; OPUS I THE TRS-80 CONCERTO
 ;
.org	0000h
		LD	SP,	0080h		; ADDED FOR TESTING PURPOSES.

START:	LD	IX,	TABLE		; START OF MUSIC TABLE.
CONT1:	LD	C,	(IX)		; DURATION.
		LD	A,	C			; MOVE TO A FOR TEST.
		OR	A				; TEST FOR 0.
LOOP:	JP	Z,	LOOP		; LOOP HERE ON DONE.
CONT2:	LD	B,	(IX +1)		; GET DELAY COUNT.
		LD	A,	1
		OUT	(0FFh),	A		; TURN ON 1/2 CYCLE.
LOOP1:	DJNZ	LOOP1		; DELAY FOR FREQUENCY.
		LD	B,	(IX +1)		; GET DELAY AGAIN.
		LD	A,	2
		OUT	(0FFh),	A		; TURN ON OTHER 1/2 CYCLE.
LOOP2:	DJNZ	LOOP2		; DELAY FOR FREQUENCY.
LOOP3:	DEC	C				; DECREMENT DURATION.
		JP	NZ,	CONT2		; GO IF NOT DONE.
		INC	IX				; POINT TO NEXT NOTE.
		INC IX
		LD	BC,	-1			; INCREMENT VALUE.
		LD	HL,	30h			; INITIAL DELAY VALUE.
LOOP4:	ADD	HL,	BC			; DELAY FOR INTERVAL BETWEEN NOTES.
		JP	C,	LOOP4
		JP	CONT1			; CONTINUE.
TABLE:	.DB	90A0h			; TABLE OF NOTES.
		.DB	0A23Fh			; EACH ENTRY IS MADE UP OF TWO BYTES.
		.DB	0AC5Ch			; FIRST BYTE IS DURATION OF NOTE.
		.DB	9060h			; SECOND BYTES IS FREQUENCY VALUE.
		.DB	90A0h
		.DB 9040h
		.DB 8070h
		.DB 90F0h
		.DB	0A25Dh
		.DB 0AD5Bh
		.DB 9060h
		.DB 6BE0h
		.DB 5F48h
		.DB 54FFh
		.DB	0				; TERMINATOR.
.END