what do you want to do? Add a serial port to yout DSP? In this case, you
can use a UART like the 16C550 (National, includeing FIFO). This chip has
a 8bit databus and include 8 registers that you can access from your DSP.
The other side you need a digital to RS-232 pegelconverter like a MAX232.
The connection of the UART to the DSP depends heavily on the DSP you
are using. Mostly you have to insert wait states. Which device do you use?
16450 or 16C450 from National, ST, ... is a UART without FIFO buffer
16550 or 16C550 from National, ST, ... is a UART with FIFO
from Texas Instruments there are many other types, but I don't know
which you can buy in your contry...
Another possibility is to use a shift register or a CPLD (to build your own
UART).