UM0934 datasheet(21/113 Pages) STMICROELECTRONICS

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UM0934

Physical layer

Doc ID 17389 Rev 2

21/113

3.6.6

Soft Start

When the ST7570 modem starts transmitting, the soft start feature allows to linearly

increase the power amplifier output gain from zero to the target value in a given time. This

option can be used to reduce the EM emissions. The duration of the soft start is

programmable by steps of 13

µs through the MIB object 00ACh (soft start, Section 6.5.33).

3.6.7

Programmable digital output

Pin PRESLOT/ZC/TS/BIT (refer to [1]) can be programmed to output the following

information:

●

PRESLOT: as soon as time-slot synchronization is achieved, it is low when the device

is able to accept a P_Data.Request (or M_Data.Request) and high otherwise

●

ZC: square wave toggling on every positive zero-crossing event. Its period is equal to

double the mains period

●

TS: square wave synchronous to the time-slot reference generated by the internal PLL.

Its period is equal to time-slot

●

BIT: square wave toggling at every bit time start, generated by the internal PLL. Its

period is 2*bit time.

●

TX_P: it is high when a transmission is in progress, low otherwise

●

RX_P: it is high when a reception is in progress, low otherwise

●

TXRX_P: it is high when the device is involved in a communication (transmission or

reception) through powerline

The desired information to be output can be selected through the MIB object 00A4h

(PRESLOT/ZC/TS/BIT and ZC_IN_D configuration, Section 6.5.31).

3.6.8

Zero-crossing signal fault detection

This feature, always active, is used to detect fault conditions on the external zero-crossing

signal causing loss of proper synchronization.

If no falling edges are detected on the input ZC signal within a given timeout (1.3 s as the

default value), no time-slot events are generated. After this fault condition, a reset is

required.

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