UART wrong bound rate

[klangner]

It looks that at bound rate=9600 the timer sends data with the speed of ~888. And then computer can't understand the output.

[gergoerdi]

I think I just got bitten by this bug: https://arduino.stackexchange.com/q/47297/1568

However, I am confused by your comment. Do you mean that setting the rate to 9600 baud results in an effective rate of 888 baud? Doesn't that mean I should be able to get good output by setting the baud rate to 103783?

Because I've just now tried that, and I am now only getting garbage out, whereas when using the nominal baud rate of 9600, I am at least getting some bits (the lower nybble) right.

However, by using the only-slightly-off baud rate of 11000, I am now able to receive my 0x5a byte correctly at 9600 baud.