MITEL MH8841AS, MH8841AE, MH8841AN Datasheet

5-11



Features

• 1200 baud BELL 202 and CCITT V.23 Frequenc y Shift K eying (FSK) demo dulati on

• Compat ible wit h Bell core TR -NW T-000030 and SR-TSV-002476

• High inpu t sens itivi ty: -36dB m

• Simple serial 3-wire data interface eliminating the need for a UA RT

• Power do wn mo de

• Intern al gain ad ju stable a mp lifier

• Carrie r detec t statu s outp ut

• Uses 3.579545 MHz crystal or ceramic resonator

• Single 5V powe r supp ly

• Low pow er CMO S tech nolog y

Applications

• Calling Num ber De livery (CND), Ca lling Na me Delivery (CNAM) and Calling Identity on Call Waiting (CIDCW) feat ures of Bellcore CL AS S

service

• Featur e phone s

• Phone s et adj unc t boxes

• FAX machines

• Telephone An swer ing m achine s

• Database query systems

Description

The MT8841 Calling Number Identification Circuit (CNIC) is a CMOS integrated circuit providing an interface to various calling line information delivery services that utilize 1200 baud BELL 202 or CCITT V.23 FSK voiceband data transmission schemes. The CNIC receives and demodulates the signal and outputs d ata in to a simple 3-w ire se r ial in te rface.

Typically, the FSK modulated data containing information on the calling line is sent before alerting the called par ty or during the silent interval between the first and second ring using either CCITT V.23 recommendations or Bell 202 specifications.

The CNIC accepts and demodulates both CCITT V.23 and BELL 202 signals. Along with serial data and clock, the CNIC provides a data ready signal to indicate the reception of every 8-bit character sent from the Central Office. The received data can be processed externally by a microcontroller, stored in memory, or displayed as is, depending on the application.

Ordering Information

MT8841AE 16 Pin Plastic D IP MT8841AS 16 Pin SOIC MT8841A N 20 Pin SSO P

-40 °C to +85 °C

Figure 1 - Functional Block Diagram

CLASSSM is a service mark o f B ellcore

IN-

IN+

CAP V

Ref

DATA DR DCLK

PWDN OSC1 OSC2

SSVDD

IC1 IC2

Receive

Bandpass

Filter

Bias

Generator

FSK

Demodulator

Data and Timin g

Carrier

Detector

Clock

Generat or

Recovery

to other circuits

ISSUE 4 May 1995

MT8841

Calling Number Identification Circuit

CMOS

MT8841

5-12

Figure 2 - Pin Connections

Pin Description

Pin #

Name Description

16 20

11 IN+Non-inverting Op-Amp (Input). 22 IN-Inverting Op-Amp (Input). 33 GSGai n Sel ect (Outpu t). Gives access to op-amp out put for connection of feedback resistor. 44 V

Ref

Voltage Reference (Output). Nominally V

DD/2

. This is used to bias the op-amp inputs.

55 CAPCapacitor. Connect a 0.1µF capacitor to V

67OSC1Oscillator (Input). Crystal or ceramic resonator connection. This pin can be driven directly

from an external clocking source.

79OSC2Oscillator (Output). Crystal or ceramic resonator connection. When OSC1 is driven by an

external clock, this pin should b e left open.

810 V

Power supply ground.

9 11 DCLK Data Clock (Output). Outputs a clock burst of 8 low going pulses at 1202.8Hz (3.5795MHz

divided by 2976). Every clock burst is initiated by the DATA stop bit start bit sequence. When the input DATA is 1202.8 baud, the positive edge of each DCLK pulse coincides with the middle of the data bits output at the DATA pin. No DCLK pulses are generated during the start or stop bits. Typically, DCLK is used to clock the eight data bits from the 10 bit data word into a serial-to-parallel converter.

10 12 DATA Data (Outp ut). Serial data out put correspondi ng to the FSK inpu t and switching at the input

baud rate. Mark frequency at the input corresponds to a logic high, while space frequency corresponds to a logic low at the DATA output. With no FSK input, DATA is at logic high. This output stay s high un til CD

has become active.

11 13 DR

Data Ready (Open Drain Output ). This output goes low after the last DCLK pulse of each word. This can be used to identify the data (8-bit word) boundary on the serial output stream. Typically, DR

is used to latch the eight data bits from the serial-to -p arallel convert er into a

microcontroller.

