Am 27. August 2019 00:28:58 schrieb silverdr_at_wfmh.org.pl: >> On 2019-08-27, at 00:16, André Fachat <afachat_at_gmx.de> wrote: >> >> Am 27. August 2019 00:05:07 schrieb silverdr_at_wfmh.org.pl: >> >>>> On 2019-08-26, at 23:24, Mia Magnusson <mia_at_plea.se> wrote: >>>> >>>>> It might be easier to do what Commodore has done in the 1570/71 and >>>>> use an additional 6526 just for the shift register. Then borrow the >>>>> code from the 1571. >>>> >>>> That would most likely be the solution that requires the least amount >>>> of work to get it up and running. >>>> >>>> Captain Obvious says that the con is of course that it needs a CIA. For >>>> a one-off or general DIY project that might not be a problem, but if >>>> someone were to order a bunch of PCBs and sell either as a complete kit >>>> or ready-built thing it might be troublesome to source CIAs. >>> >>> Pulling a CIA's shift register off a PLD would be Captain Obvious next >>> advice ;-) >> >> And then you need to add logic to put this CPLD somewhere into the CPU >> address space. > > Yes. > >> Ok that probably goes into the CPLD as well :-) > > And yes :-) > > I have somewhat similar (PIAs parallel port) done for the next Dolphin and > its parallel connection. This allowed to drop all the six (sic!) glue > logic ICs AND the full VIA/CIA/PIA chip in favour of one CPLD. Interesting. What CPLD do you use? with 5V tolerance? What supply voltages are needed? Through hole package? Which one (DIP, PLCC, ...) > > >> You also need to make sure you have the right output drivers. > > True. Works for me so far but the parallel is a bit different (directly > wired to the CIA through USER PORT) Yeah, there you can use totem pole drivers (std TTL or even CMOS). In the IEC case with potentially multiple drivers you need something like open collector drivers.... André >Received on 2020-05-29 22:56:53
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