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Update html and pdf documentation in preparation for release
| author | William Astle <lost@l-w.ca> |
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| date | Fri, 03 May 2019 20:06:17 -0600 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/docs/manual/x585.html Fri May 03 20:06:17 2019 -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="x562.html"><LINK +REL="NEXT" +TITLE="Object Files and Sections" +HREF="x606.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="x562.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="x606.html" +ACCESSKEY="N" +>Next</A +></TD +></TR +></TABLE +><HR +ALIGN="LEFT" +WIDTH="100%"></DIV +><DIV +CLASS="SECTION" +><H1 +CLASS="SECTION" +><A +NAME="AEN585" +>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="x562.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="x606.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