an illegal instruction and works on typical 6502.<P>
|
|
<DL>
|
|
<DT><TT><B>ADD</B></TT> - addition without carry
|
|
<DD>If you ever programmed 6502, you must have noticed that you had
|
|
to use a <TT>CLC</TT> before <TT>ADC</TT> for every simple addition.<BR>
|
|
X-Asm can do it for you. <TT>ADD</TT> replaces two instructions:
|
|
<TT>CLC</TT> and <TT>ADC</TT>.<P>
|
|
|
|
<DT><TT><B>SUB</B></TT> - subtraction
|
|
<DD>It is <TT>SEC</TT> and <TT>SBC</TT>.<P>
|
|
|
|
<A NAME="new_repskip">
|
|
<DT><TT><B>RCC, RCS, REQ, RMI, RNE, RPL, RVC, RVS</B></TT> - conditional repeat
|
|
<DD>They are branches to the previous instruction.
|
|
They take no operand, because the branch target
|
|
is the address of previously assembled instruction.<BR>
|
|
Example:
|
|
<PRE> ldx #0
|
|
mva:rne $500,x $600,x+
|
|
</PRE>
|
|
The example code copies memory $500-$5ff to $600-$6ff.
|
|
With standard 6502 commands only it would be:
|
|
<PRE> ldx #0
|
|
loop lda $500,x
|
|
sta $600,x
|
|
inx
|
|
bne loop
|
|
</PRE>
|
|
|
|
<DT><TT><B>SCC, SCS, SEQ, SMI, SNE, SPL, SVC, SVS</B></TT> - conditional skip
|
|
<DD>They are branches over the next instructions. No operand is required,
|
|
because the target is the address of instruction following
|
|
the next instruction.<BR>
|
|
Example:
|
|
<PRE> lda #40
|
|
add:sta $80
|
|
scc:inc $81
|
|
</PRE>
|
|
In the above example word variable $80 is incremented by 40.<BR>
|
|
Nor conditional repeat nor skip pseudo-commands require operand,
|
|
thus they can be paired with any other command.<P>
|
|
|
|
<DT><TT><B>JCC, JCS, JEQ, JMI, JNE, JPL, JVC, JVS</B></TT> - conditional jumps
|
|
<DD>They are a kind of 'long' branches. While standard branches
|
|
(<TT>BNE, BEQ</TT>) have range of -128..+127, these jumps have range
|
|
of all 64 kB.<BR>
|
|
Example:
|
|
<PRE> jne dest
|
|
</PRE>is equivalent to:
|
|
<PRE> seq:jmp dest
|
|
</PRE>
|
|
|
|
<DT><TT><B>INW</B></TT> - increment word
|
|
<DD>It is a 16-bit memory increment command.<BR>
|
|
Example:
|
|
<PRE> inw dest
|
|
</PRE>is equivalent to:
|
|
<PRE> inc dest
|
|
sne:inc dest+1
|
|
</PRE>
|
|
|
|
<DT><TT><B>MVA, MVX, MVY</B></TT> - move byte using accumulator, X or Y
|
|
<DD>Any of these pseudo-commands requires two operands
|
|
and substitutes two commands:
|
|
<PRE> mva source dest = lda source : sta dest
|
|
mvx source dest = ldx source : stx dest
|
|
mvy source dest = ldy source : sty dest
|
|
</PRE>
|
|
|
|
<DT><TT><B>MWA, MWX, MWY</B></TT> - move word using accumulator, X or Y
|
|
<DD>They also require two operands
|
|
and are combinations of two <TT>MV*</TT>'s:
|
|
one to move low byte, and the other to move high byte.<BR>
|
|
You can't use indirect nor pseudo addressing modes with <TT>MW*</TT>.
|
|
Destination must be absolute address (indexed or not).<BR>
|
|
When source is also absolute, a <TT>MW* SOURCE DEST</TT> will be:
|
|
<PRE> mv* source dest
|
|
mv* source+1 dest+1
|
|
</PRE>
|
|
When source is immediate, a <TT>MW* #IMMED DEST</TT> will be:
|
|
<PRE> mv* <immed dest
|
|
mv* >immed dest+1
|
|
</PRE>
|
|
When <TT><immed</TT> equals <TT>>immed</TT> and <TT>immed</TT>
|
|
is not forward-referenced, X-Asm uses optimization:
|
|
<PRE> mv* <immed dest
|
|
st* dest+1
|
|
</PRE>
|
|
</DL>
|
|
</OL>
|
|
|
|
</P><A NAME="operand"><H4>Operand</H4>
|
|
It depends on the operation field. Some statements don't need any operand,
|
|
other need two operands.<P>
|
|
|
|
6502 commands require operand depending on the addressing mode.
