Hello good afternoon friends, I tell you that I am new to learning microcontrollers, now I am trying to use timer 1, using the overflow interrupt in PIC 12F629, the program what I would have to do is for about half a second to turn on a LED and another half second to turn it off and so on, I don't know if I am making a mistake in the configuration or I need to add something to the interrupt service subroutine, of course thanks for your help, the program is following: prueba04.asm [986] I copy it and paste it below: ; test_04 = It is about using, configuring and implementing timer 1 ; of PIC 12F629 causing an LED to light around medium ; second and turn off about half a second successively. LIST P = 12F629 INCLUDE <P12F629.INC> __CONFIG _CP_OFF & _CPD_OFF & _WDT_OFF & _BOREN_OFF & _MCLRE_ON & _PWRTE_ON & _INTRC_OSC_NOCLKOUT #DEFINE LED GPIO, GP0 ORG 0 goto Home ORG 4 goto Interrupcion_TMR1 Start bsf STATUS, RP0 clrf TRISIO call 03FFh movwf OSCCAL movlw b'00000001 ' movwf FOOT1 bcf STATUS, RP0 movlw b'00000000 ' movwf TMR1L movwf TMR1H movlw b'00110101 ' movwf T1CON movlw b'11000000 ' movwf INTCON Principal Main goto TM_1 interruption movlw b'00000000 ' movwf TMR1L movwf TMR1H btfsc LED goto is on bsf LED goto FinInterrupcion Its on bcf LED End Interrupt bcf PIR1, TMR1IF retfie ORG 03FFh retlw b'10000000 ' END