ST7538Q datasheet(35/44 Pages) STMICROELECTRONICS

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ST7538Q

Functional description

35/44

5.11

Detection method and Rx Sensitivity in UART mode

When ST7538Q is running in UART mode (by forcing UART/SPI pin to “1”) the Control

UART mode provides also a third level of Receiving sensitivity in addition to two levels select

able by Control Register (see Table 11). By setting to “1” the TxD pin during a receiving

session the sensitivity is forced to BU threshold (this condition suppresses the Control

Table 12. Control register functions in UART mode

Function

Value

Selection

Note

Default

Bit 13

Bit 12

12 to

Detection

Method

Not Allowed

This configuration

should be avoided

because it could cause

an unpredictable

behavior of the device

Carrier

detection

without

conditioning

Not Allowed

This configuration

should be avoided

because it could cause

an unpredictable

behavior of the device

Carrier detection

without

conditioning

Carrier Detection

Notification on CD_PD

Line

CLR/T and RxD signal

always Present

Carrier detection

with conditioning

Carrier Detection

Notification on CD_PD

Line

CLR/T Line is forced to

“0” and RxD Line is

forced to “0” or “1”

(according the

UART/SPI pin level)

when Carrier is not

detected

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