The Sinclair QL Forum

Theodoulos Liontakis posted on the Sinclair QL For Everyone Facebook group that he has successfully created a CPLD replacement for the ZX8301.

This link will likely not work unless you are a member of the group:

https://www.facebook.com/photo/?fbid=54 ... 4457487075

Here is a picture:

It works with everything I have tested (not much) including my version of qubide card (832K ram) and the Micro Peripherals floppy controller.
I haven't implemented the flash bit because I can't fit it in EPM7128S CPLD, but I have ready the code for a EPM7160 CPLD and waiting for the ic I ordered from China to test it.
I made a new pcb that will work with either 7128S or 7160S and also has a buffer for the video signal for better quality but I haven't ordered it yet.

Pretty cool, well done. I've started doodling something similar a while back with a XC95144XL but as I got a ton of replacement ZX8301 I never felt the need to finish it

Then I was thinking about doing a FPGA version that directly outputs a VGA signal but that makes it a lot more complicated and with current chip prices it's no fun anyway.

I've found ZX8301's hard to find. I located one source (Mutant Caterpillar) for a reasonable price, but glad a replacement is out there.

Will this become an open source project (github) once complete?

The ZX8302 it the other custom chip that hasn't been recreated, correct?

Maybe I'll make it public, not sure about the source code, maybe just the CPLD programming file and the pcb.

lliont wrote:also has a cd4050 buffer for the video signal for better quality but I haven't ordered it yet.

Would video output also benefit from ESD protection?

M68008 wrote: Would video output also benefit from ESD protection?

Even if something gets damaged from ESD it would be a cheap chip

The reason I add the buffer is a flicker I noticed in the 256x512 mode in some patterns and I think the buffer can drive the video outputs better.
By the way if someone has to suggest of a suitable video buffer (but cheap and easy to get) please do, I haven't ordered the pcb yet so I can still make changes.
I have a lot of 74LS241 buffer/line drivers -15/24ma, 12ns, 133 Ohm load maybe those are ok, I'll see.
I'm sure the LS chip is less sensitive to ESD.

bwinkel67 wrote:I've found ZX8301's hard to find. I located one source (Mutant Caterpillar) for a reasonable price, but glad a replacement is out there.

If you live in UK the price is reasonable, I live in Greece and a ZX8301 from ebay with price 35 pounds cost me 62 pounds after customs (Brexit) and shipping fees.
With that amount I developed the replacement, with about double the sum I could have bought another QL maybe.

Hi,

I would prefer the CPLD replacement then the code could modified, rather than fixed chip.

Could I make one myself?

I'll inform when I finish and test the next-better version.