Hi David (David Duffy), in <2.2.32.19970905031605.0067c7dc@dingo.cc.uq.edu.au> on Sep 5 you wrote:

> Has anyone tried to use the 12c509 at 9600 Baud ? (4Mhz OTP's)
> It works well at 2400 Baud, but even when using the on-chip calibration
> value not all chips work at 9600. I'm guessing that the timing must be
> off enough not to lock. The 509 is being fed from a PC via a RS-232 > TTL
> converter.

You should self-calibrate the chip!

Measure the start bit length on a known character (like modems that
autobaud on "A").  Do this often to ensure that temperatur changes cause no
errors.