nmi_handler:

	sei ;; don't allow IRQ to interfere, see https://www.c64-wiki.com/wiki/Interrupt

	;; Call interrupt routine (only if initialised)
	pha
	lda NMINV
	ora NMINV+1
	beq +
	pla
	jmp (NMINV)
*
	;; Vector not initialized - call default interrupt routine
	pla
	jmp default_nmi_handler