I'm currently working on a project that is using a Philips 87LPC764 and needs to talk to a couple of ICs via I2C. Currently I'm working with a Philips PCF8563 RTC.

I've based my initial code on that found in Philips' Application Note 422 ("Using The 8Xc751 Microcontroller As An I2C Bus Master").

The problem I am having is that while it appears I am initially getting control of the bus as an I2C master, I send only one bit of the address byte successfully--the second bit is sent but comes back with an "ARL" (Arbitration Lost) status instead of a "DRDY" (Data Ready) status. This happens in the "XmBit2" section of code (please see app note) at the first "JNB DRDY,XMErr".

My 87LPC764 is operating at 6 clocks/instruction mode with an 11.0592Mhz crystal.

I'm wondering if I could possibly be clocking data out to the RTC too quickly for its 400Kbps max rate? Or what else could cause the 87LPC764 to report an "arbitration lost" condition while trying to send the second bit of the address byte?

Any feedback would be appreciated.

Regards,
Craig Steiner