Search found 1287 matches

by dr beep
Thu Jun 11, 2020 12:35 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 1880

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

if I got it right, with no device feeding the bus, IM2 will catch any floating byte there and crash ? I guess this is far beyond my technical knowledge :) So if i'm correct, the alternative left is to implement a routine that is called after the display is done, I'm not sure if that's possible to d...
by dr beep
Sun Jun 07, 2020 7:19 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 1880

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

Hello, I'm trying to learn how interrupts work on the ZX81 with z88dk. This im2 mode code crashes but it works fine on the Spectrum. I also read that it's possible to install an isr that's called every time the screen is rendered, that is 50 or 60 times each second, anyone knows if that's possible ...
by dr beep
Sat Jun 06, 2020 10:23 pm
Forum: Emulators
Topic: SP-2-ZX81, the new ZX81-emulator for the 48K ZX Spectrum
Replies: 6
Views: 1395

Re: SP-2-ZX81, the new ZX81-emulator for the 48K ZX Spectrum

Well,

A quick scan on WIKIPEDIA tells me that on a ENTERPRISE a full speed ZX81 emulator must be possible, like the SAM-coupe or a ZX Spectrum 128 with interface. Bankswitching must be possible to set memory in order and update screen during intrupt.




Johan "Dr Beep" Koelman
by dr beep
Sat May 30, 2020 10:06 pm
Forum: GAMES
Topic: Random maze generation game
Replies: 4
Views: 613

Re: Random maze generation game

I did a quick glimpse into the machinecode.

Did you write machinecode or did you crosscompile from C?
by dr beep
Sat May 23, 2020 8:53 pm
Forum: Software
Topic: ZX81 Basic programs loading from shadow ROM
Replies: 15
Views: 1244

Re: ZX81 Basic programs loading from shadow ROM

where do you ldir your program, must be #4009.
#676 is after LINERUN so you execute the next BASIC line of the program.
by dr beep
Thu May 21, 2020 7:59 pm
Forum: Software
Topic: ZX81 Basic programs loading from shadow ROM
Replies: 15
Views: 1244

Re: ZX81 Basic programs loading from shadow ROM

This is the RET-address after LINE-RUN.
If a line holds SAVE then the next line is run.
LOAD continues then where SAVE ended.

Normally a LOAD ends in a screendisplay at #207 which will decrease FRAMES 1x, that is why I suggest doing that too.
You will need it to load my 1K games.
by dr beep
Thu May 21, 2020 7:38 pm
Forum: Software
Topic: ZX81 Basic programs loading from shadow ROM
Replies: 15
Views: 1244

Re: ZX81 Basic programs loading from shadow ROM

Try #676..... I do that in my emulator, but AFTER manually decreasing FRAMES 1x for my games to load.
by dr beep
Thu May 21, 2020 9:57 am
Forum: Software
Topic: ZX81 Basic programs loading from shadow ROM
Replies: 15
Views: 1244

Re: ZX81 Basic programs loading from shadow ROM

After LDIR just jump to #3E5
See LOAD at #340 and jump at #361.


https://k1.spdns.de/Vintage/Sinclair/80 ... Hara).html
by dr beep
Wed May 20, 2020 8:23 pm
Forum: Software
Topic: ZX81 Basic programs loading from shadow ROM
Replies: 15
Views: 1244

Re: ZX81 Basic programs loading from shadow ROM

Hi I am new to this forum, so first of all hello to all :) I am currently doing a little project where I want to pimp my old ZX81. I am doing the internal 16k static RAM mod, no need for that wobbly blue tacked fizzing RAM pack anymore. I am also replacing the ROM with a 27C512 with a simple latch ...
by dr beep
Tue May 19, 2020 10:00 pm
Forum: Emulators
Topic: SP-2-ZX81, the new ZX81-emulator for the 48K ZX Spectrum
Replies: 6
Views: 1395

Re: SP-2-ZX81, the new ZX81-emulator for the 48K ZX Spectrum

I coded a whole new version to add speed to the emulation. On 3 points speed could be won: 1) When each opcode would have its own mainroutine 10 tstates per opcode should be won. The intruptroutine needed to be called anytime to get this working and all opcodes would get extra code. 2) Split A from ...