Dave, I have Dr. Wilcox's hand-written errata and notes for the text as I picked them up a couple of years ago. If I have time this weekend, I'll try to review and if I find anything significant to the problem I'll scan and post for you. I haven't started building my 68k board yet, although I have Dr. Wilcox's original wire-wrapped board. Regards, Brian.
On Thursday, July 17, 2014 10:23:30 PM UTC-4, yoda wrote: > Hi John, > > Re-wiring the circuit gives no noticeable difference. I see between 40 > and 50 ns delay of release of data after pWR* going high. I don't know if > that is enough or not. I attached a typical trace here. If you look at > pages 331-337 of Wilcox he discusses the circuit and the issue with write. > The circuit is not the same as in the schematics on page 494-495 as the > logic and path lengths have been changed. I am not sure what to do - the > console I/O and serial I/O are working fine but I am not sure on the IDE > board yet - I need to but the logic analyzer on the 8255 or IDE port and > look at what data is being put on the ports and make sure it matches what I > am sending. I probably have a couple of days of debugging here so if you > want to wait on pushing the design out until I have the IDE board working > with it, I would feel more comfortable. > > Also in your write up in the end you state that jumpering P2 3-4 makes all > S100 bus I/O have 2 wait states - the way I read the schematic you are > adding 2 wait states to M1 pgm fetches. I think you want to jumper 4 to 1 > or 7,9 for 2 waits on I/O accesses. Look at 479 as it gives several > examples as how to set the jumpers. > > The net of above - no matter what frequency you run at, U37, U38, U42 and > U40 (if you can find one) need to all be F logic. The state machine is > independent of processor frequency (I think Pontius found that in his bring > up and is in his reference notes on the wiki). > > Dave > -- 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.
