mirror of
https://github.com/gbdev/rgbds.git
synced 2025-11-29 06:17:48 +00:00
more HTML formatting gunk
This commit is contained in:
Anthony Bentley
@@ -1,121 +1,60 @@
|
||||
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
|
||||
"http://www.w3.org/TR/html4/loose.dtd">
|
||||
<HTML>
|
||||
<HEAD>
|
||||
<TITLE>xAsm MACRO/ENDM</TITLE>
|
||||
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
|
||||
<html>
|
||||
<head>
|
||||
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
|
||||
<title>xAsm MACRO/ENDM</title>
|
||||
<link rel="stylesheet" type="text/css" href="../style.css">
|
||||
</HEAD>
|
||||
|
||||
<BODY>
|
||||
<I><H2>MACRO<BR>
|
||||
ENDM</H2></I><HR>
|
||||
|
||||
<P>One of the best features of an assembler is the ability to write macros for it. Macros also provide a method of passing
|
||||
arguments to them and they can then react to the input using IF-constructs.<BR>
|
||||
<BR>
|
||||
<TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
|
||||
<TR>
|
||||
<TD><FONT COLOR="#00FF00">
|
||||
<PRE>MyMacro: MACRO
|
||||
</head>
|
||||
<body>
|
||||
<h1>MACRO, ENDM</h1>
|
||||
<p>One of the best features of an assembler is the ability to write macros for it. Macros also provide a method of passing arguments to them and they can then react to the input using IF-constructs.</p>
|
||||
<pre>MyMacro: MACRO
|
||||
ld a,80
|
||||
call MyFunc
|
||||
ENDM</PRE>
|
||||
</FONT></TD>
|
||||
</TR>
|
||||
</TABLE>
|
||||
<P>The above example is a very simple macro. You execute the macro by typing its name.<BR>
|
||||
<BR>
|
||||
<TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
|
||||
<TR>
|
||||
<TD><FONT COLOR="#00FF00">
|
||||
<PRE> add a,b
|
||||
ENDM</pre>
|
||||
<p>The above example is a very simple macro. You execute the macro by typing its name.</p>
|
||||
<pre> add a,b
|
||||
ld sp,hl
|
||||
MyMacro ;This will be expanded
|
||||
sub a,87</PRE>
|
||||
</FONT></TD>
|
||||
</TR>
|
||||
</TABLE>
|
||||
<P>When the assembler meets MyMacro it will insert the macrodefinition (the text enclosed in <B>MACRO/ENDM</B>).
|
||||
<P id="labelsuffix">Suppose your macro contains a loop.<BR>
|
||||
<BR>
|
||||
<TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
|
||||
<TR>
|
||||
<TD><FONT COLOR="#00FF00">
|
||||
<PRE>LoopyMacro: MACRO
|
||||
sub a,87</pre>
|
||||
<p>When the assembler meets MyMacro it will insert the macrodefinition (the text enclosed in <b>MACRO/ENDM</b>).</p>
|
||||
<p id="labelsuffix">Suppose your macro contains a loop.</p>
|
||||
<pre>LoopyMacro: MACRO
|
||||
xor a,a
|
||||
.loop ld [hl+],a
|
||||
dec c
|
||||
jr nz,.loop
|
||||
ENDM</PRE>
|
||||
</FONT></TD>
|
||||
</TR>
|
||||
</TABLE>
|
||||
<A TARGET="#labelsuffix"></A><P>This is fine. That is, if you only use the macro once per <A HREF="labels.htm">scope</A>. To get around this problem there is a special label string equate called <B>\@</B> that you can append to your labels and it will then expand to a unique string.
|
||||
<B>\@</B> also works in <A HREF="rept.htm">REPT-blocks</A> should you have any loops there.<BR>
|
||||
<BR>
|
||||
<TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
|
||||
<TR>
|
||||
<TD><FONT COLOR="#00FF00">
|
||||
<PRE>LoopyMacro: MACRO
|
||||
ENDM</pre>
|
||||
<p>This is fine. That is, if you only use the macro once per <a href="labels.htm">scope</a>. To get around this problem there is a special label string equate called <b>\@</b> that you can append to your labels and it will then expand to a unique string.</p>
|
||||
<p><b>\@</b> also works in <a href="rept.htm">REPT-blocks</a> should you have any loops there.</p>
|
||||
<pre>LoopyMacro: MACRO
|
||||
xor a,a
|
||||
.loop\@ ld [hl+],a
|
||||
dec c
|
||||
jr nz,.loop\@
|
||||
ENDM</PRE>
|
||||
</FONT></TD>
|
||||
</TR>
|
||||
</TABLE>
|
||||
<H4>Arguments</H4>
|
||||
<P>I'd like <I>LoopyMacro</I> a lot better if I didn't have to pre-load the registers with values and <I>then</I> call it.
