Search found 922 matches

by siggi
Mon Nov 09, 2020 10:25 am
Forum: Hardware
Topic: How to power off the ZX81 correctly
Replies: 15
Views: 380

Re: How to power off the ZX81 correctly

I recommend to use the following shutdown program:

Code: Select all

call FAST
HALT
Then you can pull the plug ...

:mrgreen:
Siggi
by siggi
Wed Oct 07, 2020 10:06 am
Forum: Sinclair Misc
Topic: Where can I find "true" ZX81 fonts
Replies: 18
Views: 7557

Re: Where can I find "true" ZX81 fonts

I still have a lot of punched cards, when I learned PASCAL programming. I will check, whether I also have some old Cobol programs I once wrote ...

Siggi
by siggi
Mon Oct 05, 2020 12:07 pm
Forum: Sinclair Misc
Topic: Where can I find "true" ZX81 fonts
Replies: 18
Views: 7557

Re: Where can I find "true" ZX81 fonts

Do you know Wilf's NOVA? It supports "BASIC line number trace". Maybe that could be used to implement Single Stepping at Basic level... http://www.user.dccnet.com/wrigter/index_files/nova2005.htm And Single Stepping in Z88DK compiled C programs would also be nice to have :mrgreen: https://www.z88dk....
by siggi
Sun Oct 04, 2020 1:35 pm
Forum: Hardware
Topic: Anyone already build this kit?
Replies: 5
Views: 3785

Re: Anyone already build this kit?

Is there a schema of the board?
32KB is enough ram for a lot of ZX81 applications. But having 40KB ram, it would be possible to use more ZeddyNet applications, which run above 32K and are 16K in size. So I would need to add more ram ....

Siggi
by siggi
Sun Oct 04, 2020 11:34 am
Forum: Hardware
Topic: Strange memory expansion
Replies: 6
Views: 3369

Re: Strange memory expansion

I have a board of the same (probably German) company (for an enhanced character set). To use 64K ram, some kind of paging-logic is needed to switch different ram block to the same address area "seen" by the Z80 (e. g. 2 16kB pages at address 32K-48K). Thus an output latch (typically 8 bit) is needed...
by siggi
Sat Oct 03, 2020 7:19 pm
Forum: Hardware
Topic: Strange memory expansion
Replies: 6
Views: 3369

Re: Strange memory expansion

I don't see any pics.

Is it that board on the left side of the picture?

https://forum.tlienhard.com/phpBB3/view ... 866#p32866

That is a 64K ram pack, having also an 8 bit output port, e. g. for remote control of a cassette recorder and for paging of ram banks

Siggi
by siggi
Thu Sep 24, 2020 3:38 pm
Forum: Software
Topic: Camouflage
Replies: 4
Views: 4341

Re: Camouflage

Years ago I played around with that program. But it ran faster than the music. Is it designed for a 50 Hz or a 60 Hz Zeddy? Maybe the speed was not OK, because I had used a patched rom (for faster BASIC FOR/NEXT) in my Zeddy. Maybe nowadays, when using a ZX81x2 rom, the turntable must run at 45 rpm,...
by siggi
Sat Aug 29, 2020 12:26 pm
Forum: Hardware
Topic: RAM keeps failing
Replies: 9
Views: 5770

Re: RAM keeps failing

There might be a timing problem, which occurs using modern and fast ram chips. See there: https://www.sinclairzxworld.com/viewtopic.php?p=2620#p2620 " The problem is the old design of the ZX80/81, where the internal RAM's output drivers are enabled together with the complete chip ( /CE conneted to /...
by siggi
Thu Jun 11, 2020 7:53 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 11864

Re: ZX81 interrupts with z88dk, how to install an ISR ?

FYI: old feature request for Z88DK about this topic: https://www.z88dk.org/forum/viewtopic.php?id=4877 old thread about this topic: https://www.sinclairzxworld.com/viewtopic.php?p=31046#p31046 BTW: in my ZX81-MIDI-Player I am using the ZX81 NMI interrupt generator to make the MIDI clock. Of course t...