Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!interlan.InterLan.COM!interlan.interlan.com!yetsko
From: yetsko@interlan.interlan.com (Mike Yetsko)
Newsgroups: comp.sys.tandy
Subject: Re: 3rd 3-port card?
Message-ID: <YETSKO.90Nov27143921@interlan.interlan.com>
Date: 27 Nov 90 19:39:21 GMT
References: <188@rwing.UUCP>
Reply-To: yetsko@interlan.interlan.com
Organization: Racal InterLan, Inc., Boxborough, MA (1-800-LAN-TALK)
Lines: 16
In-reply-to: nanook@rwing.UUCP's message of 27 Nov 90 10:43:46 GMT

I've put up to 4 3-port cards in a Tandy, just continue with the logical
progressions on the switch settings.  I think I had to do something
kludgey with the software though, but it worked fine.

There is a caveat with the boards though.  The Z80 spec says you can only
daisey chain 4 devices for EIN-EIO and have iterrupt arbitration work
correctly and reliably.  What you can do is wither modify the boards
so that EIN is passed to EIOUT with a gate in parallel ored with the
on-board signal to act as a fast 'look-ahead' or just put Z80B parts
in for the CTCs in all the boards, as their signal propogation is
faster on the enable interrupt passthrough.

Sorry I can't get more specific, but it's been a LONG time since I
did anything with a Tandy Model II series machine.

Mike Yetsko