>
> I want to use portA to read two switches for one project and four
> switches for another.  How do I make each bit rotate through the carry
> flag consecutivly.  I have been using the following code, but it only
> reads the first bit. I am using a 16c56
>
>
>              movlw         0x0F
>              tris              PORTA
>              movlw         0x00
>              tris              PORTB
>
> input      bcf              STATUS, C
>              rrf               PORTA, W

This is a problem right here. Since you are sending the result to W, only
bit 0 of port A will be transferred to the carry bit.

>              btfsc            STATUS, C
>              goto             code_1
>              rrf               PORTA, W
>              btfsc            STATUS, C
>              goto             code_2
>              goto             input
>
> I was able to write the rest of this program and simulate it with
> success and I have been stareing at this part for four hours with no
> luck.

Two ways to solve it:

1. Copy portA to a temp register, then rotate that.

2. Skip the rotate completely and simply poll each bit with a bit test. The
reason that a lot of uControllers used rotate for this type of operation
ius simply because they couldn't test a bit directly. PIC's can so why not
use it.

3. You can mask out the bits in port A you're interested in and loop until
a switch is actually pressed. Then do a bit test to figure out which switch
was pressed.

Just a couple of thoughts. I think PIC's code set has other ways of solving
the problem.

BAJ