Datasheet
14 - SERIAL CHANNELS ST10F269
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Asynchronous Mode Baud rates
For asynchronous operation, the Baud rate
generator provides a clock with 16 times the rate
of the established Baud rate. Every received bit is
sampled at the 7th, 8th and 9th cycle of this clock.
The Baud rate for asynchronous operation of
serial channel ASC0 and the required reload
value for a given Baud rate can be determined by
the following formulas:
(S0BRL) represents the content of the reload
register, taken as unsigned 13-bit integer,
(S0BRS) represents the value of bit S0BRS (‘0’ or
‘1’), taken as integer.
Using the above equation, the maximum Baud
rate can be calculated for any given clock speed.
Baud rate versus reload register value (SOBRS=0
and SOBRS=1) is described in Table 28. and
Table 29
Note: The deviation errors given in the Table 28 are rounded. To avoid deviation errors use a Baud rate
crystal (providing a multiple of the ASC0/SSC sampling frequency).
B
Async
=
f
CPU
16 x [2 + (S0BRS)] x [(S0BRL) + 1]
S0BRL = (
f
CPU
16 x [2 + (S0BRS)] x B
Async
) - 1
Table 28 : Commonly Used Baud Rates by Reload Value and Deviation Errors (PQFP144 devices)
S0BRS = ‘0’, f
CPU
= 40MHz S0BRS = ‘1’, f
CPU
= 40MHz
Baud Rate (Baud) Deviation Error
Reload Value
(hexa)
Baud Rate (Baud) Deviation Error
Reload Value
(hexa)
1 250 000 0.0% / 0.0% 0000 / 0000 833 333 0.0% / 0.0% 0000 / 0000
112 000 +1.5% / -7.0% 000A / 000B 112 000 +6.3% / -7.0% 0006 / 0007
56 000 +1.5% / -3.0% 0015 / 0016 56 000 +6.3% / -0.8% 000D / 000E
38 400 +1.7% / -1.4% 001F / 0020 38 400 +3.3% / -1.4% 0014 / 0015
19 200 +0.2% / -1.4% 0040 / 0041 19 200 +0.9% / -1.4% 002A / 002B
9 600 +0.2% / -0.6% 0081 / 0082 9 600 +0.9% / -0.2% 0055 / 0056
4 800 +0.2% / -0.2% 0103 / 0104 4 800 +0.4% / -0.2% 00AC / 00AD
2 400 +0.2% / -0.0% 0207 / 0208 2 400 +0.1% / -0.2% 015A / 015B
1 200 0.1% / 0.0% 0410 / 0411 1 200 +0.1% / -0.1% 02B5 / 02B6
600 0.0% / 0.0% 0822 / 0823 600 +0.1% / -0.0% 056B / 056C
300 0.0% / 0.0% 1045 / 1046 300 0.0% / 0.0% 0AD8 / 0AD9
153 0.0% / 0.0% 1FE8 / 1FE9 102 0.0% / 0.0% 1FE8 / 1FE9