Traveling until Thursday Phillipe, so cannot help, possibly a 74xx14 instead of 74xx04, may be of use somewhere in the circuit. John
John Monahan ([email protected]) On Oct 12, 2014 4:07 AM, "Philippe Elie" <[email protected]> wrote: > hi folks, > I finally identified the issued that made some CPM (non banked version) > hang the system : the RAM bank switching system had a timing issue. More > specifically, when the monitor initializes the D2/D3 ports (with 00 and 04 > respectively) the second IO access was actually trigerring also a 04 write > into the D2 port. > I solved the issue by replacing U25 74LS04 by a 74F04 but a little glitch > on D2 port enable still appears that makes me a bit concern about the > reliability : > > > <https://lh4.googleusercontent.com/-c8bEDnJl8u0/VDpcsyQu39I/AAAAAAAAANY/Zt15ihLoU_g/s1600/Z80%2BD2%2Btiming.jpg> > I was wondering whether the problem would come from sOUT : for U39 I used > a 74LS08 instead of a 74S08 thinking speeds would be the same and > considering the CPU operates at 4Mhz ? Do you that would fix the problem ? > > thanks in advance for your feedback > Philippe > > -- > 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. > -- 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.
