If you program the PIC, there is one programming language that builds a simple idea into a powerful system and still gives you a great deal of control over your program: Forth.
http://tutor.al-williams.com/picforth1.htm
uses a PIC16F84 micro and MAX3100 UART to impelement 256 address RS-485 bus transceiver
http://www.edn.com/article/CA179575.html
The 16F628 will run 16F84A code with only very minor modifications
http://www.finitesite.com/d3jsys/16F628.html
The reason to do this is that 16C55X one time programmable devices (OTP) are very cheap
http://www.phanderson.com/PIC/16C84/16C554.html
http://www.hth.com/filelibrary/TXTFILES/PIC16C84.TXT
4 steps to help you get started with PIC programming.
http://samengstrom.com/elec/pic/index.html
http://www.yty.net/pic/enindex.html
http://www.doc.ic.ac.uk/~ih/doc/pic/