Em 9/7/2010 10:25, Ravi escreveu:
> Isaac,
>
>> It doesn't seem to be really a RMW problem. RMW will make a pin have the
>> *wrong* state ( 1 or 0 ), but not an *undefined* state.
>>
>> The OP said that the pin stays at 1V for a long period (over 10us if I
>> understood correctly). This is not '1' nor '0'.
>>
>> Things to check:
>>
>> 1) Is the pull-up really connected? Isn't it of a too low value?
> 1K pull up on SDA (RC1) line and no pull up on SCL (RC2) line. This is =

> being used for SEEPROM.
>
>> 2) Is the code really outputting a '0'? (check bank selection, perhaps
>> TRISx is not being written).
> I am checking on an oscilloscope. That's why i am able to see the =

> voltage at 1V.
>
> If I increase the delay to about 1mS, then the voltage reaches 0.
>
> I had used this code as is in other PICmicro.
>
> Cheers
>
> Ravi

If you set the oscilloscope time base to some appropriated value, can
you see the voltage on the pin falling from 1V to around 0V? Does this
fall resemble a capacitor discharge curve?

Does the voltage fall from 5V to 1V quickly (ns range), then the fall
rate reduces around 1000 times?

Do you have any additional components connected to the I2C signals? Can
you rule out damage to the PIC or memory? Can you replace them to be
sure none of them is damaged?
The ground connection between both chips is good and low resistance? The
scope probe ground is also connected to the PIC's ground in a good manner?


Best regards,

Isaac

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