AY38910: Fix issue with interrupt handling during boot beep

Source/HBIOS/ay38910.asm

@@ -137,10 +137,15 @@ AY_FND:	LD	IY, AY_IDAT		; SETUP FUNCTION TABLE
 	LD	HL, AY_TIMER		; INSTALL TIMER HOOK HANDLER
 	LD	(VEC_TICK + 1), HL
 
+	LD	A, $02			; NOT READY & IN INTERUPT HANDLER
+	LD	(AY_READY), A
+
 #ELSE
  	CALL	LDELAY			; HALF SECOND DELAY
  	LD	E,$00			; SET VOLUME OFF
- 	CALL	AY_SETV			; ON ALL CHANNELS
+	CALL	AY_SETV			; ON ALL CHANNELS
+	LD	A, $01			; READY & NOT IN INTERUPT HANDLER
+	LD	(AY_READY), A
 
 #ENDIF
 ;
@@ -159,6 +164,8 @@ AY_TIMER:
 
 	LD	E,$00			; SET VOLUME OFF
 	CALL	AY_SETV			; ON ALL CHANNELS
+	LD	A, $01			; READY & NOT IN INTERUPT HANDLER
+	LD	(AY_READY), A
 
 AY_TIMER1:
 	JP	0			; OVERWRITTEN WITH NEXT HANDLER
@@ -174,8 +181,16 @@ AY_TIMTIK	.DB	0		; COUNT DOWN TO FINISH BOOT BEEP
 ;
 AY_INIT:
 	LD	DE,(AY_R7ENAB*256)+$F8	; SET MIXER CONTROL / IO ENABLE.  $F8 - 11 111 000
-	CALL	AY_WRTPSG		; I/O PORTS = OUTPUT, NOISE CHANNEL C, B, A DISABLE, TONE CHANNEL C, B, A ENABLE
-	RET
+	JP	AY_WRTPSG		; I/O PORTS = OUTPUT, NOISE CHANNEL C, B, A DISABLE, TONE CHANNEL C, B, A ENABLE
+
+AY_CHKREDY:
+	LD	A, (AY_READY)
+	BIT	0, A
+	RET	NZ
+
+	POP	HL			; REMOVE LAST RETURN ADDRESS
+	OR	$FF
+	RET				; RETURN NZ
 ;
 ;======================================================================
 ;	SET VOLUME ALL CHANNELS
@@ -200,7 +215,8 @@ AY_SV:	CALL	AY_WRTPSG		; CYCLING THROUGH ALL CHANNELS
 ;
 AY_RESET:
 	AUDTRACE(AYT_INIT)
-;
+	CALL	AY_CHKREDY		; RETURNS TO OUR CALLER IF NOT READY
+
 	PUSH	DE
 	PUSH	HL
 	CALL	AY_INIT			; SET DEFAULT CHIP CONFIGURATION
@@ -227,6 +243,7 @@ AY_VOLUME:
 	AUDTRACE(AYT_VOL)
 	AUDTRACE_L
 	AUDTRACE_CR
+
 	LD	A,L			; SAVE VOLUME
 	LD	(AY_PENDING_VOLUME), A
 ;
@@ -283,6 +300,8 @@ AY_PLAY:
 	AUDTRACE(AYT_PLAY)
 	AUDTRACE_D
 	AUDTRACE_CR
+	CALL	AY_CHKREDY		; RETURNS TO OUR CALLER IF NOT READY
+
 ;
 	LD	A, (AY_PENDING_PERIOD + 1)	; CHECK THE HIGH BYTE OF THE PERIOD
 	INC	A
@@ -390,6 +409,21 @@ AY_QUERY_DEV:
 	LD	DE, (AY_RSEL*256)+AY_RDAT	; AND ADDRESS AND DATA PORT
 	XOR	A
 	RET
+
+AY_DI:
+	LD	A, (AY_READY)
+	BIT	1, A
+	RET	NZ
+	HB_DI
+	RET
+
+AY_EI:
+	LD	A, (AY_READY)
+	BIT	1, A
+	RET	NZ
+	HB_EI
+	RET
+
 ;
 ;======================================================================
 ;
@@ -399,7 +433,7 @@ AY_QUERY_DEV:
 ;======================================================================
 ;
 AY_WRTPSG:
-	HB_DI
+	CALL	AY_DI
 #IF (SBCV2004)
 	LD	A,8			; SBC-V2-004 CHANGE
 	OUT	(112),A			; TO HALF CLOCK SPEED
@@ -422,8 +456,7 @@ AY_WRTPSG:
 	LD	A,0			; SBC-V2-004 CHANGE TO
 	OUT	(112),A			; NORMAL CLOCK SPEED
 #ENDIF
-	HB_EI
-	RET
+	JP	AY_EI
 
 ;
 ;======================================================================
@@ -431,7 +464,7 @@ AY_WRTPSG:
 ;	READ FROM REGISTER D AND RETURN WITH RESULT IN E
 ;
 AY_RDPSG:
-	HB_DI
+	CALL	AY_DI
 #IF (SBCV2004)
 	LD	A,8			; SBC-V2-004 CHANGE
 	OUT	(112),A			; TO HALF CLOCK SPEED
@@ -454,13 +487,14 @@ AY_RDPSG:
 	LD	A,0			; SBC-V2-004 CHANGE TO
 	OUT	(112),A			; NORMAL CLOCK SPEED
 #ENDIF
-	HB_EI
-	RET
+	JP	AY_EI
 ;
 ;======================================================================
 ;
 AY_PENDING_PERIOD	.DW	0	; PENDING PERIOD (12 BITS)	; ORDER
 AY_PENDING_VOLUME	.DB	0	; PENDING VOL (8 BITS)		; SIGNIFICANT
+AY_READY		.DB	0	; BIT 0 -> NZ DRIVER IS READY TO RECEIVE PLAY COMMAND
+					; BIT 1 -> NZ EXECUTING WITHIN TIMER HANDLER = DO NOT DIS/ENABLE INT
 ;
 #IF AUDIOTRACE
 AYT_INIT		.DB	"\r\nAY_INIT\r\n$"