re: A86: RAM Page $80 ??

To: assembly-86@lists.ticalc.org
Subject: re: A86: RAM Page $80 ??
From: Pat Milheron <pmilheron@ti.com>
Date: Tue, 12 Aug 1997 13:09:25 -0700
Conversation-Id: <Pine.LNX.3.95.970811233934.660B-100000@S-98-190.resnet.ohio-state.edu>
In-Reply-To: <Pine.LNX.3.95.970811233934.660B-100000@S-98-190.resnet.ohio-state.edu>
Reply-To: assembly-86@lists.ticalc.org

Port 6 is used to switch RAM pages in the address space 8000h -BFFFh.

You are right this is not the exact code you had seen. 

Valid values to be written to this port are 41h - 47h, ram pages 1 - 7.

Later,
Pat

P.S. DO BE DO BE DO

------------------
Original text

From: Dan Eble <eble@cis.ohio-state.edu>, on 8/11/97 10:56 PM:

I was snooping around in the ROM, as I am wont to do, and stumbled across
a piece of code that does something like this: (this is not exact)

     ld a,$80
     out (6),a
     ld a,(somewhere)
     ld ($8000),a

Then it restores the previous RAM page.  When I send $80 to port 6, every
byte in $8000-BFFF reads as $1A.  My first thought was that this might be 
some kind of memory-mapped I/O, but when I write various values to
($8000), nothing happens.  Anyone have any ideas?

--------
Dan Eble (mailto:eble@cis.ohio-state.edu)
         (http://www.cis.ohio-state.edu/~eble)

Follow-Ups:

re: A86: RAM Page $80 ??

From: Dan Eble <eble@cis.ohio-state.edu>

References:

A86: RAM Page $80 ??

From: Dan Eble <eble@cis.ohio-state.edu>