Mitsubishi DS5000TK, DS907x SIP manual Ret, 157

USER'S GUIDE

OPEN:	LCALL	CLOSE	;Make sure it is closed.
	MOV	B,#4	;Set pattern period	count.
	MOV	A,#0C5H	;Load first byte of	pattern.
OPENA:	LCALL	WBYTE	;Send out the byte.
	XRL	A,#0FFH	;Generate next pattern byte.
	LCALL	WBYTE	;Send out the byte.
	SWAP	A	;Generate next pattern byte.
	DJNZ	B,OPENA	;Repeat until 8 bytes sent.
	RET		;Return.

;

;********************************

;*** SUBROUTINE TO CLOSE THE RTC ;********************************

;

;This subroutine insures that the registers of the timekeeper

;are closed by executing 9 successive reads of the date and time

;registers. The subroutine returns with both the accumulator

;and the B register modified.

;
CLOSE:	MOV	B,#9	;Set up		to read 9 bytes.
CLOSEA:	LCALL	RBYTE	;Read	a	byte.
	DJNZ	B,CLOSEA	;Loop	for 9 byte reads.
	RET		;Return.

;

;***********************************

;*** SUBROUTINE TO READ A DATA BYTE ;***********************************

;

;This subroutine performs a ªcontext switch: to the CE2 data

;space and then reads one byte from the timekeeping device.

;Then it switches back to the CE1 data space and returns

;the byte read in the accumulator, with all other registers

;unchanged.

;
RBYTE:	PUSH	DPL	;Save the data
	PUSH	DPH	; pointer on stack.
	PUSH	MCON	;Save MCON register.
	ORL	MCON,#4	;Switch to CE2.
	PUSH	B	;Save the B register.
	MOV	DPL,#4	;Set up for data input.
	MOV	DPH,#0	;Set high address byte.
	MOV	B,#8	;Set the bit count.
LI:	PUSH	ACC	;Save the accumulator.
	MOVX	A,@DPTR	;Input the data bit from the RTC into
			; ACC.7.
	RLC	A	;Move it to carry.
	POP	ACC	;Get the accumulator.
	RRC	A	;Save the data bit.
	DJNZ	B,LI	;Loop for a whole byte.
	POP	B	;Restore the B register.
	POP	MCON	;Restore the MCON register.
			050396 156/173

157