|
|
Addressing modes should be entered in standard convention except
|
|
the accumulator addressing mode, which should be marked with a
|
|
<TT>@</TT> character (as in Quick Assembler).<P>
|
|
|
|
There are two extra immediate addressing modes:
|
|
<TT><</TT> and <TT>></TT>,
|
|
which use low/high byte of word rather than byte value.<P>
|
|
|
|
In absolute addressing modes, X-Asm examines expression and uses zero-page
|
|
addressing mode if it thinks it is possible to do it. You may override it
|
|
with <TT>a:</TT> and <TT>z:</TT> prefixes.<P>
|
|
|
|
Examples:
|
|
<PRE>
|
|
nop
|
|
asl @
|
|
lda >$1234 assembles to lda #$12
|
|
lda $100,x
|
|
lda a:0 generates 16-bit address
|
|
jmp ($0a)
|
|
lda ($80),y
|
|
</PRE>
|
|
|
|
There are also pseudo addressing modes, which are similar to
|
|
pseudo-commands. You may use them as standard addressing modes
|
|
in all 6502 commands and pseudo-commands excluding
|
|
<TT>MWA</TT>, <TT>MWX</TT> and <TT>MWY</TT> only:
|
|
<PRE> cmd a,x+ = cmd a,x : inx
|
|
cmd a,x- = cmd a,x : dex
|
|
cmd a,y+ = cmd a,y : iny
|
|
cmd a,y- = cmd a,y : dey
|
|
cmd (z),y+ = cmd (z),y : iny
|
|
cmd (z),y- = cmd (z),y : dey
|
|
cmd (z,0) = ldx #0 : cmd (z,x)
|
|
cmd (z),0 = ldy #0 : cmd (z),y
|
|
<A NAME="new_adrmodes"> cmd (z),0+ = ldy #0 : cmd (z),y : iny
|
|
cmd (z),0- = ldy #0 : cmd (z),y : dey
|
|
</PRE>
|
|
|
|
</P><A NAME="comment"><H4>Comment</H4>
|
|
Comment in a statement does not start from any special character
|
|
like <TT>;</TT> for example. Comment field is implied when appropriate
|
|
number of operands was taken.<P>
|
|
|
|
<HR></P><A NAME="faq">
|
|
<H2><A HREF="#intro">INTRODUCTION</A>
|
|
<A HREF="#usage">USAGE</A>
|
|
<A HREF="#syntax">SYNTAX</A>
|
|
FAQ
|
|
<A HREF="index.htm">BACK</A>
|
|
</H2>
|
|
<UL>
|
|
<LI><B>Q:</B> Why does X-Asm ignore <TT>+2</TT> in following line?
|
|
<PRE>label equ 1 +2
|
|
</PRE>
|
|
<B>A:</B> X-Asm treats space as operand terminator. Remaining part of line
|
|
is a comment. You should write <TT>1+2</TT> without any spaces.<P>
|
|
|
|
<LI><B>Q:</B> Why does <TT>lda #<table</TT> not work?<P>
|
|
<B>A:</B> <TT><</TT> and <TT>></TT> represent addressing modes
|
|
rather than LOW and HIGH operators.<BR>
|
|
You specify <TT>lda <table</TT>, not <TT>lda #<table</TT>
|
|
like in most 6502 assemblers.<P>
|
|
|
|
<LI><B>Q:</B> What's wrong with <TT>asl a</TT> ?<P>
|
|
<B>A:</B> You should use <TT>@</TT> for accumulator addressing mode.<P>
|
|
|
|
<LI><B>Q:</B> What's wrong in following line?
|
|
<PRE>label: lda #0
|
|
</PRE>
|
|
<B>A:</B> Label definition can not include a colon.<P>
|
|
|
|
<LI><B>Q:</B> I wrote <TT>end start</TT>, where <TT>start</TT> points
|
|
to program beginning, but program seems not to start there. Why?<P>
|
|
<B>A:</B> You should have explicit run address specified.
|
|
Use <TT>run start</TT> directive. <TT>end</TT> takes no operand.<P>
|
|
|
|
<LI><B>Q:</B> Why this construction does not work:
|
|
<PRE>three equ one+two
|
|
two equ one+one
|
|
one equ 1
|
|
</PRE>
|
|
while this does:
|
|
<PRE>
|
|
two equ one+one
|
|
one equ 1
|
|
</PRE>
|
|
<B>A:</B> X-Asm reads source twice (in pass 1 and pass 2)
|
|
from the beginning until the end.<BR>
|
|
This allows forward references, but not too complex.<BR>
|
|
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 two passes.<BR>
|
|
If you insert following statement as first line:
|
|
<PRE>three equ one+two
|
|
</PRE>
|
|
X-Asm will generate an error because it can't fix
|
|
the value of <TT>three</TT> in second pass.<P>
|
|
|
|
<LI><B>Q:</B> X-Asm displayed single error while assembling my program.
|
|
When I fixed it, another error appeared. Why?<P>
|
|
<B>A:</B> X-Asm displays only first error.<BR>
|
|
When you were assembling for the first time, both errors might exist,
|
|
but X-Asm stopped assembling on the first one.<P>
|
|
|
|
<LI> If you have other questions/problems,
|
|
<A HREF=mailto:pfusik@elka.pw.edu.pl>write to me</A>.
|
|
</UL>
|
|
</BODY>
|
|
</HTML> |