;PROGRAM NAME S2.ASM
;TEST SERIAL OUTPUT PORT SIMULATION
;
BUZZER  REG     P3.4
LED     REG     P3.7
;
RESET   MOV     R0,#00H
        DJNZ    R0,$
        CLR     BUZZER
        CLR     BUZZER
;
        SETB    P3.0            ;RXD=1
        SETB    P3.1            ;TXD=1
AGAIN   MOV     R7,#81H
        MOV     R6,#AAH
        LCALL   SERIAL_OUT
        LCALL   DELAY
        SJMP    AGAIN
;
SERIAL_OUT
        CLR     C
        MOV     A,R7
        LCALL   SENDBYT
        NOP
        NOP
        NOP
        CLR     C
        MOV     A,R6
        LCALL   SENDBYT
        RET
;
SENDBYT MOV     R0,#08H
SBIT    RRC     A
        JC      OUT1
OUT0    LCALL   OUTLO
        SJMP    SENDNXT
OUT1    LCALL   OUTHI
SENDNXT DJNZ    R0,SBIT
        RET
;
OUTLO   CLR     P3.0
        LCALL   PULSE
        RET
;
OUTHI   SETB    P3.0
        LCALL   PULSE
        RET
;
PULSE   SETB    P3.1
        CLR     P3.1
        NOP
        NOP
        SETB    P3.1
        RET
;
DELAY   MOV     R0,#0
$1      MOV     R1,#0
        DJNZ    R1,$
        DJNZ    R0,$1
        RET