Subject: Re: Question on 65816.
Newsgroups: comp.sys.apple2.programmer
From: dempson@actrix.gen.nz (David Empson)
Date: Sat, 5 Aug 2000 14:36:34 +1200
Message-ID: <1eewaij.as8x0t162wauqN%dempson@actrix.gen.nz>
References: <39872A21.BC1D7E6F@wanadoo.fr>
Organization: Empsoft
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Babar de Saint Cyr <NO_babardesaintcyr_SPAM@wanadoo.fr> wrote:

> A very simple question about 65816 but I cannot find
> any answer in all my 816'doc.
> 
> When in full 16 bits mode I do:
> ...
> blabla   lda    toto
> ...
> ...
> toto     dc     i'0'
> ...
> 
> Is
> toto THEN toto+1
> *OR*
> toto+1 THEN toto
> octets read from memory to fill A register ???

The actual physical memory accesses would be toto, then toto+1.  This is
documented in the 65816 data sheet, with a big chart showing the
cycle-by-cycle operation of each addressing mode.  Entry 2a (Absolute)
is the appropriate one for the LDA instruction.

Of course the data is stored in the usual little-endian format, so toto
contains the low order data byte and toto+1 contains the high order data
byte.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P O Box 27-103, Wellington, New Zealand