ST72321R7-Auto datasheet(153/243 Pages) STMICROELECTRONICS

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ST72321xx-Auto

Serial communications interface (SCI)

Doc ID 13829 Rev 1

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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)

543

ETPR[7:0]

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

fCPU

Accuracy

versus

standard

Prescaler

fTx

fRx

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

~0.79%

Extended mode

ETPR (or ERPR) = 35,

TR (or RR) = 1, PR = 1

14400

~14285.71

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