Search found 2264 matches

by PokeMon
Wed Oct 05, 2011 10:14 pm
Forum: Hardware
Topic: video signal ZX81 old/new version
Replies: 11
Views: 8373

video signal ZX81 old/new version

I have now 2 ZX81, one old version (1980) and one new version (1981, ISS3). I found quitely different video signal on both ULA's. My old ZX81 works properly but has a picture with very small contrast due to missing back porch. The new ZX81 has back porch but is not working properly, only a grey back...
by PokeMon
Tue Oct 04, 2011 9:33 pm
Forum: Emulators
Topic: My new emulator
Replies: 43
Views: 36295

Re: My new emulator

Most of the reason I started the project is that I want to gain a better understanding of how things operate at the electrical level, the corollary being that I'll probably make many missteps along the way. Why don't you buy an oscilloscope or a logic analyzer to see what's going on ? So you are no...
by PokeMon
Tue Oct 04, 2011 9:30 pm
Forum: Emulators
Topic: My new emulator
Replies: 43
Views: 36295

Re: My new emulator

Most of the reason I started the project is that I want to gain a better understanding of how things operate at the electrical level, the corollary being that I'll probably make many missteps along the way. Why don't you buy an oscilloscope or a logic analyzer to see what's going on ? So you are no...
by PokeMon
Tue Oct 04, 2011 9:15 pm
Forum: Sinclair Misc
Topic: Letter perfect printer for a zx81
Replies: 7
Views: 5038

Re: Letter perfect printer for a zx81

dr beep wrote:And please don't read interface as in her face!
I spend an "s" for you. Guess where. :mrgreen:
by PokeMon
Mon Oct 03, 2011 10:10 pm
Forum: Hardware
Topic: Beginner's sync questions
Replies: 23
Views: 11534

Re: Beginner's sync questions

You will probably need to refresh the page in your browser, as it should show the update date of "2nd October 2011" near the top. ...any ideas how I can force page invalidation, as I often need to do a forced page refresh in by browser (Firefox) when I have updated a page. Just set a meta tag in yo...
by PokeMon
Mon Oct 03, 2011 7:57 pm
Forum: Sinclair Misc
Topic: Letter perfect printer for a zx81
Replies: 7
Views: 5038

Re: Letter perfect printer for a zx81

Cool stuff.
Maybe I can use my ZX81 as secretary. :mrgreen:
by PokeMon
Mon Oct 03, 2011 7:53 pm
Forum: Software
Topic: Timex Sinclair TS 1500 vs. Sinclair Spectrum
Replies: 6
Views: 4670

Re: Timex Sinclair TS 1500 vs. Sinclair Spectrum

Actually, I have just sold a Spectrum to a user in the USA - having done the composite video modification, he then plans to use this to connect to the TV - see http://www.youtube.com/watch?v=tqnIa4rXK_c for some help on using a UK based Spectrum in the USA. I think a video modification is not neces...
by PokeMon
Sat Oct 01, 2011 8:34 pm
Forum: Hardware
Topic: Beginner's sync questions
Replies: 23
Views: 11534

Re: Beginner's sync questions

Maybe this information can help as well. http://www.user.dccnet.com/wrigter/index_files/ZX81WAIT.htm He's talking about Jitter which can occure when executing code till interrupt takes effect. This is done via wait states and synchronizing to NMI. I don't know if this refers to original hardware or ...
by PokeMon
Fri Sep 30, 2011 9:02 pm
Forum: Hardware
Topic: Beginner's sync questions
Replies: 23
Views: 11534

Re: Beginner's sync questions

@Thommy Maybe this will be helpful for you as well. Wilf Righter has explained many details of the ZX81 video signal generation, but has many more interesting articles. http://www.user.dccnet.com/wrigter/index_files/ZX%20Video%20Tutorial.htm http://www.user.dccnet.com/wrigter/ Also this could be hel...
by PokeMon
Thu Sep 29, 2011 12:21 am
Forum: Sinclair Misc
Topic: Saving variables
Replies: 2
Views: 2653

Re: Saving variables

right now, on the zx81 / ts1000 if you want to save variables with your program you can but when you load it you have to do a goto to restart the program, running erases them. I don't understand the problem. Why use RUN when you can use GOTO for not destroy variables ? By the way you can save a pro...