;;
;; Checks whether device number (in .A) is a correct IEC device number
;;
;; Preserves .A, .X and .Y
;;

iec_check_devnum:
	;; 0, 1, 2, or 3 are illegal - reserved for non-IEC devices on Commodore
	cmp #$04
	bcs +
	;; FALLTROUGH
iec_check_devnum_failed:
	sec ; indicate non-IEC device
	rts
*
	;; 31 and above are illegal too, due to IEC command encoding scheme,
	;; see https://www.pagetable.com/?p=1031
	cmp #$1F
	bcs iec_check_devnum_failed
	;; Carry is clear here - indicates IEC device
	rts