Hi John, If you are definitely going ahead with a V2 of the 80386 CPU board then the 8+8 back to back byte feature that you have previously mentioned (for the 8bit S100 XGVA board compatibility) would be a great feature, not sure how much extra work that would involve for you though ??
best regards David Fry On Sunday, February 8, 2015 at 4:48:00 AM UTC, monahanz wrote: > Perhaps the following might help Gary… > > In my travels is working with the 80486-40 I noticed that with one (of my > two) SMB-V2’s it would not switch back to the Z80 using the Output a 1 to > bit 0 of port 0EEH. > > > > However if I jumpered K3 2-3 so it used only 8 bit port addressing and > that immediately corrected the problem. > > > > When I set K3 to 1-2 (16 bit port addressing) the problem returned. I > suspected the problem is U31B is not getting the address lines up in time > on its pin 5 to clock the correct data into U33. If I use a 74F138 for > U27 and a 74F10 for U18 the problem disappeared. I.e. I could always > switch back to the Z80. > > > > Could you try these in your system. > > > > John > > > > > > > > *From:* [email protected] <javascript:> [mailto: > [email protected] <javascript:>] *On Behalf Of *Gary Kaufman > *Sent:* Saturday, February 7, 2015 9:27 AM > *To:* [email protected] <javascript:> > *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 > > > > > > -- > You received this message because you are subscribed to the Google Groups > "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
