ORG 00H
	JMP init

	ORG 23H
	RETI

	ORG 30H
init:
	MOV TMOD, #20H	; Timer 1 mode 2
	MOV TH1, #0FDH	; TH1 = FDH
	MOV SCON, #50H
	SETB TR1	; Start Timer 1
	
	; enable transmission and receiving
	CLR RI
	CLR TI

main:
	ACALL receive
	ACALL transmit
	ACALL blink
	JMP main

receive:
	JNB RI, $
	MOV A, SBUF
	CLR RI
	RET

transmit:
	MOV SBUF, A
	JNB TI, $
	CLR TI
	RET

hexprint:
	PUSH ACC
	MOV DPTR, #hex
	SWAP A
	ANL A, #0FH
	MOVC A, @A+DPTR
	ACALL transmit
	POP ACC
	ANL A, #0FH
	MOVC A, @A+DPTR
	ACALL transmit
	RET

blink:
	CLR P2.5
	CLR P2.5
	ACALL delay
	SETB P2.5
	SETB P2.5
	RET

delay:
	MOV R2,#07FH
	MOV R1,#0
d:	DJNZ R1, d
        DJNZ R2, d
	RET

hex:	DB "0123456789ABCDEF"

e:
	END