Search at this forum it was discused many times bebore.

As a resume:

.You can use an external paralell uart like 8251 (It uses an intel bus and easier to interface than the motorola)

.Make a software uart. It should be the best for low data rates. Look al phillips website for examples

.Use a serial uart SPI or I2C to serial it uses less lines than the parallel unitas and have a lot of derivates with 1,2,4,8 serial and fifi buffer