______________________________________________________________
;....DAC.ASM...COMPILER ISMETALINK 8051 CROSS ASSEMBLER
$MOD812


PORT2		DATA	0AH	;SFR REGISTER FOR PORT2
DAC_VALUE	DATA	40H	;DAC VALUE
DAC_ADDR	DATA	42H     ;DAC ADDRESS (0-7)
LOOPCOUNT	DATA	44H     ;COUNT LOOPS
LED		EQU	P3.4     ;IS LED


                        JMP LD_8802
;............................................................
CSEG
     		ORG	 0003h    	; (INT0 ISR)
;...........................................................

              

		ORG    	100H	       	;ARBITRAY START
                             
LD_8802:
; configure the UART ADuC812
    MOV     SCON,#52h  ; configure UART for 9600baud..
    MOV     TMOD,#20h  ; ..assuming 11.0592MHz crystal
    MOV     TH1,#-3
    SETB    TR1       	; ok this works


;...IS THIS THE RIGHT PLACE FOR THIS?.....................		
    JNB     RI,$        ; Recive serial data
    MOV     40H,SBUF    ; Store data in IN MEMORY

    JNB     RI,$        ; Recive serial data
    MOV     42H,SBUF    ; Store data in IN MEMORY
;.........................................................

		ORL	P2,#11110000B 	;SET CLK,CS,SHDN HIGH
		CLR	P2.5		;SET CHIP SELECT LOW
		MOV	LOOPCOUNT,#4	;ADDRESS IS 4 BITS
		MOV	A,DAC_ADDR	;GET DAC ADDRESS
		RR	A		;ROTATE THE DAC
		RR	A		;ADDRESS TO MOST
		RR	A		;SIGNIFCANT BIT (MSB)
		RR	A
		ACALL	SEND_SERIAL	;SEND THE ADDRESS
		MOV	LOOPCOUNT,#8	;DO 8 BIT OF DATA
		MOV	A,DAC_VALUE
		ACALL	SEND_SERIAL	;SEND THE DATA
		SETB	P2.5		;SET CS HIGH


SEND_SERIAL:	RLC	A	;MOVE NEXT BIT TO CARRY
                CPL	LED	;BLINK LED
                MOV	P2.7,C	;MOVE DATA TO SDI
                CLR 	P2.6	;PULSE THE
                SETB	P2.6	;CLK INPUT
                DJNZ	LOOPCOUNT,SEND_SERIAL ;LOOP IF NOT DONE
                RET				;DONE
                END