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, sequence according to Compute's Mapping the Commodore 64, page 73
	pha
	txa
	pha
	tya
	pha

	;; Check if caused by BRK

	;; XXX disabled for now - resets Duotris game, unknown why
	; tsx
	; lda $0104, x ; get the pre-interrupt processor state
	; and #$10
	; bne irq_handler_brk

	;; Not caused by BRK - call interrupt routine (only if initialised)
	lda CINV
	ora CINV+1
	beq +
	jmp (CINV)
*
	;; Vector not initialized - call default interrupt routine
	jmp default_irq_handler

irq_handler_brk:

	;; Interrupt caused by BRK
	jmp (CBINV)