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From: sealbrec@acs.ucalgary.ca (Alvin Albrecht)
Newsgroups: comp.sys.amstrad.8bit,comp.sys.sinclair
Subject: Re: Port used in Z80 block I/O instructions?
Date: 9 Jan 1996 23:10:11 -0700
Organization: The University of Calgary
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Message-ID: <4cvl83$jn4@acs5.acs.ucalgary.ca>
References: <4cuam7$hgk@lyra.csx.cam.ac.uk>
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In article <4cuam7$hgk@lyra.csx.cam.ac.uk>,
M.G. Rison <rison@hep.phy.cam.ac.uk> wrote:
>I'm fairly certain that the value used for OUTI/OUTD is the value
>*after* B has been cremented.  Somehow I seem to think the value used
>for INI/IND is the value *before*, however.  Could someone give me an
>_authoritative_ answer?  No guesses, please!
>
>Mark
>
>======================================================================
>|   rison@hep.phy.cam.ac.uk       |  Esperanto - lingvo inter-nacia  |
>|   rison@vxcern.cern.ch          |       * Mi estas riisto *        |
>======================================================================

The reference I use is "The Programming Guide to the Z80 Chip" by
Philip R. Robinson.  He lists the sequence of actions taken during
each instruction.

OUTD, OUTI : decrement B before putting it on the bus
INI, IND: put B on the bus before decrementing

So it looks like you guessed right.


Alvin