The 16C452 and 552 are a single chip implementations of the old "AT" style Dual Serial Adapter. It is a dual 80c450 or '550 type of UART with a "PS-2" Parallel port.

PC Programming books will give you all the programming info you need.

If there is any software "kink" it's that you use the LCR register to "alias" the Bit Rate Divisor Hi and Lo registers into place (over the normal RBR/THR & IIR registers) write them and then (using LCR) restore the normal reg's into place.

The electrical interface is straight-forward.
You connect 8 bit data, 3 least sig Addrs. lines RD&WR strobes as you would any std periph.

You also provide a CLK which in combination with 16 bit divisor registers set the bit rate for UART (or ACE) 0 and 1.

If there is any hardware "kink" it's that you must seperately decode ACE 0, ACE 1, and PPort. Since there are 8 Reg addrs locations per ACE your decode must provide at least this amount of space between UART base addrs. The PPort has only two register addresses.

Also, there are 3 (low going) interrupts 1 per UART/PPort. They can "Wire-OR" so you can allocate 1 8051 interrupt if your willing to poll each UART and PPORt to see who is Asserting the service request.

regards,
p