Step 5 of 11

Configure Timer0 (no ISR yet)

Goal

Set up Timer0 in 16-bit mode with prescaler 1:256 and initial value for ~2 s @ 20 MHz.

Timer0 is the most common interrupt source when starting. Flags TMR0IE and TMR0IF are in INTCON — not PIE1/PIR1.

Important: Timer0 does not need PEIE. Chain is: set T0CON + TMR0H/L → then (step 5) enable TMR0IE and GIE.

Values 0x676A come from Timer 0 — 2 s example.

Follow these steps

Replace empty init_timer0 RETURN with highlighted lines (T0CON, TMR0H, TMR0L).
Do not set TMR0ON or GIE yet — only configure the timer.
Build with no errors.
Optional: compare T0CON with the table in Timer 0.

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'    ; 16 bit, interno, prescaler 1:256
        MOVWF   T0CON
        MOVLW   B'01100111'    ; TMR0H = 0x67
        MOVWF   TMR0H
        MOVLW   B'01101010'    ; TMR0L = 0x6A  (~2 s @ 20 MHz)
        MOVWF   TMR0L
        RETURN

isr_alta:
        RETFIE

isr_baja:
        RETFIE

inicio:
        CALL    init_gpio
        CALL    init_timer0
bucle:
        GOTO    bucle

        END

What you add in this step

						init_timer0:
        MOVLW   B'00000111'    ; 16 bit, interno, prescaler 1:256
        MOVWF   T0CON
        MOVLW   B'01100111'    ; TMR0H = 0x67
        MOVWF   TMR0H
        MOVLW   B'01101010'    ; TMR0L = 0x6A
        MOVWF   TMR0L
        RETURN

Checklist before you continue

`init_timer0` loads T0CON and TMR0H/L initial values.
I understand Timer0 does not use PEIE.
Builds with no errors.

Tip: PEIE is for Timer1/2/3, UART, ADC… — not Timer0.

I completed this step