You can use a de-bounce hardware switch circuit if you like Gary (two NAND gates for example). Best would be to be on the safe side and use an OC gate to drive the line as well, but if you are sure there is no other gate active on the line you should be OK with the NAND gate output.
Good luck
John
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of Gary Kaufman
Sent: Saturday, February 7, 2015 9:27 AM
To: n8vem...@googlegroups.com
Subject: Re: [N8VEM-S100:6234] Re: 80386 CPU Board - Correction of Correction
John -
Ok, see the Z80 pull ups now...
Interestingly when I was confirming that I had the correct resistors on the 80386 board I noticed that "in circuit" R1 and R8 measure 500 ohms. This makes sense for R1 with P36 jumpered 1-2 and 3-4. I haven't thought thru R8 (master reset) yet.
I tried the "external port" approach with a simple switch, but I think I was getting too much switching bounce to draw any conclusions. I'll wire up the port hopefully tonight.
- Gary
On 2/7/2015 11:57 AM, John Monahan wrote:
Early morning here, coffee has not kicked in yet! Should read:-
Yes, on the Z80 board (RR5) Gary. Remember only one, 1K pull-up per S100 bus OC line. You can get away with two but you are overloading the gate (now 500 Ohms), more, then you will have severe signal slew, more, then unstable signals.
Any luck with the “external port” approach?
John
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