Sinclair ZX80 / ZX81 Forums

Do not know Joachim's "Eiermaler"? If not, here it is..

http://forum.tlienhard.com/phpBB3/viewt ... f=2&t=2278

FYI:

Joachim controls his (old and small) lathe with a ZX81:

http://forum.tlienhard.com/phpBB3/viewt ... =2&p=38419

Siggi

McKlaud wrote: ↑

Thu Dec 06, 2018 11:33 pm

And don't forget about 10k resistor between pins 27 & 28.

.. which is not necessary for this use case

Maybe it has been necessary for ram extensions, which had a battery (to write-protect the ram during power-off state) ...

Siggi

Also, if you press the CONT key, your first routine will print another screen of characters... Thats because the JR NZ tests the value of the A Register, you are decrementing BC. No, JR NZ tests the Z-flag, which is part of the F register. It could be set by a lot of instructions (like "DEC C" or "...

See there:
http://www.zx81stuff.org.uk/zx81/hardwa ... emental16K

http://www.zx81stuff.org.uk/zx81/hardwa ... Fitted.jpg

Siggi

Maybe it does not solve the current problem, but usually each chip should have its own capacitor (around 10-100nF), connected across its power pins to stabilize its power supply. If those C are missing, the board may run (because the logic is OK), but not very stable (because the power supply of a ...

Maybe it does not solve the current problem, but usually each chip should have its own capacitor (around 10-100nF), connected across its power pins to stabilize its power supply. If those C are missing, the board may run (because the logic is OK), but not very stable (because the power supply of a c...

(Mrs Moggy lets me have the good single malt to bring in the new year) For information only: I have done several compatibility tests of Whiskey and the ZX81: Failure: http://forum.tlienhard.com/phpBB3/download/file.php?id=6100 Success: http://forum.tlienhard.com/phpBB3/download/file.php?id=6103 htt...

Hi Mike I next printed out the PCB layout files and meticulously did a point-by-point check of all connections, finding no shorts or dead spots. Did you check/measure on the PCB or on the contact inside the socket (maybe soldering is the problem)? Soldering all components again often solves such pro...

I started my program on a "Sinclair Diet", but I don't think I'm going to make the 2K finish line without some major loss of functionality, Without losing functionality a lot of bytes can be lost ;) Replace if condition1 then PRINT string1 if condition2 then PRINT string2 by print string1 AND condt...