Step 6 of 11

Enable interrupts (GIE and TMR0IE)

Goal

Turn on the enable chain: clear TMR0IF, set TMR0IE, GIE, and start the timer.

Without GIE = 1 no ISR runs — it is the global master switch.

Course sequence (Timer0): 1. BCF INTCON, TMR0IF — clear stale flag 2. BSF INTCON, TMR0IE — enable source 3. BSF INTCON, GIE — enable globally 4. BSF T0CON, TMR0ON — counter starts

Main loop (bucle) can stay empty: the ISR will drive the LED in step 8.

Follow these steps

In inicio, after both CALLs, add the four lines from the highlighted block.
Order: clear TMR0IF before enabling interrupts.
Build with no errors.
If you load in Proteus now, the LED will not blink yet — ISR body is missing.

Your file so far

						        LIST    P=18F4550
        #include <P18F4550.INC>

        CONFIG  FOSC = HS
        CONFIG  WDT = OFF
        CONFIG  LVP = OFF
        CONFIG  PBADEN = OFF

        ORG     0x0000
        GOTO    inicio

        ORG     0x0008
        GOTO    isr_alta

        ORG     0x0018
        GOTO    isr_baja

        CBLOCK  0x20
temp_w
temp_status
        ENDC

init_gpio:
        BCF     TRISB, 0
        BCF     LATB, 0
        RETURN

init_timer0:
        MOVLW   B'00000111'
        MOVWF   T0CON
        MOVLW   B'01100111'
        MOVWF   TMR0H
        MOVLW   B'01101010'
        MOVWF   TMR0L
        RETURN

isr_alta:
        RETFIE

isr_baja:
        RETFIE

inicio:
        CALL    init_gpio
        CALL    init_timer0
        BCF     INTCON, TMR0IF   ; limpia bandera antes de habilitar
        BSF     INTCON, TMR0IE   ; habilita interrupcion Timer0
        BSF     INTCON, GIE      ; maestro global
        BSF     T0CON, TMR0ON    ; arranca el timer
bucle:
        GOTO    bucle

        END

What you add in this step

						        BCF     INTCON, TMR0IF
        BSF     INTCON, TMR0IE
        BSF     INTCON, GIE
        BSF     T0CON, TMR0ON

Checklist before you continue

I added the four enable lines in inicio.
I know GIE is required for any ISR.
Builds with no errors.

I completed this step