Search found 4 matches

by hlide
Sat Jun 13, 2020 2:51 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 20090

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

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" ?
by hlide
Fri Jun 12, 2020 12:37 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 20090

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

Yes, I expected that float byte to be $FF in most case if nothing else can disturb. Since it is an odd address at the end of a page, it means it will call a routine accross the page I and page I+1. I thought Z88DK can handle mode 1 and mode 2. Is there no im1_init function?
by hlide
Tue Jun 09, 2020 10:02 pm
Forum: Development
Topic: ZX81 interrupts with z88dk, how to install an ISR ?
Replies: 19
Views: 20090

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

Let me explain. First, the ZX81 ROM uses IM1 and address 0x38 to service interrupts, which should raise some questions about the feasability to use IM2. Why? in IM2, the address of the routine to service the interrupt is given by register I and an identifier set by the device interrupting the CPU th...
by hlide
Sun Jun 07, 2020 5:31 pm
Forum: Development
Topic: Using sll with z80asm Version 1.8
Replies: 6
Views: 8930

Re: Using sll with z80asm Version 1.8

Thanks for trying it out. I wasn't aware that this is no official Zilog instruction. It seems that I have to consider another assembler then or stick to the mundane, something like SLA A OR 1 nah, use something like DB $CB,$37 ; SLL A Why? OR will affect C flag in the wrong way if you want to use i...