RE: [N8VEM-S100:1645] IMSAI 8080 CPU card replacement

[Crusty OMO <crus...@hotmail.com>]

Hi John,

My design definitely requires refinement to make it IEEE696 compliant.  It started off as a single board replacement, but if we are going to make it into a nice board, it needs more attention to the S-100 details.  I'm neck deep in my next project at the moment (building a Floppy Disk reader at the read pulse level).  But when I can get my prototype back in my hands, I'll continue this design (and add the Altair connector).

I should be getting my Alair in a couple of weeks, so I'll shelve this project until then.  If anyone has time to work on it, then I'd love to get more advise.

PS. How should Phantom work?  Does it just override the Chip Select of the RAM?

PPS. I have the book "Interfacing to S-100 / IEE696 microcomputers" by Sol Libes and Mark Garetz.  Very good book, feel free to reference any pages in it.

:)J

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From: mon...@vitasoft.org
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:1645] IMSAI 8080 CPU card replacement
Date: Fri, 10 May 2013 21:14:43 -0700

Absolutly minimally Josh the IEEE-696 upper address lines (A16-A20) need to be pulled to ground (via a 74LS244 or something).  Take a look at the pin designations. See here:- http://s100computers.com/History.htm  (bottom of page) for all the lines.  Make sure Phantom like is working correctly. May want to pull to ground Data lines 7 to 15 for port I/O’s. These for starts.

 

John

 

 

John Monahan Ph.D

e-mail: mon...@vitasoft.org

Text:    mon...@txt.att.net

 

 

From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Crusty OMO
Sent: Friday, May 10, 2013 4:29 PM
To: n8vem...@googlegroups.com
Subject: RE: [N8VEM-S100:1641] IMSAI 8080 CPU card replacement

 

John,

One more thing about this board...
As is, it runs great, but perhaps it could use a little more flexibility.

It has the full 64K (local on the same board), but I'm thinking perhaps it should have less or optionally allow some address space from the S-100 bus.
ie, jumper select blocks of address space that are to be gotten from the S-100 bus?

Comments?

:) Josh

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