Matt,

> It might be better if you include all of the code you are running. You
> do not show any of the setup here. Have you set RC1/2 as digital pins?

Yes, in ANSEL.

> At power up, these pins will be configured for digital inputs.
> Either try clearing the relevant bits in ANSEL, or use RC4/5
> Also, make sure that you have cleared the relevant bits in TRISC to
> set the pins as outputs.

Yes.

I have mentioned tha the o/p toggles between +5V and 0V at low frequency bu=
t at higher frequencies, it does not reach 0V but reaches only 1V.

Regards

Ravi


> =

> Matt
> =

> On 9 July 2010 12:59, Ravi <chiptech@vsnl.com> wrote:
> >
> > Hello Everyone,
> >
> > EXPERIMENT 1
> >
> > I have a 16F676 @ 4MHz communicating with 24LC256 using RC1 =

> (SDA, with
> > 1K pull up) and RC2 (SCL).
> >
> > I am using bit bang technique.
> >
> > As observed on an oscilloscope, the SDA and SCL lines raise to =

> 5V and
> > fall to 1V but not to 0V.
> >
> > I removed the 24LC256 thinking it could be pulling the line high.
> >
> > Again, as observed on an oscilloscope, the SDA and SCL lines =

> raise to 5V
> > and fall to 1V (above TTL level) but not to 0V.
> >
> > I started single stepping the code. Now the SDA and SCL both =

> raise to 5V
> > and fall to 0V.
> >
> > I inserted some 10 uS delay between SDA and SCL lines changing the
> > state. Still no success.
> >
> > EXPERIMENT 2
> >
> > Removed the 24LC256.
> >
> > Ran the below code.
> >
> > =A0 =A0 =A0 =A0bsf portc,scl
> > =A0 =A0 =A0 =A0bsf portc,sda
> > =A0 =A0 =A0 =A0goto $+1
> > =A0 =A0 =A0 =A0bcf portc,scl
> > =A0 =A0 =A0 =A0bcf portc,sda
> > =A0 =A0 =A0 =A0goto $-5
> >
> > Same results.
> >
> > If I run this with 5 mS delay then the I/O lines reach 0v.
> >
> > I am unable to understand this behavior.
> >
> > Has anyone come across this type of behavior?
> >
> > Cheers
> >
> > Ravi
> > --
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