ST7540 datasheet(18/44 Pages) STMICROELECTRONICS

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Functional description

ST7540

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6.4

ST7540 Mains access

ST7540 can access the Mains in two different ways:

●

Synchronous access

●

Asynchronous access

The choice between the two types of access can be performed by means of Control

Reception Mode (for how to set the communication Mode, see Section 6.5).

In data transmission mode:

●

Synchronous Mains access: on clock signal provided by ST7540 (CLR/T line) rising

edge, data transmission line (TxD line) value is read and sent to the FSK Modulator.

ST7540 manages the Transmission timing according to the BaudRate Selected.

●

Asynchronous Mains access: data transmission line (TxD line) value enters directly to

the FSK Modulator. The Host Controller manages the Transmission timing (CLR/T line

should be neglected).

In data reception mode:

●

Synchronous Mains access: on clock signal recovered by a PLL from ST7540 (CLR/T

line) rising edge, value on FSK Demodulator is read and put to the data reception line

(RxD line). ST7540 recovers the bit timing timing according to the BaudRate Selected.

●

Asynchronous Mains access: Value on FSK Demodulator is sent directly to the data

reception line (RxD line). The Host Controller recovers the communication timing

(CLR/T line should be neglected).

600

132.5

600

75684

76335

132161

132813

1200

0.5

75684

76335

1200

0.5

132161

132813

75358

76660

131836

133138

2400

0.5

75358

76660

2400

0.5

131836

133138

74870

77148

131348

133626

4800

0.5

74870

77148

4800

0.5

131348

133626

73568

78451

130046

134928

Table 8. ST7540 synthesized frequencies

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