You probably have a lot of space in the GALs for logic? On Wednesday, February 11, 2015 at 8:18:00 PM UTC-6, monahanz wrote: > > So you’re suggesting latching the RD*/Data signals as well then Roger > using a 74LS373 and an inverted RD* (RD) as I did for the writes. This > unfortunately will require another IC chip (I have run out of inverter > gates) but not a problem, plenty of room on this board. > > > > Could everybody take a look at this schematic and let me know what you > thing. (Remember LS373’s accept the data when clock is high, latch it when > clock returns low. The OE*’s will be low/on for as long as the CPU will > allow (sINP or sOUT high). > > > > John > > > > *From:* [email protected] <javascript:> [mailto: > [email protected] <javascript:>] > *Sent:* Wednesday, February 11, 2015 5:02 PM > *To:* [email protected] <javascript:> > *Subject:* Re: [N8VEM-S100:6296] Re: An updated (V3) version of our Dual > IDE/CF card S100 bus board > > > > > > >> One confusing thing is in what respect are we talking about read and > write. In terms of the S100 bus/CPU or > >>the 8255. Let’s talk in terms of the CPU. > > >> Dave since you feel the problem is just with the CPU WR* signal > (particularly the 68K), then I will go back to > >>using the 74LS244 for the CPU read (S100 bus DI lines). > > When I designed my 68K SBC, I had a great deal of difficulty with the 68K > R/W* signal (particularly with reads, as I remember it). I was able to get > a CF to work well with the Z80 (two SBC's) directly (no 8255), but the CF > seems to like a clean write or read pulse, and the 68K R/W* just didn't > seem to do it. I had to go with an 8255 to get the CF to work with a 68K. > And it works quite well that way. Maybe that's what you need to focus on > with the 68K CPU card (clean up R/W*)??? > > Roger > > > > > > > > -- > 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. >
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