Sinclair ZX80 / ZX81 / Z88 Forums

Why all those complications? shouldn't be easy to put a label at the right instruction in ../lib/target/zx81/zx81_altint_core.asm, to make that label global so your #asm block can see it as a label and you only need to write "ld (display3_back_to_rom_isr+1),hl" ? You are right, I just did it, much ...

Ok it works now ! The address in my case is 0x4179, so the hook code that installs the ISR is now: void hook(void) { #asm ld hl,_DisplayISR ld (0x4179),hl #endasm } I found the way to identify the correct address examining the crt initialization code located in ../lib/target/zx81/zx81_altint_core.as...

So the address may be located by disassembling the P file and looking for the end of the alternative DISPLAY-3: 4167 ed44 neg 4169 3c inc a 416a 08 ex af,af' 416b d3fe out (0feh),a 416d 2a8b41 ld hl,(418bh) 4170 23 inc hl 4171 228b41 ld (418bh),hl 4174 7c ld a,h 4175 b5 or l 4176 c27d41 jp nz,417dh...

The z88dk documentation I found about IM1 https://www.z88dk.org/wiki/doku.php?id=library:interrupts#im_1 says this: IM 1 Response to a maskable interrupt is to jump to a fixed ISR at address 0×38 that must terminate in “EI;RET” or “EI;RETI” (latter preferred). The best way to accommodate this mode i...

Just a note that the clock available here https://sinclairzxworld.com/viewtopic.php?p=17265#p17265 hooks up an ISR, but I don't remember all details... The address of a C function (although consisting of assembly code) is "poked" to the startup code of the ISR that z88dk installed, at 0x41b4.The so...

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 do...

Could you point me somewhere to find info on how it works ? not really strong in MC, that's why I'm trying to do it from C

Thank you Dr. Beep !

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 t...

Thank you !

Also interested, I hope someone have the files