Shankaar G:

I believe from your first thread on this subject you said you were using the Philips P89C669 chip?

You may not be aware but Philips data sheet for the part.... http://www.semiconductors.philips.com/acrobat/d...669-02.pdf .... does not do a very good job of showing how the PCA functions work. They just show the SFR addresses and bits in a table.

There is also an available users manual of over 100 pages that has much more information about the PCA on this chip. Here is a link to the '669 users manual.

http://www.semiconductors.philips.com/acrobat/u...C669_3.pdf

Michael Karas