Ravi,

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?
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.

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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