AndyH wrote:Joy1 is in ZP but should be in a safe spot.
That's what I also thought sometimes ...
I can move to regular RAM to test also.
... better safe than sorry.
I know Backbit has an option (by default) to point to it's own routines and I believe I can switch back to the kernal which I'll look into.
That actually doesn't tell me much. Of course I'd suppose Backbit wedges in own KERNAL routines, but the question remains whether they actually need to fiddle around with DDRA of VIA #1 - IF that's actually the issue!
I should also add that I currently have my own VBL interrupt running that bypasses the regular keyboard scan. Hopefully I have not introduced a blunder here:
Code: Select all
; my closing IRQ to avoid keyboard scan
pla
tay
pla
tax
pla
jmp $eb15
The KERNAL ISR already has saved A, X, Y on stack before your own routine at ($0314) is called (see $FF72 as vectored to by the hardware IRQ vector in ROM at $FFFE!), so you don't need to stack them on your own. If you remove that supposed redundancy from your IRQ wedge, you can also omit the PLA/TAY/PLA/TAX/PLA incantation from your IRQ exit, as $EB15 already does this on its own, with the already stacked register contents.