UM0239 datasheet(16/44 Pages) STMICROELECTRONICS

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UM0239

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4.2.2

Baudrate

The Baudrate parameter (Bits [4:3]) defines the speed of communication.

4.2.3

Deviation

The Deviation parameter (Bit 5) defines the frequency difference between the mark and the

space frequency. When set to “0.5”, the difference is one-half the Baud Rate value.

Otherwise, the difference is the Baud Rate value itself.

4.2.4

Interfacing mode

The (Mains) Interfacing mode (Bit 14) defines, when transmitting or receiving data across

the Mains, if the timings are managed by ST7540 by means of CLR/T line (Synchronous

mode) or by the host (Asynchronous mode).

In Asynchronous mode, data enter directly in the FSK modulator in Transmission mode and

are sent directly from the demodulator to the RxD line in Reception mode.

In the current software/firmware release, only Synchronous interfacing mode is available.

Due to the fact that Asynchronous Mains interfacing mode is the ST7540 default value, the

user must write at least once to the CR (in Synchronous interface mode) before the GUI will

perform any other action (except CR reading).

Table 4.

Carrier frequency

Bits 2 to 0 (MSB to LSB)

Value (kHz)

Bits 2 to 0 (MSB to LSB)

Value (kHz)

000

100

82.05

001

101

010

110

011

111

132.5 (default)

Table 5.

Baudrate

Bits 4 to 3 (MSB to LSB)

Value (bps)

Bits 4 to 3 (MSB to LSB)

Value (bps)

2400 (default)

600

4800

Table 6.

Deviation

Bit 5

Value

“0.5“ (default)

1“1“

Table 7.

Mains interfacing mode

Bit 14

Value

Synchronous

Asynchronous

(default)

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