Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!ncar!asuvax!mcdphx!hrc!gtephx!campbellb
From: campbellb@...!asuvax!gtephx (Brian Campbell)
Newsgroups: comp.sys.apple2
Subject: Re: ML subroutines (passing parameters in ML)
Summary: Yes, but...
Message-ID: <1991May2.154829.1842@...!asuvax!gtephx>
Date: 2 May 91 15:48:29 GMT
References: <3397@kluge.fiu.edu> <13845@ucrmath.ucr.edu> <1991Apr30.170428.17156@nevada.edu>
Organization: gte
Lines: 13

In article <1991Apr30.170428.17156@nevada.edu>, alfter@nevada.edu (SCOTT ALFTER) writes:
> In article <1991Apr29.203359.250@...!asuvax!gtephx> campbellb@...!asuvax!gtephx (Brian Campbell) writes:
> >on the 6502).  It looks like this: (i,S) which I take to mean, access the
> >word at offset i relative to the Stack pointer.
> Not present on the 6502?  You could always do a TSX followed by a
> LDA $100,X to do that.  (Want even more random access?  The stack is
> in a fixed location; just grab a byte anywhere from $100 to $1FF.)

True, but what I meant was an addressing mode supported in single instruction,
and *relative* to the stack pointer.  The TSX, LDA $100,X is a neat trick though,
although it takes 4 bytes vs. 2 for an LDA (i,S) in the 65816.  Grabbing a byte
via LDA $1xx is rarely useful, because you generally need to access relative
(the R word again) to the Stack pointer.