Another thing to think about. If you have a newer variety 8051 derivative that can be clocked at a frequency faster than 12 MHz please evaluate the use of a crystal of such frequency as 18.432 MHz or 22.1184 MHz. Both of these can lead to accurate baud rate generation. The 18.432 MHz frequency will offer more exact standard baud rates when TIMER2 is used as the baud rate generator.

Michael Karas

PS. I have found 18.432 MHz crystals in surplus equipment numerous times.