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ST72321xx-Auto Serial communications interface (SCI)
Doc ID 13829 Rev 1 153/243
15.7.7 Extended transmit prescaler division register (SCIETPR)
This register allows setting of the external prescaler rate division factor for the transmit
circuit.
Table 77. SCIERPR register description
Bit Name Function
7:0 ERPR[7:0]
8-bit Extended Receive Prescaler Register
The extended baud rate generator is activated when a value different from 00h is
stored in this register. Therefore the clock frequency issued from the 16 divider
(see Figure 64) is divided by the binary factor set in the SCIERPR register (in
the range 1 to 255).
The extended baud rate generator is not used after a reset.
SCIETPR Reset value: 0000 0000 (00h)
76543210
ETPR[7:0]
RW
Table 78. SCIETPR register description
Bit Name Function
7:0 ETPR[7:0]
8-bit Extended Transmit Prescaler Register
The extended baud rate generator is activated when a value different from 00h is
stored in this register. Therefore the clock frequency issued from the 16 divider
(see Figure 64) is divided by the binary factor set in the SCIETPR register (in the
range 1 to 255).
The extended baud rate generator is not used after a reset.
Table 79. Baud rate selection
Symbol Parameter
Conditions
Standard Baud rate Unit
f
CPU
Accuracy
versus
standard
Prescaler
f
Tx
f
Rx
Communication
frequency
8MHz
~0.16%
Conventional mode
TR (or RR) = 128, PR = 13
TR (or RR) = 32, PR = 13
TR (or RR) = 16, PR = 13
TR (or RR) = 8, PR = 13
TR (or RR) = 4, PR = 13
TR (or RR) = 16, PR = 3
TR (or RR) = 2, PR = 13
TR (or RR) = 1, PR = 13
300
1200
2400
4800
9600
10400
19200
38400
~300.48
~1201.92
~2403.84
~4807.69
~9615.38
~10416.67
~19230.77
~38461.54
Hz
~0.79%
Extended mode
ETPR (or ERPR) = 35,
TR (or RR) = 1, PR = 1
14400 ~14285.71
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