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CHAPTER 20 LIN-UART
20.6.1 Setting the Baud Rate
This section describes how the baud rates are set and the resulting serial clock
frequency is calculated.
■ Calculating the Baud Rate
The both 15-bit reload counters are programmed by the baud rate generator registers 1, 0 (BGR1/BGR0).
The following calculation formula should be used to set the desired baud rate:
Reload Value:
v = [Φ / b] - 1,
where Φ is the machine clock, b the baud rate and [] gaussian brackets (mathematical rounding function).
●
Example of calculation
If the machine clock is 16 MHz and the desired baud rate is 19200 bps baud then the reload value v is:
v = [16*10
6
/ 19200] - 1 = 832
The exact baud rate can then be recalculated: b
exact
= Φ / (v + 1), here it is: 16*10
6
/ 833 = 19207.6831
Note:
Setting the reload value to 0 stops the reload counter. For this reason the minimum division ratio is 2.
For asynchronous communication, the reload value must be greater than equal to 4 because 5 times
over-sampling is performed to determine the reception value internally.