Search found 337 matches

by McKlaud
Mon Mar 19, 2018 3:15 pm
Forum: Hardware
Topic: Keyboard beeper
Replies: 3
Views: 1811

Re: Keyboard beeper

Nice.

By the way, have you tried the keyboard beeper?
by McKlaud
Mon Mar 19, 2018 3:09 pm
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 238
Views: 123546

Re: ZX81 ULA-in-a-CPLD

I all Zeddys that I've got the NEC Z80 clone is sitting. The uPD780C datasheet is referring to:
  • Address lines 50pF
  • Data lines 200pF
200pF load looks like an extreme for me.
by McKlaud
Sun Mar 18, 2018 1:03 pm
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 238
Views: 123546

Re: ZX81 ULA-in-a-CPLD

It seems that I am back on the track. The ULA is alive, works in FAST mode only, loads some BASIC software, reads keyboard, execute BASIC command. Furthermore I ran a BASIC benchmark and its execution time was the same like my other Zeddy in the FAST mode. Regarding "SLOW" mode, see the screen shoot...
by McKlaud
Sun Mar 18, 2018 12:43 pm
Forum: Development
Topic: Bad Apple UDG
Replies: 23
Views: 10913

Re: Bad Apple UDG

:shock: :shock: :shock:

My jaws dropped to the floor and can't lift them up.
by McKlaud
Sat Mar 17, 2018 12:24 am
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 238
Views: 123546

Re: ZX81 ULA-in-a-CPLD

I am back to square one. No proper keyboard reads, my Zeddy boots to the "K" prompt in the FAST mode only, a lot of noise on the ground plane of the Zeddy PCB and the noise is visible in the video signal too. :cry:
by McKlaud
Thu Mar 15, 2018 1:55 pm
Forum: Development
Topic: Tzxduino
Replies: 3
Views: 3033

Re: Tzxduino

Hi Bill, I use one, precisely it is the Zaxon's variant of TZXDuino ( SMR ). It works well with any .p and .o files for ZX80/ZX81. These formats have been supported by the TZXDuino firmware for a while since its rev. 1.3 was released in May 2017. The current F/W is in rev. 1.81 or so. I can post som...
by McKlaud
Wed Mar 14, 2018 7:24 pm
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 238
Views: 123546

Re: ZX81 ULA-in-a-CPLD

Yes. See below
by McKlaud
Tue Mar 13, 2018 11:17 pm
Forum: Development
Topic: do we still use UHF modulators ?
Replies: 17
Views: 7955

Re: do we still use UHF modulators ?

Thanks Andy. I did more searching in a few places including forgotten folders on my hard drive and I've found it. :geek:
by McKlaud
Tue Mar 13, 2018 10:46 pm
Forum: Development
Topic: do we still use UHF modulators ?
Replies: 17
Views: 7955

Re: do we still use UHF modulators ?

Has anyone got any schematic diagram or datasheet of the UM1233 modulator? I would appreciate if you could share it, please.
by McKlaud
Tue Mar 13, 2018 10:05 pm
Forum: Development
Topic: do we still use UHF modulators ?
Replies: 17
Views: 7955

Re: do we still use UHF modulators ?

Paul,

In my case the cost is a secondary issue, because we are talking about difference in voltage levels at the pin 16 of the ULA only. The development time could be longer but I think, both variants are feasible.