SN76489: refactor - remove custom div16 function - use common hbios util div16 function

Source/HBIOS/sn76489.asm

@@ -5,6 +5,9 @@
 ;======================================================================
 ;
 ; TODO:
+; 1. PROVIDE SUPPORT FOR NOISE CHANNEL
+; 2. FOR PERIOD SET, MAP 400 TO 0 AND RETURN ERROR FOR 000
+; 3. DOES THIS WORK FOR FASTER CPUS? ONLY BEEN TEST ON A Z80 7MHZ UNIT
 ;
 ;======================================================================
 ; CONSTANTS
@@ -104,13 +107,10 @@ SN7_NOTE:
 	AUDTRACE_HL
 	AUDTRACE_CR
 
-	LD	B, H
-	LD	C, L
 	LD	DE, 48
-
-	CALL	_DIV16
+	CALL	DIV16
 					; BC IS OCTAVE COUNT
-					; HL is NOTE WITIN ACTAVE
+					; HL is NOTE WITIN OCTAVE
 	ADD	HL, HL
 	LD	DE, SN7NOTETBL
 	ADD	HL, DE
@@ -129,55 +129,21 @@ SN7_NOTE1:
 	JR	SN7_NOTE1
 
 SN7_NOTE2:
-	LD	A, L
+	LD	A, L			; IF WE GENERATE ZERO - RETURN ERROR
 	OR	H
-	JR	NZ, SN7_PERIOD
+	JR	NZ, SN7_PERIOD		; OTHERWISE APPLY THE CALCULATED PERIOD
 
 	LD	H, $FF
 	LD	L, $FF
 	JR	SN7_PERIOD
 
-; Divide 16-bit values (with 16-bit result)
-; In: Divide BC by divider DE
-; Out: BC = result, HL = rest
-;
-_DIV16:
-	LD	HL, 0
-	LD	A, B
-	LD	B, 8
-DIV16_LOOP1:
-	RLA
-	ADC	HL, HL
-	SBC	HL, DE
-	JR	NC, DIV16_NOADD1
-	ADD	HL, DE
-DIV16_NOADD1:
-	DJNZ	DIV16_LOOP1
-	RLA
-	CPL
-	LD	B, A
-	LD	A, C
-	LD	C, B
-	LD	B, 8
-DIV16_LOOP2:
-	RLA
-	ADC	HL, HL
-	SBC	HL, DE
-	JR	NC, DIV16_NOADD2
-	ADD	HL, DE
-DIV16_NOADD2:
-	DJNZ	DIV16_LOOP2
-	RLA
-	CPL
-	LD	B, C
-	LD	C, A
-	RET
-
 SN7_PERIOD:
 	AUDTRACE(SNT_PERIOD)
 	AUDTRACE_HL
 	AUDTRACE_CR
 
+	; TODO: MAKE ZERO BE AN INVALID VALUE (USE 400) TO INDICATE LOWEST NOTE
+	; NEED TO UPDATE TUNE.ASM TO SUPPORT THIS?
 	; LD	A, H			; IF ZERO - ERROR
 	; OR	L
 	; JR	Z, SN7_QUERY_PERIOD1
@@ -398,10 +364,11 @@ SNT_PLAY		.DB	"\r\nSN7_PLAY CH: $"
 SNT_REGWR		.DB	"\r\nOUT SN76489, $"
 #ENDIF
 
-; THE FREQUENCY BY QUARTER TONE STARTING AT A0#
-; OCATVE 0 - not suported by this driver
-; FIRST PLAYABLE NOTE WILL BE $2E - 2 quater tones below a1#
-; A1# is $30
+; THE FREQUENCY BY QUARTER TONE STARTING AT A0# OCATVE 0
+; USED TO MAP EACH OCTAVE (DIV BY 2 TO JUMP AN OCTAVE UP)
+; FIRST PLAYABLE NOTE WILL BE $2E
+; ASSUMING A CLOCK OF 1843200 THIS MAPS TO
+; 2 QUATER TONES BELOW A1#, WITH A1# AT $30
 
 SN7NOTETBL:
 	.DW	SN7RATIO / 2913
@@ -454,9 +421,3 @@ SN7NOTETBL:
 	.DW	SN7RATIO / 5743
 
 SIZ_SN7NOTETBL	.EQU	$ - SN7NOTETBL
-		.ECHO	"SN76489 approx "
-		.ECHO	SIZ_SN7NOTETBL / 2 / 4 /12
-		.ECHO	" Octaves.  Last note index supported: "
-
-		.ECHO SIZ_SN7NOTETBL / 2
-		.ECHO "\n"