Hi, I believe I have a work around but will describe the situation. I'm wanting to drive pins and readback the result. Odd pins are configured to write (push pull) and even to read. All pins had a 1.2k resistor in series and pairs of pins, e.g. 0.0 and 0.1, have their resistors joined (so there was 2.4k between 0.0 and 0.1). The junction of the pair of resistors is the test point. With the above arrangement the internal 4.7k pullup resistor on 0.0 raises the input voltage to about 1.8V which is sometimes interpreted as a 1. I've dropped my resistors to 330 ohm and that is satisfactory.With many micro controllers the pullup is switchable and I was hoping it was so with the 6501 but I guess not.Thanks,Ken.