UM0239 datasheet(18/44 Pages) STMICROELECTRONICS

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UM0239

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4.2.8

Frequency detection time

This parameter (Bits [10:9]) defines the time within which a carrier must be detected across

the Mains before signalling it on ST7540 CD/PD pin. If the Preamble Detection method is

selected, the CD/PD becomes active only if also a preamble is detected.

For more information, see Section 4.2.7: Detection method.

4.2.9

Output voltage freeze

The Output Voltage Freeze parameter (Bit 17) turns off the Voltage Control Loop once the

ALC remains in a steady condition for about 3 control loop periods and maintains a stable

condition until the end of transmission.

This function is available only if the Extended Control Register parameter (Bit 21) is

enabled.

4.2.10

Output clock

The Output Clock parameter (Bits [16:15]) sets the ST7540 MCLK line frequency as a sub-

multiple of the 16-MHz oscillator frequency or disables the output clock.

4.2.11

Header recognition

The Header Recognition parameter (Bit 18) enables the hardware recognition of one or

more headers (one 16-bit header or two 8-bit headers depending on the Header Length

parameter setting). Header recognition is signaled by the CD/PD line in different ways

depending on Frame Length Count (bit 19).

Note:

If synchronization software is used, this parameter must be disabled to ensure the correct

behavior of RX sessions.

This function is available only if the Extended Control Register parameter (Bit 21) is

enabled.

Table 11.

Frequency detection time

Bits [10:9]

Value (msec)

Bits [10:9]

Value (msec)

0.5

1 (default)

Table 12.

Output voltage freeze

Bit 17

Value

0Enabled

Disabled (default)

Table 13.

Output clock

Bits [16:15]

Value (MHz)

Bits [16:15]

Value (MHz)

4 (default)

Clock OFF

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