Search found 2665 matches

by sirmorris
Tue Nov 21, 2017 10:23 pm
Forum: Hardware
Topic: TS1500 and ZXPand
Replies: 6
Views: 75

Re: TS1500 and ZXPand

They are a very worthwhile upgrade. It has to be said.
by sirmorris
Tue Nov 21, 2017 2:26 pm
Forum: Hardware
Topic: TS1500 and ZXPand
Replies: 6
Views: 75

Re: TS1500 and ZXPand

Nice job! However I feel I should warn about the fact that both the ZXpand and the TS1500 can simultaneously try to drive the bus when accessing RAM above 32k. When the '1500 has external memory pulling on its RAMCS line on the edge connector it remaps the internal 16k to sit at 32k. If you start PO...
by sirmorris
Tue Nov 21, 2017 8:45 am
Forum: Hardware
Topic: zx spectrum in zx81 case
Replies: 13
Views: 218

Re: zx spectrum in zx81 case

:ugeek: Superb.
by sirmorris
Mon Nov 20, 2017 7:22 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 23
Views: 322

Re: Help with Homemade ZX80-81- HIRES problem

Using a pencil and a piece of paper try to work out what address range the correct portion of the image occupies. This will give some clues I think.
by sirmorris
Mon Nov 20, 2017 6:36 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 23
Views: 322

Re: Help with Homemade ZX80-81- HIRES problem

Yes but do you see that the image is correct in that stripe? It looks to me like there is a problem with memory decoding. It seems that for a small region of the display it is correct, for the rest there is something happening. It would be interesting to see what address is correctly displayed.
by sirmorris
Mon Nov 20, 2017 5:31 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 23
Views: 322

Re: Help with Homemade ZX80-81- HIRES problem

I've only just noticed the band where the image looks correct, you have highlighted it in your original images. Is this static on screen or does it sweep from top to bottom?
by sirmorris
Mon Nov 20, 2017 4:10 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 23
Views: 322

Re: Help with Homemade ZX80-81- HIRES problem

This is from the ZXpand RAM select logic.

RAM = true when RAM is required.

assign IFRAMOE = !nRD | !nREFSH;
assign IFRAMCE = (!nMREQ | !nREFSH) & RAM

Also some WRX programs require RAM at 8k.

C
by sirmorris
Mon Nov 20, 2017 3:02 pm
Forum: Hardware
Topic: Help with Homemade ZX80-81- HIRES problem
Replies: 23
Views: 322

Re: Help with Homemade ZX80-81- HIRES problem

IIRC you need both. Wire RD and REFS with an AND gate.

Code: Select all


          +5v
           |
           || 10K
           |
!rd-----|<-+
!refsh--|<-+---!rdrefsh

by sirmorris
Sun Nov 19, 2017 3:30 pm
Forum: Hardware
Topic: ZX81 rebuild
Replies: 58
Views: 1323

Re: ZX81 rebuild

Lardo Boffin wrote:
Sun Nov 19, 2017 1:59 pm
I wimped out and bought one :( - I would have had to buy some bits in order to make my own.
No shame in that! You have enough on your plate ;)
by sirmorris
Sun Nov 19, 2017 3:17 pm
Forum: GAMES
Topic: Moon Patrol
Replies: 29
Views: 649

Re: Moon Patrol

The graphics look fine to me. Are you interested in getting more designs? I think in 2x2 characters you can do a few good ones.