serial port baudrate tolerance

[7rots51]

I want to use internal RC osc of xmega micro that have 1.5% tolerance in -40-85 temperature range,if I want to use its serial port with baudrate of 1200 to 115200 bps.
Is this tolerance acceptable for serial ports? what tolerance in baudrate is acceptable for ports without error in data reception?

 

[IanP]

Most users of RS-232 serial communication agree that any baud rate error over 3% is likely to cause communication errors, so 1.5% should be all right ..

IanP

 

[sg962]

According to standard, as i know, it must be in 1%

 

[7rots51]

In practical receivers ,how much tolrerance is acceptable without error in reception?3% or 1%?

 

[IanP]

In practice +/-3% tolerance is more realistic ..

The serial port receiver can tolerate a 3.0% overspeed and a 2.5% underspeed baud rate deviance

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or

Now we can calculate our allowable error as a percentage. For the normal scenario, the clock mismatch error can be ±5/152 = ±3.3%, and for the nasty scenario it can be ±3/152 = ±2%. As hinted earlier, although the problem will materialize at the receive end of the link, clock mismatch is actually a tolerance issue shared between the transmit and receive UARTs.

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IanP