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ST7538

Transmission Mode

ulator and the Power Line Interface are turned ON. The transmit Data (TXD) enter synchronously or asyn-

chronously to the FSK modulator.

– Host Controller Synchronous Communication Mode: on CLR/T rising edge, TXD Line Value is read and

sent to the FSK Modulator. ST7538 Manage the Transmission timing according to the BaudRate Se-

lected

– Host Controller Asynchronous Communication Mode: TXD data enter directly to the FSK Modulator.The

Host Controller Manages the Transmission timing

In both conditions no Protocol Bits are added by ST7538.

The FSK frequencies are synthesized in the FSK modulator from a 16 MHz crystal oscillator by direct dig-

ital synthesis technique. The frequencies Table in different Configuration is reported in Table 3. The fre-

quencies precision is same as external crystal one’s.

In the analog domain, the signal is filtered in order to reduce the output signal spectrum and to reduce the

harmonic distortion. The transition between a symbol and the following is done at the end of the on-going

half FSK sinewave cycle.

Figure 12.

TRANSMISSION

FILTER

FSK

MODULATOR

D-TYPE

FLIP

FLOP

DAC

21

19

8

5

24

7

TIMER

THERMAL

SENSOR

VOLTAGE

LOOP

CURRENT

LOOP

CLR/T GENERATOR

ZERO CROSSING

23

29

Vsense

CL

ATOP2

ATOP1

ATO

CLR/T

TxD

TOUT

16

15

ZCIN

ZCOUT

Bit 14

Bit 0-5

Bit 0-2

Bit 7 & 8

Band Pass

PLI

ALC

PLI

PLI

D03IN1420