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diff docs/manual/x543.html @ 333:507f442dc71e
Add support for 6800 compatibility instructions.
The occasional program uses the 6800 compatibility instructions since they
are actually specified by Motorola in at least some documentation. They
advertised the 6809 as source compatible with the 6800.
This mode is not enabled by default, however. It is my belief that receiving
an error when using a non-6809 instruction is more useful since it is
unlikely that much 6800 source code is being assembled for the 6809 these
days. Nevertheless, the --6809compat option is present for just those
purposes so one does not have to resort to using macros (which would work
equally well in most cases).
| author | William Astle <lost@l-w.ca> |
|---|---|
| date | Tue, 15 Apr 2014 10:57:34 -0600 |
| parents | |
| children |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/docs/manual/x543.html Tue Apr 15 10:57:34 2014 -0600 @@ -0,0 +1,228 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> +<HTML +><HEAD +><TITLE +>Structures</TITLE +><META +NAME="GENERATOR" +CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK +REL="HOME" +TITLE="LW Tool Chain" +HREF="index.html"><LINK +REL="UP" +TITLE="LWASM" +HREF="c62.html"><LINK +REL="PREVIOUS" +TITLE="Macros" +HREF="x520.html"><LINK +REL="NEXT" +TITLE="Object Files and Sections" +HREF="x564.html"></HEAD +><BODY +CLASS="SECTION" +BGCOLOR="#FFFFFF" +TEXT="#000000" +LINK="#0000FF" +VLINK="#840084" +ALINK="#0000FF" +><DIV +CLASS="NAVHEADER" +><TABLE +SUMMARY="Header navigation table" +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TH +COLSPAN="3" +ALIGN="center" +>LW Tool Chain</TH +></TR +><TR +><TD +WIDTH="10%" +ALIGN="left" +VALIGN="bottom" +><A +HREF="x520.html" +ACCESSKEY="P" +>Prev</A +></TD +><TD +WIDTH="80%" +ALIGN="center" +VALIGN="bottom" +>Chapter 3. LWASM</TD +><TD +WIDTH="10%" +ALIGN="right" +VALIGN="bottom" +><A +HREF="x564.html" +ACCESSKEY="N" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="SECTION" +><H1 +CLASS="SECTION" +><A +NAME="AEN543" +>3.8. Structures</A +></H1 +><P +> Structures are used to group related data in a fixed structure. A structure +consists a number of fields, defined in sequential order and which take up +specified size. The assembler does not enforce any means of access within a +structure; it assumes that whatever you are doing, you intended to do. +There are two pseudo ops that are used for defining structures. </P +><P +></P +><DIV +CLASS="VARIABLELIST" +><DL +><DT +><CODE +CLASS="PARAMETER" +>structname</CODE +> STRUCT</DT +><DD +><P +> This directive is used to begin the definition of a structure with name +<CODE +CLASS="PARAMETER" +>structname</CODE +>. Subsequent statements all form part of +the structure definition until the end of the structure is declared. </P +></DD +><DT +>ENDSTRUCT, ENDS</DT +><DD +><P +>This directive ends the definition of the structure. ENDSTRUCT is the +preferred form. Prior to version 3.0 of LWASM, ENDS was used to end a +section instead of a structure.</P +></DD +></DL +></DIV +><P +> Within a structure definition, only reservation pseudo ops are permitted. +Anything else will cause an assembly error.</P +><P +> Once a structure is defined, you can reserve an area of memory in the +same structure by using the structure name as the opcode. Structures can +also contain fields that are themselves structures. See the example +below.</P +><PRE +CLASS="PROGRAMLISTING" +>tstruct2 STRUCT +f1 rmb 1 +f2 rmb 1 + ENDSTRUCT + +tstruct STRUCT +field1 rmb 2 +field2 rmb 3 +field3 tstruct2 + ENDSTRUCT + + ORG $2000 +var1 tstruct +var2 tstruct2</PRE +><P +>Fields are referenced using a dot (.) as a separator. To refer to the +generic offset within a structure, use the structure name to the left of the +dot. If referring to a field within an actual variable, use the variable's +symbol name to the left of the dot.</P +><P +>You can also refer to the actual size of a structure (or a variable +declared as a structure) using the special symbol sizeof{structname} where +structname will be the name of the structure or the name of the +variable.</P +><P +>Essentially, structures are a shortcut for defining a vast number of +symbols. When a structure is defined, the assembler creates symbols for the +various fields in the form structname.fieldname as well as the appropriate +sizeof{structname} symbol. When a variable is declared as a structure, the +assembler does the same thing using the name of the variable. You will see +these symbols in the symbol table when the assembler is instructed to +provide a listing. For instance, the above listing will create the +following symbols (symbol values in parentheses): tstruct2.f1 (0), +tstruct2.f2 (1), sizeof{tstruct2} (2), tstruct.field1 (0), tstruct.field2 +(2), tstruct.field3 (5), tstruct.field3.f1 (5), tstruct.field3.f2 (6), +sizeof{tstruct.field3} (2), sizeof{tstruct} (7), var1 {$2000}, var1.field1 +{$2000}, var1.field2 {$2002}, var1.field3 {$2005}, var1.field3.f1 {$2005}, +var1.field3.f2 {$2006}, sizeof(var1.field3} (2), sizeof{var1} (7), var2 +($2007), var2.f1 ($2007), var2.f2 ($2008), sizeof{var2} (2). </P +></DIV +><DIV +CLASS="NAVFOOTER" +><HR +ALIGN="LEFT" +WIDTH="100%"><TABLE +SUMMARY="Footer navigation table" +WIDTH="100%" +BORDER="0" +CELLPADDING="0" +CELLSPACING="0" +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +><A +HREF="x520.html" +ACCESSKEY="P" +>Prev</A +></TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="index.html" +ACCESSKEY="H" +>Home</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +><A +HREF="x564.html" +ACCESSKEY="N" +>Next</A +></TD +></TR +><TR +><TD +WIDTH="33%" +ALIGN="left" +VALIGN="top" +>Macros</TD +><TD +WIDTH="34%" +ALIGN="center" +VALIGN="top" +><A +HREF="c62.html" +ACCESSKEY="U" +>Up</A +></TD +><TD +WIDTH="33%" +ALIGN="right" +VALIGN="top" +>Object Files and Sections</TD +></TR +></TABLE +></DIV +></BODY +></HTML +> \ No newline at end of file