Sinclair ZX80 / ZX81 / Z88 Forums

This guy on eBay sells PCBs for ZX81 in these models: ZX81NU - ZX81 clone without ULA - PCB ZX81+38 rev1.9 MAHJONGG Clone 2017 Wilco ZX80 ZX81 rev1.1 PCB 2017 Wilco ZX81 ZX80 rev1.1 GOLDET - Black PCB 2017 GOLD PLATED - Wilco ZX81 ZX80 rev1.1 - Green PCB Maybe that can be used? https://www.ebay.com/...

Thank mr. Oliver. He is the genius behind the software and hardware: https://forum.tlienhard.com/phpBB3/viewtopic.php?t=3360

I did buy a €100 mini hot plate (3x3cm) on AliExpress. Now I can easily solder SOIC and TSSOP ICs. That was a great investment for me.

blittled wrote: ↑Wed Jul 12, 2023 11:43 pm Will you have some CPLDs programmed for sale?

From what I read in the repository, you just connect the PCB to your PC via USB, and use the free Arduino software to upload a sketch to the ATMEGA controller. The software detects a firmware on the SD card, and updates the CPLD with it.

The numbers 0 - 9 on the ZX81 is character number 28 to 37. Thus if you have a number between 0 and 9, and add 28, you get the characters '0' to '9'.

It first divides the number by 100. But there is not divide on the Z80 CPU. So it subtracts 100, multiple times, and when there is not more hundreds, it displays the counter, and then displaying the first number (the 100s). Then it continues to divide by 10, and again that is by subtracting 10s, and...

If you output to the screen via RST $10, you will output the character belonging to the value in register A. If you want to output a 16-bit number in decimal, the easiest way is to set the BC register, and return to basic, to print it. I might have misunderstod you completely. Please come with an ex...

Yes, I think you should POKE it in. And don't edit the line afterwards. I think that would destroy the code.

Looks very interesting. Looking forward for more.

Sinclair just wanted to make a cheap computer. So they made the memory map very simple: Address 0 - 16k would be ROM, even though only 8k ROM is installed. Address 16k - 32k would be RAM. 1k internal RAM, or 16k external RAM pack. External RAM disables the internal 1k of RAM. Address 32k - 64k is us...