135 lines
5 KiB
HTML
135 lines
5 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
|
|
|
|
<!--Converted with LaTeX2HTML 99.1 release (March 30, 1999)
|
|
original version by: Nikos Drakos, CBLU, University of Leeds
|
|
* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
|
|
* with significant contributions from:
|
|
Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
|
|
<HTML>
|
|
<HEAD>
|
|
<TITLE>3.10 Functions using private banks</TITLE>
|
|
<META NAME="description" CONTENT="3.10 Functions using private banks">
|
|
<META NAME="keywords" CONTENT="sdccman">
|
|
<META NAME="resource-type" CONTENT="document">
|
|
<META NAME="distribution" CONTENT="global">
|
|
|
|
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
|
|
<META NAME="Generator" CONTENT="LaTeX2HTML v99.1 release">
|
|
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">
|
|
|
|
<LINK REL="STYLESHEET" HREF="sdccman.css">
|
|
|
|
<LINK REL="next" HREF="node30.html">
|
|
<LINK REL="previous" HREF="node28.html">
|
|
<LINK REL="up" HREF="node19.html">
|
|
<LINK REL="next" HREF="node30.html">
|
|
</HEAD>
|
|
|
|
<BODY >
|
|
<!--Navigation Panel-->
|
|
<A NAME="tex2html682"
|
|
HREF="node30.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A>
|
|
<A NAME="tex2html676"
|
|
HREF="node19.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A>
|
|
<A NAME="tex2html670"
|
|
HREF="node28.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="previous_motif.gif"></A>
|
|
<A NAME="tex2html678"
|
|
HREF="node1.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents_motif.gif"></A>
|
|
<A NAME="tex2html680"
|
|
HREF="node61.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index_motif.gif"></A>
|
|
<BR>
|
|
<B> Next:</B> <A NAME="tex2html683"
|
|
HREF="node30.html">3.11 Absolute Addressing</A>
|
|
<B> Up:</B> <A NAME="tex2html677"
|
|
HREF="node19.html">3. Using SDCC</A>
|
|
<B> Previous:</B> <A NAME="tex2html671"
|
|
HREF="node28.html">3.9 Naked Functions</A>
|
|
  <B> <A NAME="tex2html679"
|
|
HREF="node1.html">Contents</A></B>
|
|
  <B> <A NAME="tex2html681"
|
|
HREF="node61.html">Index</A></B>
|
|
<BR>
|
|
<BR>
|
|
<!--End of Navigation Panel-->
|
|
|
|
<H2><A NAME="SECTION000410000000000000000">
|
|
3.10 Functions using private banks</A>
|
|
</H2>
|
|
|
|
<P>
|
|
The <I>using</I> attribute (which tells the compiler to use a register
|
|
bank other than the default bank zero) should only be applied to <I>interrupt</I>
|
|
functions (see note 1 below). This will in most circumstances make
|
|
the generated ISR code more efficient since it will not have to save
|
|
registers on the stack.
|
|
|
|
<P>
|
|
The <I>using</I> attribute will have no effect on the generated code
|
|
for a <I>non-interrupt</I> function (but may occasionally be useful
|
|
anyway<A NAME="tex2html1"
|
|
HREF="footnode.html#foot531"><SUP>1</SUP></A>).
|
|
<BR>
|
|
<I>(pending: I don't think this has been done yet)</I>
|
|
|
|
<P>
|
|
An <I>interrupt</I> function using a non-zero bank will assume that
|
|
it can trash that register bank, and will not save it. Since high-priority
|
|
interrupts can interrupt low-priority ones on the 8051 and friends,
|
|
this means that if a high-priority ISR <I>using</I> a particular bank
|
|
occurs while processing a low-priority ISR <I>using</I> the same bank,
|
|
terrible and bad things can happen. To prevent this, no single register
|
|
bank should be <I>used</I> by both a high priority and a low priority
|
|
ISR. This is probably most easily done by having all high priority
|
|
ISRs use one bank and all low priority ISRs use another. If you have
|
|
an ISR which can change priority at runtime, you're on your own: I
|
|
suggest using the default bank zero and taking the small performance
|
|
hit.
|
|
|
|
<P>
|
|
It is most efficient if your ISR calls no other functions. If your
|
|
ISR must call other functions, it is most efficient if those functions
|
|
use the same bank as the ISR (see note 1 below); the next best is
|
|
if the called functions use bank zero. It is very inefficient to call
|
|
a function using a different, non-zero bank from an ISR.
|
|
|
|
<P>
|
|
<HR>
|
|
<!--Navigation Panel-->
|
|
<A NAME="tex2html682"
|
|
HREF="node30.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="next_motif.gif"></A>
|
|
<A NAME="tex2html676"
|
|
HREF="node19.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="up_motif.gif"></A>
|
|
<A NAME="tex2html670"
|
|
HREF="node28.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="previous_motif.gif"></A>
|
|
<A NAME="tex2html678"
|
|
HREF="node1.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="contents_motif.gif"></A>
|
|
<A NAME="tex2html680"
|
|
HREF="node61.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="index_motif.gif"></A>
|
|
<BR>
|
|
<B> Next:</B> <A NAME="tex2html683"
|
|
HREF="node30.html">3.11 Absolute Addressing</A>
|
|
<B> Up:</B> <A NAME="tex2html677"
|
|
HREF="node19.html">3. Using SDCC</A>
|
|
<B> Previous:</B> <A NAME="tex2html671"
|
|
HREF="node28.html">3.9 Naked Functions</A>
|
|
  <B> <A NAME="tex2html679"
|
|
HREF="node1.html">Contents</A></B>
|
|
  <B> <A NAME="tex2html681"
|
|
HREF="node61.html">Index</A></B>
|
|
<!--End of Navigation Panel-->
|
|
<ADDRESS>
|
|
<I>Johan Knol</I>
|
|
<BR><I>2001-07-13</I>
|
|
</ADDRESS>
|
|
</BODY>
|
|
</HTML>
|