I have a keypad with 89c51rd2 connected to a backend control unit (having P87LPC764) through RS485 link working at 9600 bauds. The unit works fine for days together. But suddenly the RD2 jumps to 12 clock mode and hence the baud rate changes and communication fails because of this. The processor goes back to 6 clock mode if power is cycled once. Has anyone faced such a problem? Any suggestions? The system needs to operate continuously all the 24 hours.