Add VDA Read Character function

For your consideration. Seems to work.

Source/Doc/Architecture.md

@@ -1368,6 +1368,25 @@ codes as described at the start of this section.
 
 `\clearpage`{=latex}
 
+### Function 0x4F -- Read a character at current video position (VDARDC)
+
+| _Entry Parameters_
+|       B: 0x4F
+|       C: Video Device Unit ID
+
+| _Exit Results_
+|       A: Status (0=OK, else error)
+|       E: Character
+|       B: Character Color Code
+|       C: Character Attribute Code
+
+Read a character from the current cursor position including it's colour
+and attributes. If the display does not support colours or attributes
+then return colour white on black and no attributes. If the device does
+not support the ability to read a character, return error status
+
+`\clearpage`{=latex}
+
 Sound (SND)
 ------------
 

Source/HBIOS/cvdu.asm

@@ -94,6 +94,7 @@ CVDU_FNTBL:
 	.DW	KBD_STAT
 	.DW	KBD_FLUSH
 	.DW	KBD_READ
+	.DW	CVDU_VDARDC
 #IF (($ - CVDU_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID CVDU FUNCTION TABLE ***\n"
 	!!!!!
@@ -219,6 +220,15 @@ CVDU_VDASCR1:
 	POP	DE		; RECOVER E
 	INC	E		; INCREMENT IT
 	JR	CVDU_VDASCR	; LOOP
+
+;----------------------------------------------------------------------
+; READ VALUE AT CURRENT VDU BUFFER POSITION
+; RETURN E = CHARACTER, B = COLOUR, C = ATTRIBUTES
+;----------------------------------------------------------------------
+
+CVDU_VDARDC:
+	OR	$FF		; UNSUPPORTED FUNCTION
+	RET
 ;
 ;======================================================================
 ; CVDU DRIVER - PRIVATE DRIVER FUNCTIONS

Source/HBIOS/hbios.asm

@@ -191,13 +191,13 @@ RTCDEF		.SET	RTCDEF | %00000001	; SC128 I2C SCL BIT
 #IF (CPUSPDDEF==SPD_HIGH)
 RTCDEF		.SET	RTCDEF | %00001000	; DEFAULT SPEED HIGH
 #ELSE
-RTCDEF		.SET	RTCDEF | %00000000	; DEFAULT SPEED LOW
+RTCDEF		.SET	RTCDEF & %11110111	; DEFAULT SPEED LOW
 #ENDIF
 #ENDIF
 ;
 #IF (!(CPUSPDCAP==SPD_FIXED) & (PLATFORM==PLT_SBC))
 #IF (CPUSPDDEF==SPD_HIGH)
-RTCDEF		.SET	RTCDEF | %00000000	; DEFAULT SPEED HIGH
+RTCDEF		.SET	RTCDEF & %11110111	; DEFAULT SPEED HIGH
 #ELSE
 RTCDEF		.SET	RTCDEF | %00001000	; DEFAULT SPEED LOW
 #ENDIF
@@ -3202,7 +3202,7 @@ VDA_ADDENT:
 ;	WORD	DRIVER FUNCTION TABLE ADDRESS
 ;	WORD	UNIT SPECIFIC DATA (TYPICALLY A DEVICE INSTANCE DATA ADDRESS)
 ;
-VDA_FNCNT	.EQU	15		; NUMBER OF VDA FUNCS (FOR RANGE CHECK)
+VDA_FNCNT	.EQU	16		; NUMBER OF VDA FUNCS (FOR RANGE CHECK)
 VDA_MAX		.EQU	16		; UP TO 16 UNITS
 VDA_SIZ		.EQU	VDA_MAX * 4	; EACH ENTRY IS 4 BYTES
 ;
@@ -6231,7 +6231,6 @@ HB_SECS		.FILL	4,0		; 32 BIT SECONDS COUNTER
 ;
 HB_CPUTYPE	.DB	0		; 0=Z80, 1=80180, 2=SL1960, 3=ASCI BRG
 ;
-;RTCVAL		.DB	RTCDEF		; SHADOW VALUE FOR RTC LATCH PORT
 IOPRVAL		.DW	0		; TEMP STORAGE FOR IOPR
 ;
 HB_BATCOND	.DB	0		; BATTERY CONDITION (0=LOW, 1=OK)

