DATA_ADDR  EQU 400H
COUNT      EQU 4
RAM_ADDR   EQU 30H
        ORG 0
        ACALL COPY_DATA
        ACALL CAL_CHKSUM
        ACALL TEST_CHKSUM
        SJMP  $
COPY_DATA:
        MOV  DPTR,#DATA_ADDR	
        MOV  R0,#RAM_ADDR	
        MOV  R2,#COUNT  	
H1:     CLR  A         	
        MOVC A,@A+DPTR   	
        MOV  @R0,A      	
        INC  DPTR     	
        INC  R0        	
        DJNZ R2,H1      	
        RET
CAL_CHKSUM:
        MOV  R1,#RAM_ADDR	
        MOV  R2,#COUNT  	
        CLR  A         	
H2:     ADD  A,@R1     	
        INC  R1      	
        DJNZ R2,H2     	
        CPL  A          	
        INC  A          	
        MOV  @R1,A     	
        RET
TEST_CHKSUM:
        MOV  R1,#RAM_ADDR	
        MOV  R2,#COUNT+1	
        CLR  A         	
H3:     ADD  A,@R1      	
        INC  R1        	
        DJNZ R2,H3     	
        JZ   G_1       	
        MOV  P1,#'B'   	
        SJMP OVER  
G_1:    MOV  P1,#'G'    	
OVER:   RET
        ORG 400H
MYBYTE: DB  25H,62H,3FH,52H
        END