12 14 CD

Carrier Detect (Open Drain Output). A logic low indicates that a carrier has been present for a specified time on the line. A time h ysteresis is provided to allow for mom ent ary di sconti nuit y of carrier.

13 15 PWDN Power Down (Input). Active high, Schmitt Trigger input. Powers down the device including the

input op-amp and the oscillator.

14 16 IC1 Internal Connection 1. Connect to V

. 15 19 IC2 Internal Connection 2. Internally connected, leave open circuit. 16 20 V

Positive power supply voltage.

6,8 17,

NC No Connection.

1 2

3 4 5

6 7 8

16 15 14 13 12

IN+

INGS

VRef

CAP OSC1 OSC2

VSS

VDD IC2 IC1 PWDN CD

DR DATA DCLK

16 PIN PLASTIC DIP/SOIC

1 2

3 4 5

6 7 8 9

20 19 18 17 16 15 14 13

IN+

IN-

VRef

CAP

OSC1

OSC2

VSS

20 PIN SSOP

VDD IC2 NC NC

PWDN CD DR DATA DCLK

IC1

MT8841

5-13

Functional Description

The MT8841 Calling Number Identification Circuit (CNIC) is a device compatible with the Bellcore proposal (TR-NWT-000030) on generic requirements for transmitting asynchronous voiceband data to Customer Premises Equipment (CPE) from a serving Stored Program Controlled Switching System (SPCS) or a Central Office (CO). This data transmission technique is applicable in a variety of services like Calling Number Delivery (CND), Calling Name Delivery (CNAM) or Calling Identity Delivery on Call Waiting (CIDCW) as specified in Custom Local Area Signalling Service (CLASS

) calling

information delivery features by Bellcore.

With CND, CNAM and CIDCW service, the called subscriber has the capability to display or to store the information on the calling party which is sen t by the CO and received by the CNIC.

In the CND service, information about a calling party is embedded in the silent interval between the first and second ring. During this period, the CNIC receives and demodulates the 1200 baud FSK signal (compatible with Bell-202 specification) and outputs data into a 3 - wir e se ria l i nte rfa c e.

In the CIDCW service, information about a second calling party is sent to the subscriber, while they are engaged in another call. During thi s period, the CNIC receives and demodulates the FSK signal as in the CND case.

The CNIC is designed to provide the data transmission interface required for the above service

Figure 3 - Differential Input Configuration

IN+

IN-

Ref

MT8841

DIFFERENTIAL INPUT AMPLIFIER

C1 = C2 = 10 nF R1 = R4 = R5 = 100 kΩ R2 = 60kΩ, R3 = 37.5 kΩ R3 = (R2R5) / (R2 + R5)

VOLTAGE GAIN

diff) = R5/R1

INPUT IMPEDANCE

diff) = 2

+ (1/ωC)

Figure 4 - Single-Ended Input Configuration

at the called subscriber location either in the on-hook case as in CND, or the off-hook case, as in CIDCW. The functional block diagram of the CNIC is shown in Figure 1. Note however, for CIDCW applications, a separate CAS (CPE Alerting Signal) detector is required.

In Europe, Caller ID and CIDCW services are being proposed. These schemes may be different from their North American counterparts. In most cases, 1200 baud CCITT V.23 FSK is used instead of Bell

202. Because the CNIC can also demodulate 1200 baud CCITT V.23 with the same performance, it is suitable for these applications.

Although the main application of the CNIC is to support CND and CIDCW service, it may also be used in any application where 1200 baud Bell 202 and/or CCITT V.23 FSK data reception is required.

Input Configuration

The input arrangement of the MT8841 provides an operational amplifier, as well as a bias source (V

Ref

)

which is u se d to b i as the inputs a t V

DD/2

. Provision is made for connection of a feedback resistor to the opamp output (GS) for adjustment of gain. In a singleended configuration, the input pins are connected as shown in Figure 4.

Figure 3 shows the necessary connections for a differential input configuration.

User Interface

The CNIC provides a powerful 3-pin interface which can reduce the external hardware and software requirements. The CNIC receives the FSK signal, demodulates it, and outputs the extracted data to the DATA pin. For each received stop bit start bit sequence, the CNIC outputs a fixed frequency clock string of 8 pulses at the DCLK pin. Each clock rising

IN+

IN-

Ref

MT8841

VOLTAGE GAIN

) = RF / R

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