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CHAPTER 23 UART/SIO DEDICATED BAUD RATE GENERATOR
23.3 Operations
23.3
Operations
The UART/SIO dedicated baud rate generator serves as the baud rate generator
in clock asynchronous mode (UART).
■ Baud Rate Setting
The CKS bit in the SMC1n register of the UART/SIO is used to select the serial clock. This
selects the UART/SIO dedicated baud rate generator.
In asynchronous clock mode, the shift clock that is selected by the CKS bit and divided by four
is used and transfers can be performed within the range from −3% to +3%. The baud rate
calculation formula for the UART/SIO dedicated baud rate generator is shown below.
Figure 23.3-1 Baud Rate Calculation Formula when UART/SIO Dedicated Baud Rate Generator
Baud rate =
UART dedicated baud rate generator
prescaler select register (PSSRn)
Prescaler select (PSS[1:0])
Table 23.3-1 Sample Asynchronous Transfer Rates by Baud Rate Generator
(Machine Clock = 10MHz, 16MHz, 16.25MHz)
UART/SIO Dedicated baud rate
generator setting
Prescaler select
Baud rate counter
PSS[1:0]
setting BRS [7:0]
1 (Setting value: 0, 0)
1 (Setting value: 0, 0)
1 (Setting value: 0, 0)
1 (Setting value: 0, 0)
1 (Setting value: 0, 0)
2 (Setting value: 0, 1)
4 (Setting value: 1, 0)
8 (Setting value: 1, 1)
The baud rate can be set in UART mode within the following range.
Table 23.3-2 Baud Rate Setting Range in Clock Asynchronous Mode (UART)
488
Is Used
Machine clock (MCLK)
1
4
2
×
4
8
UART
Total division ratio
internal
(PSS × BRS × 4)
division
20
4
22
4
44
4
87
4
130
4
130
4
130
4
130
4
PSS[1:0]
0b00 to 0b11
FUJITSU SEMICONDUCTOR LIMITED
2
×
:
255
UART dedicated baud rate generator
baud rate setting register (BRSRn)
Baud rate setting (BRS[7:0])
Baud rate
(10 MHz /
Total division
ratio)
80
125000
88
113636
176
56818
348
28736
520
19231
1040
9615
2080
4808
4160
2404
BRS[7:0]
0x02 (2) to 0xFF (255)
MB95630H Series
[bps]
Baud rate
Baud rate
(16 MHz /
(16.25 MHz /
Total division
Total division
ratio)
ratio)
200000
203125
181818
184659
90909
92330
45977
46695
30769
31250
15385
15625
7692
7813
3846
3906
MN702-00009-1v0-E
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