Hello,
I was experimenting with driving a PCF8547P 8-bit IO chip today with a PIC12F683

I tested it out by having it drive an LED bargraph

I was scratching my head over the "optional" address parameter within the I2CWRITE command.
I searched around and noticed someone applied the value of zero to that parameter, for the PCF8547P chip.
But I didn't think it would work - because the I2C protocol within PCF8547P datasheet does not call for that parameter.
So I figured the PCF8547P wouldn't respond.

I was surprised to find however it did work!
So I'm curious to know what is going on with that optional "Address" parameter.
Does the I2CWrite function ignore it when it is zero?
If the I2CWrite function actually does send a zero - how is it that does not mess up the PCF8547P's protocol?

Thanks
dw