MT88E45B

Data Sheet

4

Functional Overview

The MT88E45B is compatible with FSK and FSK

plus CAS (CPE Alerting Signal) based Caller ID

services around the world. Caller ID is the generic

name for a group of services offered by telephone

operating companies whereby information about the

calling party is delivered to the subscriber. In Europe

and some other countries Caller ID is known as

Calling Line Identity Presentation (CLIP). ETSI calls

CAS ‘Dual Tone Alerting Signal’ (DT-AS), BT calls it

‘Tone Alert Signal’.

Depending on the service, data delivery can occur

when the line is in the on-hook or off-hook state. In

most countries the data is modulated in either Bell

202 or CCITT V.23 FSK format and transmitted at

1200 baud from the serving end office to the

subscriber’s

terminal.

Additionally

in

off-hook

signalling, the special dual tone CAS is used to alert

the terminal before FSK data transmission. BT uses

CAS to alert the terminal prior to FSK in both on-

hook (Idle State) and off-hook (Loop State)

signalling.

In North America, Caller ID uses the voiceband data

transmission interface defined in the Bellcore

document GR-30-CORE. The terminal or CPE

(Customer Premises Equipment) requirements are

defined in Bellcore document SR-TSV-002476.

Typical services are CND (Calling Number Delivery),

CNAM (Calling Name Delivery), VMWI (Visual

Table 1 - CB0/1/2 Functionality

The number of control bits (CB) required to interface the MT88E45B with the microcontroller depends on the

functionality of the application, as shown in Table 2.

Table 2 - Control Bit Functionality Groups

CB0 CB1 CB2

FSK

Interface

Function

0/1

1

1

Set by CB0 FSK Demodulation. Tip/Ring input (GS1) selected. DR/STD is DR.

0/1

1

0

Set by CB0 Hybrid CAS Detection. Hybrid Receive input (GS2) selected. DR/STD is STD.

0/1

0

1

Set by CB0 Tip/Ring CAS Detection. Tip/Ring input (GS1) selected. DR/STD is STD.

When the line is off-hook, a Bellcore/TIA Multiple Extension Interworking (MEI)

compatible Type 2 CPE should be able to detect CAS from Tip/Ring while the

CPE is on-hook because it may be the ACK sender. Tip/Ring CAS detection is

also required for BT’s on-hook CLIP.

1

0

0

Mode 1

Power Down. The MT88E45B is disabled and draws virtually no power supply

current.

0

0

0

Mode 0

Reserved for factory testing.

Functionality Group

Control

s

Description

FSK (mode 0 or 1) and

Hybrid CAS only

(Non MEI compatible)

CB2

CB0 is hardwired to Vdd or Vss to select the FSK

interface.

CB1 hardwired to Vdd.

The microcontroller uses CB2 to select between the 2

functions.

FSK (mode 0 or 1),

Hybrid CAS,

Tip/Ring CAS

(MEI compatible or BT on-hook CLIP)

CB1

CB2

CB0 is hardwired to Vdd or Vss to select the FSK

interface.

The microcontroller uses CB1 and CB2 to select between

the 3 functions.

FSK (mode 1),

Hybrid CAS,

Tip/Ring CAS,

Power Down

(MEI compatible or BT on-hook CLIP)

CB1

CB2

CB0 is hardwired to Vdd to select FSK interface mode 1.

The microcontroller uses CB1 and CB2 to select between

the 4 functions.

FSK (mode 0), Hybrid CAS,

Tip/Ring CAS, Power Down

(MEI compatible or BT on-hook CLIP)

CB0

CB1

CB2

All 3 pins are required.