Update cvdu.asm

- Improves compatibility with high speed CPUs.
wwarthen · Jan 8, 2025 · 8a16b85 · 8a16b85
1 parent a27f247
commit 8a16b85
Showing 1 changed file with 22 additions and 3 deletions.
diff --git a/Source/HBIOS/cvdu.asm b/Source/HBIOS/cvdu.asm
@@ -10,7 +10,6 @@
 ;   - IMPLEMENT SET CURSOR STYLE (VDASCS) FUNCTION
 ;   - IMPLEMENT ALTERNATE DISPLAY MODES?
 ;   - IMPLEMENT DYNAMIC READ/WRITE OF CHARACTER BITMAP DATA?
-;   - IMPLEMENT TIMEOUT ON PROBE
 ;
 ;======================================================================
 ; CVDU DRIVER - CONSTANTS
@@ -295,6 +294,16 @@ CVDU_WR:
 	PUSH	AF			; SAVE VALUE TO WRITE
 	LD	A,C			; SET A TO CVDU REGISTER TO SELECT
 	OUT	(CVDU_REG),A		; WRITE IT TO SELECT THE REGISTER
+;
+#IF (CPUMHZ > 8)
+	; FASTER CPUS NEED A SMALL DELAY BEFORE THEY CAN START
+	; POLLING THE CVDU STATUS.  THIS IS NOT IDEAL BECAUSE THE
+	; CONDITIONAL IS BASED ON THE CPU CONFIG SPEED, NOT THE
+	; DYNAMIC CPU SPEED.
+	NOP
+	NOP
+#ENDIF
+;
 CVDU_WR1:
 	IN	A,(CVDU_STAT)		; GET CVDU STATUS
 	BIT	7,A			; CHECK BIT 7
@@ -320,6 +329,16 @@ CVDU_WRX:
 CVDU_RD:
 	LD	A,C			; SET A TO CVDU REGISTER TO SELECT
 	OUT	(CVDU_REG),A		; WRITE IT TO SELECT THE REGISTER
+;
+#IF (CPUMHZ > 8)
+	; FASTER CPUS NEED A SMALL DELAY BEFORE THEY CAN START
+	; POLLING THE CVDU STATUS.  THIS IS NOT IDEAL BECAUSE THE
+	; CONDITIONAL IS BASED ON THE CPU CONFIG SPEED, NOT THE
+	; DYNAMIC CPU SPEED.
+	NOP
+	NOP
+#ENDIF
+;
 CVDU_RD1:
 	IN	A,(CVDU_STAT)		; GET CVDU STATUS
 	BIT	7,A			; CHECK BIT 7
@@ -350,13 +369,13 @@ CVDU_PROBE1:
 	LD	A,(HL)				; BYTE
 	INC	HL
 	OUT	(C),A				; WRITE IT
-	LD	DE,25
+	LD	DE,50
 	CALL	VDELAY
 	DJNZ	CVDU_PROBE1
 ;
 	IN	A,(CVDU_DATA)
 	LD	C,A
-	LD	DE,25
+	LD	DE,50
 	CALL	VDELAY
 	IN	A,(CVDU_DATA)
 	CPL