Here under are the I/O ports needed for my application :

- 14 for graphic LCD (8 datas, 6 control)
(For Michael : it hasn't serial capability. Driver is KS0108/KS0107)
- 3 for serial PLL (Enable, clock, data)
or 8 for parallel PLL
- 8 for matrix keyboard
- 6 digital outputs
- 2 digital input
- 2 or 9 for optical coder according to the model used.
- Let's say 8 spare I/O

Best case = 35 I/O
Worst case = 55 I/O

The graphic LCD timing is critical. It should be very difficult to communicate with it thru serial link (I2C?)

The coder should also be critical, but currently I'm not able to say which method I will use to connect it on uC.
All other I/O aren't too critical. The keyboard and general I/O may be implemented as I2C slaves or shifted registers for example.

Now I've to choose the more cost effective versus elegant solution to implement this. (see my first post).
For the moment the best I'm seeing is the I2C expanders for keyboard and general I/O and to keep the PLL, coder and LCD on the micro.

What's your feeling ?

Stephane