Cleanup of DS12RTC Driver

- Offset NVRAM register access by $60 to avoid collisions with IBM PC CMOS usage.
- Wrap register accesses in DI/EI.  The DS1288x requires no interrupts between the register selection and the data r/w.
- Minor comment improvements.

Source/HBIOS/ds12rtc.asm

@@ -43,6 +43,11 @@
 ;  | $0D | VRT   | 0     | 0     | 0     | 0     | 0     | 0     | 0     |
 ;  +-----+-------+-------+-------+-------+-------+-------+-------+-------+
 ;
+; NOTE: THE IBM PC CMOS USES REGISTER ADDRESSES UP TO $5F.  THIS RTC
+; IS SOMETIMES USED IN SYSTEMS THAT HAVE A X86 BOARD, SO WE AVOID ANY
+; CONFLICT BY OFFSETTING OUR REGISTER INDEXES BY $60.  THIS MEANS WE
+; MAP REQUESTS FOR $00-$1F TO NVRAM REGISTERS $60-$7F.
+;
 DS12RTC_IO	.EQU	$70
 DS12RTC_SEL	.EQU	DS12RTC_IO + 0
 DS12RTC_DATA	.EQU	DS12RTC_IO + 1
@@ -197,7 +202,7 @@ DS12RTC_SETTIM:
 ;
 DS12RTC_GETBYT:
 	LD	A,C			; INDEX TO ACCUM
-	ADD	A,$0E			; RAM STARTS AT INDEX $0E
+	ADD	A,$60			; WE USE NVRAM STARTING AT $60
 	LD	C,A			; INDEX BACK TO C
 	CALL	DS12RTC_RDREG		; GET THE VALUE
 	LD	E,A			; PUT IN E TO RETURN
@@ -210,7 +215,7 @@ DS12RTC_GETBYT:
 ;
 DS12RTC_SETBYT:
 	LD	A,C			; INDEX TO ACCUM
-	ADD	A,$0E			; RAM STARTS AT INDEX $0E
+	ADD	A,$60			; WE USE NVRAM STARTING AT $60
 	LD	C,A			; INDEX BACK TO C
 	LD	A,E			; PUT VALUE IN A
 	CALL	DS12RTC_WRREG		; WRITE IT
@@ -283,25 +288,25 @@ DS12RTC_WRCLK:
 	LD	E,L			; ... IN CASE OF RESTART
 	LD	C,$09			; START WITH YEAR REG
 	CALL	DS12RTC_WRCLK1		; DO YEAR (REG $09)
-	JR	NZ,DS12RTC_WRCLK	; RESTART IF SO
+	JR	NZ,DS12RTC_WRCLK	; RESTART IF UIP DETECTED
 	CALL	DS12RTC_WRCLK1		; DO MONTH (REG $08)
-	JR	NZ,DS12RTC_WRCLK	; RESTART IF SO
+	JR	NZ,DS12RTC_WRCLK	; RESTART IF UIP DETECTED
 	CALL	DS12RTC_WRCLK1		; DO DAY OF MONTH (REG $07)
-	JR	NZ,DS12RTC_WRCLK	; RESTART IF SO
+	JR	NZ,DS12RTC_WRCLK	; RESTART IF UIP DETECTED
 	DEC	C			; SKIP DAY OF WEEK (REG $06)
 	DEC	C			; SKIP HOURS ALARM (REG $05)
 	CALL	DS12RTC_WRCLK1		; DO HOUR (REG $04)
-	JR	NZ,DS12RTC_WRCLK	; RESTART IF SO
+	JR	NZ,DS12RTC_WRCLK	; RESTART IF UIP DETECTED
 	DEC	C			; SKIP MINUTES ALARM (REG $03)
 	CALL	DS12RTC_WRCLK1		; DO MINUTES (REG $02)
-	JR	NZ,DS12RTC_WRCLK	; RESTART IF SO
+	JR	NZ,DS12RTC_WRCLK	; RESTART IF UIP DETECTED
 	DEC	C			; SKIP SECONDS ALARM (REG $01)
 	CALL	DS12RTC_WRCLK1		; DO SECONDS (REG $00)
 ;
 	XOR	A			; SIGNAL SUCCESS
 	RET				; DONE
 ;	
-DS12RTC_WRCLK1:				; 108TS
+DS12RTC_WRCLK1:
 	LD	A,(DE)			; GET VALUE
 	CALL	DS12RTC_WRREG		; WRITE IT
 	INC	DE			; BUMP BUF PTR
@@ -339,22 +344,26 @@ DS12RTC_INITDEV:
 ;   C=REGISTER
 ;   A=VALUE
 ;
-DS12RTC_RDREG:				; 43TS
+DS12RTC_RDREG:
+	HB_DI				; NO INTS BETWEEN REG SEL AND DATA
 	LD	A,C			; REGSITER TO A
 	OUT	(DS12RTC_SEL),A		; SELECT IT
 	IN	A,(DS12RTC_DATA)	; GET REG VALUE
+	HB_EI				; RESTORE INTS
 	RET				; DONE
 ;
 ; WRITE REGSITER
 ;   C=REGSITER
 ;   A=VALUE
 ;
-DS12RTC_WRREG:				; 64TS
+DS12RTC_WRREG:
+	HB_DI				; NO INTS BETWEEN REG SEL AND DATA
 	PUSH	AF			; SAVE VALUE TO WRITE
 	LD	A,C			; REGSITER TO A
 	OUT	(DS12RTC_SEL),A		; SELECT IT
 	POP	AF			; RECOVER VALUE TO WRITE
 	OUT	(DS12RTC_DATA),A	; GET REG VALUE
+	HB_EI				; RESTORE INTS
 	RET				; DONE
 ;
 ; CHECK FOR UPDATE IN PROGRESS
@@ -377,4 +386,4 @@ DS12RTC_UIP:
 ; DS12RTC_TIMBUF IS DRIVER'S INTERNAL CLOCK DATA BUFFER
 ;
 DS12RTC_TIMBUF	.FILL	6,0		; 6 BYTES FOR GETTIM, YYMMDDHHMMSS
-DS12RTC_TIMDEF	.DB	$00,$01,$01,$00,$00,$00
+DS12RTC_TIMDEF	.DB	$00,$01,$01,$00,$00,$00	; DEFAULT DATE/TIME