|
||||
What I'd like is the ability to pass it arguments and it then loaded the registers itself.
|
||||
<P>And I can do that. In macros you can get the arguments by using the special macro string equates <B>\1</B> through
|
||||
<B>\9</B>, <B>\1</B> being the first argument specified on the calling of the macro.<BR>
|
||||
<BR>
|
||||
<TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
|
||||
<TR>
|
||||
<TD><FONT COLOR="#00FF00">
|
||||
<PRE>LoopyMacro: MACRO
|
||||
ENDM</pre>
|
||||
<h2>Arguments</h2>
|
||||
<p>I’d like <i>LoopyMacro</i> a lot better if I didn’t have to pre-load the registers with values and <em>then</em> call it. What I’d like is the ability to pass it arguments and it then loaded the registers itself.</p>
|
||||
<p>And I can do that. In macros you can get the arguments by using the special macro string equates <b>\1</b> through <b>\9</b>, <b>\1</b> being the first argument specified on the calling of the macro.</p>
|
||||
<pre>LoopyMacro: MACRO
|
||||
ld hl,\1
|
||||
ld c,\2
|
||||
xor a,a
|
||||
.loop\@ ld [hl+],a
|
||||
dec c
|
||||
jr nz,.loop\@
|
||||
ENDM</PRE>
|
||||
</FONT></TD>
|
||||
</TR>
|
||||
</TABLE>
|
||||
<P>Now I can call the macro specifying two arguments. The first being the address and the second being a bytecount.
|
||||
The macro will then reset all bytes in this range.<BR>
|
||||
<BR>
|
||||
<TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
|
||||
<TR>
|
||||
<TD><FONT COLOR="#00FF00">
|
||||
<PRE> LoopyMacro MyVars,54</PRE>
|
||||
</FONT></TD>
|
||||
</TR>
|
||||
</TABLE>
|
||||
<P> You can specify up to nine arguments when calling a
|
||||
macro. Arguments are passed as string equates. There's no need to enclose them in quotes. Parameter passing has changed a bit since v1.03 in that an expression will not be evaluated first but passed directly. This means that it's probably a very good idea to use
|
||||
brackets around \1-\9 if you perform further calculations on them. For instance if you pass 1+2 as the first argument and then do
|
||||
ENDM</pre>
|
||||
<p>Now I can call the macro specifying two arguments. The first being the address and the second being a bytecount. The macro will then reset all bytes in this range.</p>
|
||||
<pre> LoopyMacro MyVars,54</pre>
|
||||
<p>You can specify up to nine arguments when calling a macro. Arguments are passed as string equates. There’s no need to enclose them in quotes. Parameter passing has changed a bit since v1.03 in that an expression will not be evaluated first but passed directly. This means that it’s probably a very good idea to use brackets around \1–\9 if you perform further calculations on them. For instance if you pass 1+2 as the first argument and then do <code> PRINTV \1*2</code>
|
||||
you will get the value 5 on screen and not 6 as you might have expected.</p>
|
||||
<p>Note that a colon (:) following the macro-name is required. Macros can't be exported or imported. It's valid to call a macro from a macro (yes, even the same one).</p>
|
||||
|
||||
<P><TABLE BORDER=0 BGCOLOR="Black" CELLPADDING=8 WIDTH="50%">
|
||||
<TR>
|
||||
<TD><FONT COLOR="#00FF00">
|
||||
<PRE> PRINTV \1*2
|
||||
</PRE>
|
||||
</FONT></TD>
|
||||
</TR>
|
||||
</TABLE>
|
||||
|
||||
you will get the value 5 on screen and not 6 as you might have expected..<BR>
|
||||
|
||||
<P>Note that a colon (:) following the macro-name is required. Macros can't be exported or imported. It's valid to call a macro from a macro (yes, even the same one).<BR>
|
||||
|
||||
<H3>See also:</H3>
|
||||
<UL>
|
||||
<LI><A HREF="shift.htm">SHIFT</A>
|
||||
</UL>
|
||||
|
||||
<BR><HR>
|
||||
<FONT SIZE="-1"><I><P ALIGN=RIGHT>Last updated 02 July 1997 by <A HREF="mailto:surfsmurf@matilde.demon.co.uk">Carsten Sorensen</A></P></I></FONT>
|
||||
<h1>See also:</h1>
|
||||
<ul>
|
||||
<li><a href="shift.htm">SHIFT</a>
|
||||
</ul>
|
||||
<hr>
|
||||
<p>Last updated 02 July 1997 by <a href="mailto:surfsmurf@matilde.demon.co.uk">Carsten Sorensen</a></p>
|
||||
</body>
|
||||
</html>
|
||||
|
||||
Reference in New Issue
Block a user