GETCMD:
	MOV A,#0
	ACALL CHAR_IN ;WAIT FOR PC TO SENT A CHARACTER
		      ;NOW PROCESS
      CJNE A,#'1',NOT1 ;IF ITS NOT 1 THEN CHECK NEXT POSSIBILITY
      ACALL SUB1 ;ELSE ITS 1
NOT1: CJNE A,#'2',NOT2 ;IF ITS NOT 2 THEN CHECK NEXT POSSIBILITY
ACALL SUB2 ;ELSE ITS 2
NOT2: CJNE A,#'3',NOT3 ;IF ITS NOT 3 THEN CHECK NEXT POSSIBILITY
      ACALL SUB3 ;ELSE ITS 3
NOT3: CJNE A,#'4',NOT4 ;IF ITS NOT 4 THEN CHECK NEXT POSSIBILITY
      ACALL SUB4 ;ELSE ITS 4
NOT4:
ENDCHK:
RET


SUB1: MOV A, #01h                  
      MOV P2, A ;TURN ON PORT2 PIN 0
      ACALL DELAY
      MOV P2, #00h
      RET
		  
SUB2: MOV A, #02h                  
      MOV P2, A ;TURN ON PORT2 PIN 1
      ACALL DELAY
      MOV P2, #00h
      RET
		  
SUB3: MOV A, #04h                  
      MOV P2, A ;TURN ON PORT2 PIN 2
      ACALL DELAY
      MOV P2, #00h
      RET
		  
SUB4: MOV A, #08h                  
      MOV P2, A ;TURN ON PORT2 PIN 3
      ACALL DELAY
      MOV P2, #00h
      RET


 

i using a 8051 base chip
my program will receive serial data, then check for the four possibility to on the specify pin on port 2

the GETCMD code is take from the guide of Jon Ledbetter
the SUB1-SUB4 is wrote by me

if i receive the correct data on serial port, then i will turn on the port 2 pin so it can give 5v output at the pin
the port2 pin0-pin3 will connected to a npn transistor's base separately
i need to short the wire at collector of transistor to the wire at emitter when the base turn on

can i do so with my code?

any suggestion are welcome


Mathew