16F88 RA6 and RA7 troubles

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  1. - 27th July 2007, 07:29 #1
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    Quote Originally Posted by gandora View Post
    I have been working with the 16F88 for sometime now, and despite that fact have yet to be able to configure and use the osc1 and osc2 pins as i/o porta.6 and porta.7.

    I know that this is an accessable feature of the 16f88 by configuring the FOSC2:FOSC0 bits to 7 (%110). So far I have not been able to figure it out even after over half a year, and I have searched everywhere online to no avail.

    Please if anyone has any information that could help me, and the many others I have found that don't have the answer either. I know the feature may be special to the 16f88 but we should still be able to access it.

    Many thanks to anyone who can give any input.
    %110 = 6
    %111 = 7
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  2. - 27th July 2007, 07:38 #2
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    A quick look would suggest you could add

    ANSEL = 0

    to the code in post #4 here and be up and running. (You would still need to set TRISA accordingly for those pins)

    http://www.picbasic.co.uk/forum/show...ighlight=16f88

    UPDATE: In fact, the ANSEL=0 would not be needed because RA6 and RA7 are never analog - should work as posted in #4
    Last edited by paul borgmeier; - 27th July 2007 at 07:42. Reason: UPDATE
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  3. - 27th July 2007, 08:42 #3
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    Melanie gets her whip out and locks Paul and Joe in a room for 'retraining'.

    RA6/OSC1 and RA7/OSC2 only comes alive when you use the 16F88 in it's Internal Oscillator mode... and that is a feature of the CONFIGURATION BITS of the PIC...

    So (assuming you're using the default MeLabs PM Assembler)...

    1. At the top of your program, along with your PIC device statements you need...

    @ DEVICE INTRC_OSC_NOCLKOUT

    or

    @ DEVICE pic16F88, INTRC_OSC_NOCLKOUT

    I refer you to...

    (a) the PICs Datasheet Section 15 Special Features of the CPU, Register Table 15-1 CONFIG1 Configuration Word.

    Also (b) http://www.picbasic.co.uk/forum/showthread.php?t=543

    Only then you will be able to use RA6 and RA7.

    2. However the game hasn't finished...

    This PIC has multiple Oscillator selection (see datasheet Section 4 Oscillator Configuration)... one of the very first lines of your program must set the OSCCON Register (see Datasheet Register Table 4-2 OSCCON) for the speed you want this PIC to run... (because the Power-On default is 31.25kHz) example...

    OSCCON=%01100000 ' Set PIC to 4MHz

    There's other things you can do too, but I won't go into that at this time...

    It's all in the Datasheet... crate of beer helps...

    Oooh... and make sure your PBP is up to date... something in the back of my mind is nagging me about early versions having a problem with the 16F88... go to the MeLabs website and check in the Versions list when the fix occurred...
  4. - 28th July 2007, 05:31 #4
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    Default Whips and Beer !

    Woooo Hoooo, Promises, promises, promises ! Now I can't remember what PIC means . . .
    If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
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  5. - 31st July 2007, 01:30 #5
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    Ohhh, lock me and whip me too please.

    On a more serious note, I recall reading somewhere
    (with certain programmers) there was a problem with
    erasing the F88 with internal osc configured. Keep this
    in mind if your have trouble reprogramming. Hopefully
    this won't apply to you.
  6. - 1st August 2007, 02:01 #6
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    Default Problems

    My programmer programs no problem, but it still just doesn't work.

    I know exactly what I need to do after reading the whole darned datasheet again (without any bear ;_, but using the setting in pbp is not working.

    I need to change the osccon to %1111100 (most important are that the last two are %00 this makes the pic use the fosc2:fosc0 registry determine the osc setup.

    the fosc2:fosc0 is bit 4 1-0 (i am not 100 percent clear on what that means if u have any insight) of the configuration word 1 register whose main address is 2007h.

    According to the legend for Configuration word 1 to achieve INTRC (INTERNAL OSC) with i/o on RA6 and RA7 the Fosc2:fosc0 registers need to be changed to %100.


    I have tried the _INTRC_OSC_NOCLKOUT, and it did not work, I had the same result.

    Now i'll try to break it down a little more.

    As a note actually putting the heading 0 on the osccon registry causes the pic to fail to work stabily. It is for now my belief that pbp puts the header there for you.

    osccon %111 (first three bits set osc frequincy)
    %1(makes us primary only on osc) %1(frequincy is stable ^^)

    And with the last two you have some options:

    %00 OSC is defined by FOSC<2>
    %01 T1OSC used as clock
    %10 INTRC FOR SYSTEM CLOCK
    %11 Reserved (I have no clue what that means, but I figure I shouldn't try it ^^)


    -------------------------------------------------------------------------

    So what I am trying looks something like this.
    Code:
    _pic16f88
_INTRC_OSC_NOCLKOUT 'hopefully this modifies the configuration word 1 but it doesn't seem to.

OSCCON=%1111100 'sets the osccon register

CMCOM=7  'turns comparators off.
ANSEL=%00000000 'porta all digital.

main:
HIGH porta.6
HIGH porta.7

GOTO main:

END

    Any help would be much appreciated and thankyou very much.
  7. - 1st August 2007, 02:41 #7
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    I sense more Whipping in the near future ...

    _pic16f88
    _INTRC_OSC_NOCLKOUT 'hopefully this modifies the configuration word 1 but it doesn't seem to.
    Or, you could opt for the Painless version ...

    Presetting Configuration Fuses (PIC Defines) into your Program
    http://www.picbasic.co.uk/forum/showthread.php?t=543
    <br>
    DT
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