ORG	0000H
	CLR	P3.7

	MOV	SCON, #01010000B
	MOV	TMOD, #21h
	
	MOV	TH1, #high(232)
	SETB	TR1

WAIT:	JNB	RI, $
	MOV	A, SBUF
	SUBB	A, #'A'
	JNZ	WAIT
	SETB	P3.7  ;this is connected to a transistor and an LED

	END