I am using the P89C668 in volume using the 8k ERAM (Xram inside chip).

The REAL advantage is that with this configuration ports 0 and 2 becomes free for I/O.

The full fledged PCA has led me to some designs that are beatutifully simple compared to the previous versions using timers.

I have not yet used the hardware IIC driver, but that will come.

The 668 sell for $5-$12 depending on volume (compare that to Cygnal).

Erik