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MB90420/5 (A) SERIES F
12.6.2 Baud Rate by Internal Timer (16-bit Reload Timer)
The setting when selecting the internal clock supplied from the 16-bit reload timer as the transfer clock of the
UART and the baud rate calculation are shown below.
n Baud rate by internal timer (16-bit reload timer)
When 110
is written to the CS2 to CS0 of the mode register (SMR0/1), the baud rate by the internal timer is
B
selected. Any baud rate can be set by the prescaler division ratio and the reload value of the 16-bit reload
timer. Figure 12.12 shows the baud rate selector by the internal timer.
Output of 16-bit reload timer
(The frequency is specified by
the prescaler division ratio
and the reload value).
Fig. 12.12 Baud Rate Selector by Internal Timer (16-bit Reload Timer)
Asynchronous baud rate =
Synchronous baud rate =
• Expressions to obtain baud rate
• Setting example of reload value (machine clock = 7.3728 MHz)
Baud Rate
38400
19200
9600
4800
2400
1200
600
300
Division ratio of prescaler of 16-bit reload timer
X :
—: Setting prohibited
2
MC-16LX FAMILY 16-BIT MICROCONTROLLERS HARDWARE MANUAL
(Selection of clock synchronous/asynchronous mode)
φ
X (n+1) × 2 × 16
φ
X (n+1) × 2
Table 12-14 Baud Rate and Reload Value
Clock Asynchronous (start–stop
synchronization)
1
X = 2
(machine cycle
(machine cycle
2-divided)
8-divided)
2
5
11
23
47
95
191
383
SMR0/1: CS2 to CS0 = 110
(Selection of internal timer)
Clock selector
1/1 (synchronous)
1/16 (asynchronous)
SMR0/1: MD1
φ: Machine clock frequency
bps
X: Division ratio of prescaler of
bps
n: Reload value of 16-bit reload
Reload Value
3
X = 2
X = 2
(machine cycle
2-divided)
—
47
—
95
2
191
5
383
11
767
23
1535
47
3071
95
6143
12-26
B
Baud rate
16-bit reload timer (2
timer (0 to 65535)
Clock Synchronous
1
3
X = 2
(machine cycle
8-divided)
11
23
47
95
191
383
767
1535
1
3
5
, 2
, or 2
)
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