Search found 107 matches
- Fri Nov 13, 2015 7:37 pm
- Forum: Development
- Topic: ZX81 / AMIGA music on... tapes / cassettes :)
- Replies: 21
- Views: 7897
Re: ZX81 / AMIGA music on... tapes / cassettes :)
Found mine but haven't had time to connect it yet
- Tue Oct 20, 2015 12:21 pm
- Forum: Development
- Topic: My new 1K demo
- Replies: 22
- Views: 7125
Re: My new 1K demo
Works perfectly on my Unmodified zeddy, Great, hmmm this is also proof that there is still something not quite right with my RAM-pack regarding WRX-compatibilty, i don't have time atm to solve this, but at least i do have a perfect tester !
- Tue Oct 06, 2015 10:04 pm
- Forum: Hardware
- Topic: Custom 64K RAM expansion for the ZX81
- Replies: 9
- Views: 7441
Re: Custom 64K RAM expansion for the ZX81
Very... Nice... Work !
- Tue Oct 06, 2015 9:48 am
- Forum: Hardware
- Topic: Memopak : bad RAM chips ?
- Replies: 96
- Views: 33529
Re: Memopak : bad RAM chips ?
The schematic in this post isn't actually the latest version, this is : Thx for that... and ouch! I won't even try to figure out what that circuit does! :mrgreen: It's not all that different from the other one, just /REFSN making sure that the characterset is available from the ROM ??? All i am doi...
- Mon Oct 05, 2015 11:14 pm
- Forum: Hardware
- Topic: Modifying a Sinclair ZX81 issue 1 - RAM
- Replies: 1
- Views: 1602
Re: Modifying a Sinclair ZX81 issue 1 - RAM
Nice work Mark !
- Mon Oct 05, 2015 8:37 pm
- Forum: Hardware
- Topic: Custom 64K RAM expansion for the ZX81
- Replies: 9
- Views: 7441
Re: Custom 64K RAM expansion for the ZX81
Keep me updated on your progress, the /RAMCS in this schematic seems to refer to /CE on the SRAM, if you're putting it on the edge, then /RAMCS should always be high, (A16 on the RAM either high or low, but consistent) /REFSN could also be wired in with /RD, it should effectively give you 56K RAM. S...
- Mon Oct 05, 2015 12:06 pm
- Forum: Hardware
- Topic: Memopak : bad RAM chips ?
- Replies: 96
- Views: 33529
Re: Memopak : bad RAM chips ?
You're beginning to "get it"... :D Sometimes i do and sometimes i don't, sometimes my info seems a tad incomplete let me see if i understand; if !MI is low, the part of RAM that is addressed should actually always be 4000h - 8000h (regardless of A15) since that is where the D-file is. More exactly:...
- Sun Oct 04, 2015 6:26 pm
- Forum: Hardware
- Topic: Memopak : bad RAM chips ?
- Replies: 96
- Views: 33529
Re: Memopak : bad RAM chips ?
Ah, maybe i've found a way around (and my earlier mistake) let me see if i understand; if !MI is low, the part of RAM that is addressed should actually always be 4000h - 8000h (regardless of A15) since that is where the D-file is. In other words, the chip should only be disabled(and the other disabl...
- Sun Oct 04, 2015 1:37 pm
- Forum: Hardware
- Topic: Memopak : bad RAM chips ?
- Replies: 96
- Views: 33529
Re: Memopak : bad RAM chips ?
Anyway, what i don't get is that my IO-port can disable the SRAM via !CE (if the A2-A15 are high and !MI and !(!MEMRQ) ) so the SRAM gets disabled for addresses FFFCh-FFFFh but when i do that for just A15 and !MI and !(!MEMRQ) then something goes wrong. Of course i have to keep disabling it in case ...
- Sun Oct 04, 2015 9:38 am
- Forum: Hardware
- Topic: Memopak : bad RAM chips ?
- Replies: 96
- Views: 33529
Re: Memopak : bad RAM chips ?
Hmm, I try and look for most Datasheets, had some trouble finding the logic table to the multiplexers though, Also in spite of many good efforts, some of the schematics are rather hard to read. One would actually expect that with all the HiRes capabilties and all they would not be made up out of das...