CPLD replacement for ZX8301

[Peter]

I hate to say it, but GoldCard and SuperGoldcard rise and fall times are too fast for the QL mainboard, causing ringing and crosstalk beyond the TTL thresholds. This works with the slow logic of the original, but could be a problem with modern CPLDs. Also it could be that your timings are simply too far away from the original ULA.

[martyn_hill]

Hi Peter!

I hate to say it, but GoldCard and SuperGoldcard rise and fall times are too high for the QL mainboard, causing ringing and crosstalk beyond the TTL thresholds.

I guess you meant '...rise and fall times are too low/fast...'

[lliont]

I think the timing of my ULA is now very close to the original so maybe I need to look for a way to deal with the "noise" produced by the GC/SGC, maybe by adding small resistors in series with the signals. The photos I saw with the random pixels could be related to ringing problems.

[Peter]

I guess you meant '...rise and fall times are too low/fast...'

Yes of course, thank you. Original post editet now.

[lliont]

I think I fixed the problem with the cpld ula and Gold and Super Gold Card.
In my QL they both work now. No artifacts and both boot.

Thank you Vitaliy (tetroid) for the card to test.

I attached a gotek and run programs and everything seems ok.

[Maskenlos]

Hi Leon,

that sounds great.
Could you go a little bit more into details about the cause of the problems and the solution?
It would be quite interesting if the existing versions could be upgraded, for example mine or the version Peter has.

Thanks and best regards,

Stephan

[lliont]

Hi, it had to do with dram refreshing.
I can send you a new programming file or send me the boards to reprogram them.
I'll tell you when I am ready.

[Popopo]

Oh!
This was the project for ZX8301 on CPLD!
Niceeee thank you a lot.

I will read about it now carefully.

[martyn_hill]

Hi Leon!

I think I fixed the problem with the cpld ula and Gold and Super Gold Card.
In my QL they both work now. No artifacts and both boot.

That's great news!

Would you be able to share the revised CPLD JED so I can re-program my (basic) ULA replacement unit?

Warm regards

[lliont]

Yes I'll soon send you email