Sinclair ZX80 / ZX81 / Z88 Forums

Hi,

Just want to hear if someone has build the CHR$X16 as described by Wilf?
I'm asking, because I've tried but ran into some smaller issued - just want to hear from someone, that it can be done, before diving into more detailed investigation of my board.

It looks semi ok, but as can be seen - there is something odd going on when outputting line 2 and forward. (Don't mind the ZERO, I forgot to redesign it )

OK - so after 3 tries it finally pays off - got a version running that seems to be working fine. Only thing is that font table is selected by setting I=n*4 only, and not adding 224 as described in Wilfs documentation. Not sure if its mine that has a flaw in the wiring or eprom programming - but hey, it's working (the 00 in the 0 is my "debug" info, as each font has table number in "0")

Prototype on breadboard

Great work.

I've previously bought the componts for this circuit, but didn't find the time to put it together.

The main problem with this circuit, I think, is that the charsets are stored in ROM and not in RAM. Maybe this can be solved by replacing the ROM with FRAM or Flash. But the circuit somehow need to support updating the FRAM or Flash.