16F88 RA6 and RA7 troubles

[Melanie]

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...

[Archangel]

Woooo Hoooo, Promises, promises, promises ! Now I can't remember what PIC means . . .

[G-R-C]

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.

[gandora]

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.

_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.

[Darrel Taylor]

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
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