Source/HBIOS/tms.asm

@@ -209,6 +209,7 @@ TMS_FNTBL:
 	.DW	TMS_READ
 #ENDIF
 #ENDIF
+	.DW	TMS_VDARDC
 #IF (($ - TMS_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID TMS FUNCTION TABLE ***\n"
 	!!!!!
@@ -345,6 +346,15 @@ TMS_VDASCR2:
 	XOR	A
 	RET
 
+;----------------------------------------------------------------------
+; READ VALUE AT CURRENT VDU BUFFER POSITION
+; RETURN E = CHARACTER, B = COLOUR, C = ATTRIBUTES
+;----------------------------------------------------------------------
+
+TMS_VDARDC:
+	OR	$FF		; UNSUPPORTED FUNCTION
+	RET
+
 ; DUMMY FUNCTIONS BELOW BECAUSE SCG BOARD HAS NO
 ; KEYBOARD INTERFACE
 

Source/HBIOS/vdu.asm

@@ -148,11 +148,12 @@ VDU_FNTBL:
 	.DW	PPK_STAT
 	.DW	PPK_FLUSH
 	.DW	PPK_READ
+	.DW	VDU_VDARDC
 #IF (($ - VDU_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID VDU FUNCTION TABLE ***\n"
 	!!!!!
 #ENDIF
-
+;
 VDU_VDAINI:
 	; RESET VDA
 	; CURRENTLY IGNORES VIDEO MODE AND BITMAP DATA
@@ -258,6 +259,28 @@ VDU_VDASCR1:
 	INC	E		; INCREMENT IT
 	JR	VDU_VDASCR	; LOOP
 ;
+;----------------------------------------------------------------------
+; READ VALUE AT CURRENT VDU BUFFER POSITION
+; RETURN E = CHARACTER, B = COLOUR, C = ATTRIBUTES
+;----------------------------------------------------------------------
+;
+VDU_VDARDC:
+	LD	C,18		; SET SOURCE ADDRESS IN VDU (HL)
+	CALL	VDU_WRREGX	; DO IT
+
+   	LD 	A,31		; PREP VDU FOR DATA R/W
+    	OUT 	(VDU_REG),A	; DO IT
+
+	CALL	VDU_WAITRDY	; WAIT FOR VDU TO BE READY
+
+	LD	C,VDU_RAMRD	; LOAD C WITH VDU READ REGISTER
+	IN	E,(C)
+
+	LD	B,$F0		; WHITE FG. BLACK BG
+	LD	C,$00		; NO ATTRIBUTES
+	XOR	A
+	RET
+;
 ;======================================================================
 ; VDU DRIVER - PRIVATE DRIVER FUNCTIONS
 ;======================================================================

Source/HBIOS/vga.asm

@@ -161,6 +161,7 @@ VGA_FNTBL:
 	.DW	KBD_STAT
 	.DW	KBD_FLUSH
 	.DW	KBD_READ
+	.DW	VGA_VDARDC
 #IF (($ - VGA_FNTBL) != (VDA_FNCNT * 2))
 	.ECHO	"*** INVALID VGA FUNCTION TABLE ***\n"
 	!!!!!
@@ -313,6 +314,15 @@ VGA_VDASCR1:
 	POP	DE		; RECOVER E
 	INC	E		; INCREMENT IT
 	JR	VGA_VDASCR	; LOOP
+
+;----------------------------------------------------------------------
+; READ VALUE AT CURRENT VDU BUFFER POSITION
+; RETURN E = CHARACTER, B = COLOUR, C = ATTRIBUTES
+;----------------------------------------------------------------------
+
+VGA_VDARDC:
+	OR	$FF		; UNSUPPORTED FUNCTION
+	RET
 ;
 ;======================================================================
 ; VGA DRIVER - PRIVATE DRIVER FUNCTIONS