ORG 09000H

	PUSH HL
	PUSH AF
		LD HL,0FFFEH	;previous 10 key state
		LD A,(HL)
		INC A
		JR NZ,TEN_KEY	;10 key start
		
FULL_KEY:
		IN A,(0)		;check 10 key input
		INC A
		JR NZ,KEY_OFF	;10 key start -> stop song

		IN A,(6)		;check full key input
		LD HL,0FFFFH	;previous full key state
		CP (HL)
		LD (HL),A		;update previous full key state
		JR Z,KEY_ON		;same full key
		INC A
		JR Z,KEY_ON		;full key off
		JR KEY_OFF		;other key on

TEN_KEY:
		IN A,(0)		;check 10 key input
		INC A
		JR Z,KEY_OFF	;10 key off
		JR KEY_ON		;10 key on

KEY_OFF:
	POP AF
	POP HL
	SCF			;stop song
	RET

KEY_ON:
	POP AF
	POP HL
	SCF
	CCF			;continue
	RET