// execute an opcode in fast memory

// write a long jump instruction to fast memory
// check if the long jump is actually there (by reading it)
// and execute it

	*=$1000

	sei
	
	; native mode
	clc
	xce
	; index 16bit
	rep #%00010000
	.xl

	; setup return jmp
	lda #$5c	; JMP absolute long (interbank)
	sta @$080000
	lda #<retjmp	; low byte return addr
	sta @$080001
	lda #>retjmp	; page return addr
	sta @$080002
	lda #0		; bank return addr
	sta @$080003

	; copy the jump back to $2000. if unsure, uncomment the
	; long jump below and first check if the memory actually contains 
	; the return jump
	ldx #3
l1
	lda @$080000,x
	sta $2000,x
	dex
	bpl l1

	; execute far jmp with direct jmp back to retjmp
	jmp @$080000

retjmp
	; emulation mode
	.xs
	sec
	xce
	cli
	rts