Square wave generation in Keil using timer with useful interrupt control

org 000h
MOV A,#00H
Mov IE,#88H
MOV TMOD,#10H
MOV TH1,#0FCH
MOV TL1,#66H
SETB TR1
WAIT:SJMP WAIT
ORG 001BH
CPL A
MOV P1,A
CLR TR1
CLR TF1
MOV TH1,#0FCH
MOV TL1,#66H
SETB TR1
RETI
END