I have been using a Phillips PCF8574 in a PIC16F876 circuit (via I2C)
quite successfully for several years. Picbasic works great with these
two.

However, when I substitute the Texas Instrument PCF8574 ic for the
Phillips one it no longer writes to the chip. I can read the TI chip
fine but cannot output to it.

What is going on? Aren't these two compatible with Picbasic?

Thanks for your help

Larryt