Sinclair ZX80 / ZX81 / Z88 Forums

You might also want to check out "Damper", aka Colour Clash on the Spectrum. Download here:

www.zx81.nl/dload/software/d/

This might be the worst advice ever, but: you could always just publish it and see what happens. Second that. If "just remove offending title if a copyright claim is received" works for you, then why not just go ahead. Ah yes, the -mostly theoretical- risk of legal problems / monetary damages etc. ...

Looks like close to standard composite voltage levels the modulator wants, apart from a DC bias (say, series capacitor or so?). Sadly there's no info on typical input impedance for that modulator. :?: it does mean that broken zeddies which are not comp modded won’t be fixable with this ULA (..) Quit...

@McKlaud and Andy: NICE!!! :) Especially Andy's 45-degree placement of the CPLD is likely how I'd have done it myself. The power consumption is roughly 250mA, but I have also got a 16KB SRAM chip on this board. I think I could go even lower if the 7805 were replaced with any decent DC-DC converter. ...

Soldering iron at hand?

ZX81 internal RAM expansion

TR2 acts like a buffer / 'enhancer' for the Z80 clock. So at the Z80 (pin 6) the clock signal should have much steeper edges (more like a block wave) than at the ULA output (pin 14). Seems to me that's not the case on several of the scope pics shown earlier. Which suggests that TR2 or surrounding co...

It would be great to have this game on the Zeddy! Looking at Lode Runner levels & thinking about how to take advantage of typical layouts, you could do something like this: 1) Start with background + one or two different types of bricks only. That would encode as a series of (few bits + length in si...

Funded!

Btw pictures show a Xilinx XC6SLX9 (Spartan-6 family). Which is kind of a low-end FPGA. But should provide plenty space for other machine implementations that aren't too complex.

There is no "one size fits all". For each application, determine: Whether you need 5V tolerance on I/O pins. 5V tolerant devices will need 3.3V power (or less), but I/O's can be hooked up directly. For non-5V tolerant devices, signals from a 5V system will need a voltage shifter (IC), series resisto...

Thx everyone for your answers! :) So TV screen simply turns blank - sometimes black, gray(ish) or even white. And with the TV losing sync, prompting some TV's to go for a blue screen or display a message. Fwiw: that actually matches what I'm seeing with -my- composite modded ZX81's: a blank, white s...