PIC's ports individual bits manipulation - how to?

[flotulopex]

Hello,

In one of my projects, I have to adress the first (LSB) four bits of my PIC's PORTA.

This is done within a FOR...NEXT loop so the bits are adressed as a variable ("Digit").

I would like to use the other four bits for other purpose (Button, any Input...) but I can't make this the way I did it up to now.

How is it possible to handle ONLY those four bits wihtout modifying the other (MSB) four bits?

I've attached my code if you like to see how I've done it. Any comments/critics are very welcome.

[sayzer]

Hi flotulopex,

Check this http://www.picbasic.co.uk/forum/showthread.php?t=3753

May give you some ideas.


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[flotulopex]

Thank you sayzer,

I found this thread already. I tried Melanie's way but it doesn't work.

First, it looks as "Digit" won't increment from 0 to 3.

Second, I have put a "spy" before entering the loop. I put PORTA.6 = 1.

Since I use PIC Simulator, I can see the port status and as soon as the program has started, PORTA.6 goes back to 0 (!?).

Am I doing something wrong?

In my code's FOR...NEXT loop, I have put:

    for Digit = 0 to 3
        value_d = value dig digit
        lookup value_d, [$7E,$0C,$B6,$9E,$CC,$DA,$FA,$0E,$FE,$DE], Segments
        PORTA.0(Digit) = ~DCD Digit
        PORTB = Segments
    next

[skimask]

    for Digit = 0 to 3
        value_d = value dig digit
        lookup value_d, [$7E,$0C,$B6,$9E,$CC,$DA,$FA,$0E,$FE,$DE], Segments
        PORTA.0(Digit) = ~DCD Digit
        PORTB = Segments
    next

I'm not so sure that ~DCD Digit will work. I could be wrong. Maybe: ~ (DCD Digit) ?
And I don't see an initial 'ENABLE' in the program itself...not sure if that's needed either or if interrupts are 'ENABLE'd by default.
Ha...just found the answer to that last 'not sure'. Page 183 of the PBP manual states that interrupts are NOT enabled by default...so, you have to turn them on.

[SteveB]

How about something simple, like:

PORTA.0 = Digit.0
PORTA.1 = Digit.1
PORTA.2 = Digit.2
PORTA.3 = Digit.3

HTH,
SteveB

[flotulopex]

I just made this piece of code as test.

MYPORT  var PORTA
Loop    var BYTE
PORTA.0 = MYport.0
PORTA.1 = MYport.1
PORTA.2 = MYport.2
PORTA.3 = MYport.3

PORTA.6 = 1 'Test to check port's state change in simulator...

Start:
    for LOOP = 0 to 3
        myport.0[Loop] = 1  'High
        myport.0[loop] = 0  'Low
    next
    goto start
END

It works except the PORTA.6 will change it's status from 1 to 0 when the firt loop will be executed.

[mister_e]

PORTA.0(Digit) = ~DCD Digit

as you write to a BIT, it have to be 0 or 1 ONLY.

Use a LCD or a serial comm to see the results of ~DCD digit... it return 254, 253, 251, 247.

i bet PORTA.0[Digit]=1 is what you're looking for.