Rikard Bosnjakovic wrote:
> On 3/7/07, michael brown <n5qmg@earthlink.net> wrote:
>
>> Read about them, you need to know this stuff.  They're just like
>> option switches, you turn them on or off.  You'll see that the
>> CLKOUT stuff passes the Fosc/4 clock out a port pin making it
>> unusable to you.  The ER thingy is also tying up one of your port
>> pins thinking that you have an external R/C connected to act as the
>> clock.  You could try this for your CONFIG word settings:
>
> Thanks for your input. I've now read through about the configuration
> bits and port setups even more. Yet I seem to miss something, because
> PORTA won't change values when I try to.
>
>    __CONFIG _CP_OFF & _WDT_OFF & _BODEN_OFF & _PWRTE_ON &
> _INTOSC_OSC_NOCLKOUT & _MCLRE_OFF & _LVP_OFF
>
> start
>        clrf    PORTA
>        clrf    PORTB
>
>        ; reset and initialize ports
>        bsf     STATUS, RP0                     ; select bank1 for
> configuration of TRISA/TRISB
>        bcf     STATUS, RP1
>
>        movlw   b'00000111'
>        movwf   CMCON                           ; turn off the
> comparator function for PORTA

CMCON is in BANK0 on the 16F628


>        movlw   b'11111000'                     ; RA[3:7] inputs
>        movwf   TRISA                           ; RA[0:2] outputs
>
>        movlw   b'00000000'                     ; RB[0:5] outputs
>        movwf   TRISB                           ; RB[6:7] unusable
> (timer crystal)
>        bcf     STATUS, RP0

You need to move the CMCON stuff to right here

>        ; none of these below works, PORTA is still 0
>        movlw   1
>        movwf   PORTA
>        movlw   2
>        movwf   PORTA
>        movlw   3
>        movwf   PORTA
>        movlw   4
>        movwf   PORTA
>        movlw   5
>        movwf   PORTA
>        movlw   6
>        movwf   PORTA
>        movlw   7
>        movwf   PORTA
>        movlw   8
>        movwf   PORTA

The 8 shouldn't work and the 9 below should result in only a 1 since you 
only have three output bits.

>        movlw   9
>        movwf   PORTA
>
> Have I missed something obvious? Because I really can't understand
> what's going on.

Try the CMCON stuff, it'll work wonders.  ;-) 

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist