TDA7421 datasheet(17/38 Pages) STMICROELECTRONICS

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ttim = (IFRC + 1) / fosc

tcnt = (CF + 1697) / fIF

FM mode

tcnt = (CF + 44) / fIF

AM mode

Counter result succeeded:

ttim > tcnt - terr and

ttim > tcnt + terr

Counter result failed:

ttim< tcnt + terr or

ttim > tcnt - terr

where:

ttim = IF time cycle time

tcnt = IF counter cycle time

terr = discrimination window (controlled by the EW

registers)

The precision of the measurements is adjustable

by controlling the discrimination window. This is

adjustable by programming the control registers

EW0...EW2.

The measurement time per cycle is adjustable by

setting the register IFS0 - IFS2.

The center frequency of the discrimination win-

dow is adjustable by the control register "CF0" to

"CF4". The available values are reported in dat-

abyte specification

2C BUS INTERFACE

General Description

The TDA7421 supports the I

2C bus protocol. This

protocol defines the devices sending data into the

bus as transmitter and the receiving device as the

receiver.

The device that controls the transfer is a master

and the device being controlled is the slave. The

master will always initiates data transfer and pro-

vide the clock to transmit or receive operations.

Data Transition

Data transition on the SDA line must only occur

when the clock SCL is low. SDA transitions while

SCL is high will be interpreted as START or

STOP condition.

Start Condition

Phase Comparator

ttim

tcnt -tERR

succeeded

tcnt +tERR

failed

D96AU551

TDA7421

17/38

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