FPGA replacment for the ZX8301 ULA and more

[Peter]

We can try slower access times even I don't like to make it slower

Okay let's try that. Do you have schematics and placeplan for me, so I can see where the JTAG lines are?

[Peter]

[...] maybe you where observing the beginning of the video memory read accesses where there is not problem even in your case.

Possible, I just had a hasty look without checking what kind of access it was.

For the undershoot maybe I can enable the reduced slew rate option of the cpld if you think that is a problem.

Yes, the lowered slewrate is important. Even that is still fast for a QL mainboard.
I don't expect this to cause my specific problem though.

DRam is HM4864p-2

This also indicates we might have a DRAM related timing issue. For example max. transition times of "my" DRAM is 100ns, of "your" DRAM 35 ns.

[lliont]

jtag.png (3.3 KiB) Viewed 794 times

Insert the pins to the holes of the board and apply a small steady sideways force while programming to ensure contact.
You need to supply power to the board, I do it on the QL but don't take the risk.
Or send them to Stephan who has done this before.

[Derek_Stewart]

Hi,

I have a Tetroid Power Regulator in place of the standard QL power Regulator and heat sink:

That is the only difference I can see, I can not see any problems with the ULA board send to me.

Is there any commands I can try to test the operation of the ULA?

If I am disturbing the discussion, I am sorry.

[lliont]

Thanks for the info Derek


Programming the cpld

[Peter]

Is there any commands I can try to test the operation of the ULA?

You could check if you really also have KM4646A-15 DRAMs.

Insert the pins to the holes of the board and apply a small steady sideways force while programming to ensure contact.
You need to supply power to the board, I do it on the QL but don't take the risk.
Or send them to Stephan who has done this before.

I found a parallel port adaptor, which will probably no longer be supported. So I have ordered a USB one.
The cost of a programming adaptor does not justify shipping to Stephan and back. Especially as we don't know how many programming cycles we will need until it works here.

Do I need the bloated Quartus II installation, or is there a leaner programming tool?

[lliont]

I use Quartus 13.0.1 for the older cpld programming, newer quartus versions may not support MAX7000S family.
Some usb blaster clone's driver crashes windows 10, work well with earlier versions of windows.

[Derek_Stewart]

You could check if you really also have KM4646A-15 DRAMs.

I have TMS4164-15NL DRAMs soldered to the QL board:

[lliont]

Well there is no doubt it has to do with dram but is it that all QLs with KM4646A-15 DRAMs have the incompatibility problem?

I had an idea, in my QL I installed sockets for the drams so if I find KM4646A-15 DRAMs I can directly test them.
Are you sure the dram type is spelled correctly Peter? I think you mean KM4164A
The KM4164B-12 work without a problem you can see in older pictures that half of the drams in my issue 5 QL are this kind.
I found also 3 ics KM4164B-15 to test

[lliont]

Well I reproduced the problem.
Initially QL booted but after a while problems appeared i.e. random pixels on the screen, then I made some changes and now it works.
I think I solved it but I'll give it some more time.

Tested with only 3 of these @##$% dram ics.