Want to Add 1 on portB by timer1 Interrupt, Code not working pic16f877A

[Noman93]

Org 0x00
include <p16f877a.inc>
goto main
org 0x04
movlw d'1'
addwf portb
bcf pir1,tmr1if
retfie

main:
Banksel trisb
movlw b'00000000'
movwf trisb
banksel t1con
movlw b'00111101'
movwf t1con
banksel intcon
movlw b'11111110'
movwf intcon
banksel pie1
movlw b'00000001'
goto main
end

 

[betwixt]

You are not telling it to put the result back in portb.

from the data sheet:

ADDWF Add W and f
Syntax: [ label ] ADDWF f,d
Operands: 0 ≤ f ≤ 127
d ∈ [0,1]
Operation: (W) + (f) → (destination)
Status Affected: C, DC, Z
Description: Add the contents of the W register
with register ‘f’. If ‘d’ is ‘0’, the
result is stored in the W register. If
‘d’ is ‘1’, the result is stored back
in register ‘f’.

However, it would be more sensible to use 'incf portb,f' instead.

Brian.