Dear Forum Members,

I am designing a product where I will be using two pcbs stacked one above another.
1. Master control card.
2. Motion control card.

The master control card has
a. 16 110V AC outputs.
b. 8 24V DC inputs.
c. LCD.
d. Keypad.
e. UART connecting to UART of motion control board.

The Motion control board has
a. 3 axis stepper motor driving.
b. 3 Shaft encoder inputs feedback from steppers.
c. 4 24V DC inputs from proximity switches.
d. UART connecting to UART of control board.

The UART link is TTL level and not RS232 since boards are stacked distance will be few cms. UART is for sending coordinates to motion card and when desired position is reached motion card sends its response.

Now the main question,
1. What is the best method to clock these two micros [P89V51RD2] on diffrent boards that are stacked? I use oscillators when two micros are on same board but never did two micros diffrent board.
2. I have read Eriks threads on clocks biting each other and that scares me? I have also experienced SMPS biting my cricuit in an earlier design.
3. Oscillator bus on physical wires is surely not a good idea is it?
4. Does stacking increase biting chances? Do I need some mettalic [ iron ] separation when stacking?

Thanks for reading my post. Waiting for your kind comments and suggestions.

Thanks & Regards,
Prahlad Purohit