EM78811 View Datasheet(PDF) - ELAN Microelectronics

Part Name

Description

Manufacturer

EM78811

8-BIT MICRO-CONTROLLER FOR TELECOM PRODUCT

ELAN Microelectronics 

EM78811

8-BIT MICRO-CONTROLLER FOR TELECOM PRODUCT

FSK FUNCTION

Tip

Ring

Ring det1

/Ring Time

Band Pass

Filter

FSK

demodul

Data Valid

Energy Det

Circuit

Ring

Det

Circuit

Power /FSKPWR

Up

DATA OUT

/CD

/RD

OSC in

OSC out

CLOCK

Fig15. FSK Block Diagram

Function Descriptions

The CALLER ID IC is a CMOS device designed to support the Caller Number Deliver feature which is offered

by the Regional Bell Operating Companies.The FSK block comprises two paths: the signal path and the ring

indicator path. The signal path consist of an input differential buffer,a band pass filter, an FSK demodulator and

a data valid with carrier detect circuit. The ring detector path includes a clock generator, a ring detect circuit and

a power-up logic circuit.

In a typical application, the ring detector maintains the line continously while all other functios of the chip are

inhibited. If a ring signal is sent, the /RINGTIME pin will has a low signal. User can use this signal to wake up

whole chip or read /RD signal from RA register.

A /FSKPWR input is provided to active the block regardless of the presence of a power ring signal. If /FSKPWR

is sent low, the FSK block will power down whenever it detects a valid ring signal, it will power on when

/FSKPWR is high.

The input buffer accepts a differential AC coupled input signal through the TIP and RING input and feeds this

signal to a band pass filter. Once the signal is filtered, the FSK demodulator decodes the information and sends

it to a post filter. The output data is then made available at DATA OUT pin. This data, as sent by the central office,

includes the header information (alternate “1” and “0”) and 150 ms of marking which precedes the date , time

and calling number. If no data is present, the DATA OUT pin is held in a high state. This is accomplished by an

carrier detect circuit which determines if the in-band energy is high enough. If the incoming signal is valid and

thus the demodulated data is transferred to DATA OUT pin . If it is not, then the FSK demodulator is blocked.

* This specification are subject to be changed without notice.

10.12.1998 21

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