[SOLVED] PIC SFR not changing initial values

[mrinalmani]

I am using MPLAB X
The SFRs do not seem to be changing their initial values. After the following code, TRISB should = 0, and PORTB 7
but they do not change. (I am using the simulator)
Please help

start

    MOVLW   0H
    MOVWF   TRISB
    MOVLW   7H
    MOVWF   PORTB
    GOTO start
    END

 

[andre_luis]

Both TRISB and PORTB registers are located into different banks.
I presume you should insert these macros, as highlighted bellow:

start

MOVLW 0H
[B]bank1 [/B]
MOVWF TRISB
MOVLW 7H
[B]bank0[/B]
MOVWF PORTB
GOTO start
END

 

[wp100]

Hi,

As shown in the code example in the previous reply you need to use the Banksel Directive to tell the compiler which Memory bank the system and user registers are in.
It cannot decide for itself which memory bank the registers are in so its down to you to tell it from your code instructions, its painful and a bit of a chip design problem, but thats one of the drawbacks of using Assembler; C code deals with it for you.

You can also use Macros, as Andre shows, to make bank changing even simpler.

It would be helpful if you say what chip you are using/ simulating , but look at its Datasheet section /figure Memory 'Data Memory Map' which shows how the registers are organised.

 

[mrinalmani]

Yes, now it works after bank switching.
I was working with PIC16F877A
Thanks!