Setting The Baud Rate - Fujitsu MB90390 Series Hardware Manual

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
Both 15-bit reload counters are programmed by the baud rate generator registers 0, 1 (BGR02/03 and
BGR12/13). The following formula shall 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 CPU clock is 16 MHz and the desired baud rate is 19200 bps baud then the reload value v is:
v = [16 × 10
The exact baud rate can then be recalculated: b
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 internally.
6
/ 19200] - 1 = 832
= φ / (v + 1), here it is: 16 × 10
exact
CHAPTER 20 UART2, UART3
6
/ 833 = 19207.6831
375