Oleg,

I apologise, I thought you were saying I wasn't using MOVX when accessing the clock. I have now attached the external pull up resistors, as shown in the updated schematic.

As for setting bit IT1, it just slipped my mind, I had intended to make it edge triggered. As for enabling the interrupt before initialising the display, I don't know what was going through my head there, mustn't have been thinking straight. I have now rectified both of these problems.

Now to the OSC frequency. I'm using a 11.0592MHz oscillator. From my calculations this will give me Address Valid to ALE and Address Hold After ALE as approx 70ns which is loads of time for the DS12887 to latch the address. (I'm not using the x2 feature).

Even after making these changes I'm still getting the same response (or lack of) from the clock. Thanks for your help so far and any further help would be greatly appreciated.

Regards,
Ray