Oops. For some reason I didn't copy the first part of the response. It answers your question about the internal oscillator accuracy effecting timer accuracy. The system clock drives the UART baud rate generator and timers (see page 225 of the datasheet), so the UART question answers your timer question also.

Question:
How is the RS232 CLK affected by the drift in the internal OSC?

Answer:
The RS232 baud clock is derived from a timer that is usually sourced by SYSCLK or a divided version of it. This means that the variances in SYSCLK translate directly to variances in the baud rate.

Because of the inherent variability in the internal oscillator, it's useful in applications that have an 'auto-baud' mode that actively measures the incoming bit width and sets the UART timer based on those measurements. This typically works only slower baud rates.

Date: 09/22/2000

(also from Cygnal, not me)

- Lee