Sinclair ZX80 / ZX81 / Z88 Forums

The pull-ups perform two purposes 1. any address not handed by the rom or ram would always be read as FF. 2. TTL pull-ups are quite weak, which is why the logic 1 voltage is quite a bit lower than 5V. The pull-ups would help drag this voltage higher, especially as the data has passed through resist...

Hi there ! I don't know what is a MSX but I am very glad to hear about your ULA work. Seems like people work either on programming emulators or developping ULA's. Good to hear because I have to replace a nonworking ULA (no pixel output). As I heard you are running at 13 MHz - does your ULA (or CPLD ...

Thanks Andy. I will think tomorrow of it, now it's a little bit late for that stuff. :mrgreen: By the way, I changed my schematic of video with logic gates for generating a back porch without LM1881 as a member request from the german forum. Just for information. Two whom it may concern. ;) Video-HQ...

Erm can't think of any other programs that put black pixels in the back porch area, that was the only one i found that did it. Rezzurection does it too, but that requires hi-res also... Okay - hi-res could be maybe different. But how can the program do this with normal video mode ? If you have pixe...

By the way I had some problems with my plasma TV when putting out many invers characters on the screen. It had problems with synchronizing. But this effect was only via RF modulator / antenna input. My video input was steady and clear with this picture. Any more ideas what to test with video ? Thank...

the scroller of which outputs black video during the backporch region of the video signal... on my original circuit using an LM1881 the video would distort a little on the scroller, but the newer version does not suffer from that. I am not sure what you mean. I think the program can only use the st...

Here full screen picture

over RF modulator / antenna input and over video input

25thanni is a multipart demo written by Bodo Wenzel a good few years ago to celebrate the 25th Anniversary of our beloved Zeddies. As the program has about 9kBytes I can not run this because I do not have the possibility to load programs at this time. And the program uses HRG graphics as well (okay...

Thank you very much, PokeMon. I'll give it a try... ;) If you use the second one with 74LS06 you should use a lower resistor for output of the driver. R9,R10,R11 should be 2,2k instead of 22k. I just tried something other and was not happy with change between low and high when digitizing the clock ...

have you tried this in normal video mode with 25thanni, the scroller of which outputs black video during the backporch region of the video signal... on my original circuit using an LM1881 the video would distort a little on the scroller, but the newer version does not suffer from that. Hääää ? What...