32 lines
810 B
ArmAsm
32 lines
810 B
ArmAsm
irq_handler:
|
|
;; The IRQ is a commonly messed with thing on the C64,
|
|
;; so we need to handle entry points that are commonly
|
|
;; relied upon, including:
|
|
;; $EA31 - Standard IRQ routine
|
|
;; $EA61 - Check keyboard, but don't update timer? https://github.com/cc65/cc65/issues/324
|
|
;; $EA81 - https://www.lemon64.com/forum/viewtopic.php?t=2112&sid=6ea01982b26da69783120a7923ca46fb
|
|
;; Also the $0314 vector is widely used (e.g., https://www.lemon64.com/forum/viewtopic.php?t=2112&sid=6ea01982b26da69783120a7923ca46fb)
|
|
|
|
;; Save registers
|
|
pha
|
|
txa
|
|
pha
|
|
tya
|
|
pha
|
|
|
|
;; Acknowledge CIA interrupt
|
|
lda $dc0d
|
|
|
|
;; Call interrupt routine
|
|
;; (but only if initialised)
|
|
lda $0314
|
|
ora $0315
|
|
beq default_irq_handler
|
|
jmp ($0314)
|
|
default_irq_handler:
|
|
|
|
jsr blink_cursor
|
|
jsr scan_keyboard
|
|
|
|
jmp return_from_interrupt
|