Interrupt handler
Posted: Mon Jan 11, 2021 12:36 pm
Hi all,
I know this comes up from time to time and I've looked through the forum for clues and one post had something promising but I'm stuck.
I'm starting to learn machine code and I'm pretty good now but I want to be able to do something like the 'nova' prgram does and that's put some thing on the screen the whole time. To do this i need to 'hook' the screen routine and call my code after it's drawn.
There's a post that has some code by Dr Beep and I've tried this but it doesn't work. What I think it does is change the ix register to point to the new routine so it is called instead of the ROM code and you do what you need to do in there as well as calling the ROM code that would have run anyways.
I use EO and in the debugger after I've run the code the IX register has recovered it's old value and my code isn't being called. Stepping through the ROM is difficult for me and a bit confusing. I've tried it before asking for help....
Here's the code I'm basing my stuff on:
if anyone can tell me what's wrong that would be brilliant thank you!!!
I know this comes up from time to time and I've looked through the forum for clues and one post had something promising but I'm stuck.
I'm starting to learn machine code and I'm pretty good now but I want to be able to do something like the 'nova' prgram does and that's put some thing on the screen the whole time. To do this i need to 'hook' the screen routine and call my code after it's drawn.
There's a post that has some code by Dr Beep and I've tried this but it doesn't work. What I think it does is change the ix register to point to the new routine so it is called instead of the ROM code and you do what you need to do in there as well as calling the ROM code that would have run anyways.
I use EO and in the debugger after I've run the code the IX register has recovered it's old value and my code isn't being called. Stepping through the ROM is difficult for me and a bit confusing. I've tried it before asking for help....
Here's the code I'm basing my stuff on:
Code: Select all
programmestart:
LD IX,mycode
loop:
; wait for vsync
; do some things
jp loop
mycode CALL #281 ; the normal IX routine
myprog CALL mystuff ;
end CALL #292
CALL #220
LD IX,mycode
JP #2A4
mystuff:
do my stuff
ret