Path: utzoo!attcan!uunet!husc6!mailrus!ames!pasteur!ucbvax!RADC-TOPS20.ARPA!GUBBINS
From: GUBBINS@RADC-TOPS20.ARPA (Gern)
Newsgroups: comp.sys.zenith.z100
Subject: Re: Using Compupro SPUZ z80 slave board with z100
Message-ID: <12401209688.11.GUBBINS@RADC-TOPS20.ARPA>
Date: 25 May 88 20:39:23 GMT
References: <8805240228.AA28221@mathvax.MSI.CORNELL.EDU>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 11

The 8088 in the Z-100 uses only 20 address lines A0-A19 of the S-100
bus.   The top 4 (A20-A23) are held by the High-Order-Address-Latch
which is a Port (init set to zero).  This effectively banks 16 1Mbyte
address spaces for the 8088.   The 8085 latches A16-A23 as well if
operating.  To my knowledge, this port has never been put to use with
either processor.  The S-100 bus, the DMA of the Z-100 Winnie, and the
NETcard, all are 24-bit masters (TMA).  The latch port tri-states for
TMA (Temporary Master Access - 696 lingo for DMA/DIA (direct I/O access)).

Gern
-------