Posted By
siz
on 2020-12-02
08:42:54
|  Re: Cartridge and raster interrupts
DO NOT copy $fc00-$ffff area as $fd00-$ff3f is unmappable I/O area. All these routines reside from $fc00-$fcff.
There is a copy of the reset routine at $fff6 and the reset and interrupt vectors at $fffc/$fffd and $fffe/$ffff. (These are initialized by KERNAL)
The KERNAL interrupt handler just saves the registers, checks if the interrupt source was external or a BRK instruction and does an appropriate indirect jumps to ($0314/$0315) or ($0316/$0317). The default interrupt handler vector value at $0314/$0315 is $ce0e
If you do this yourself you don't need to use the KERNAL routines.
If you want to run your interrupts from your cartridge ROM you have to:
- set $0314/$0315
- set an interrupt source (for example raster interrupt)
- make sure $fb contains your ROM bank number
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