CMX624 Datasheet PDF - Consumer Microcircuits Limited

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CMX624
Consumer Microcircuits Limited

Part Number CMX624
Description Bell 202 And V.23 Modem
Page 26 Pages


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D/624/6 January 2001
Features
V.23 / Bell 202 Compatible Modem
Integrated DTMF Encoder
Call Progress Tone Detection
Line Reversal and Ring Detector
Low Power Operation (2.7V)
Part of the CMX6x4 Modem Series
CMX624
V.23/Bell 202 Modem
Applications
Provisional Information
Telephone Telemetry Systems
Remote Utility Meter Reading
Security Systems/Cash Terminals
Industrial Control Systems
Pay-Phones
Cable TV Set-Top Boxes
1.1 Brief Description
The CMX624 V.23 / Bell 202 modem is intended for use in any telephone based information and telemetry
system with low power requirements. Using FSK signalling, fast call set-up times and robust error resistant
transmission can be implemented by efficient low power circuits. The circuit can operate at 1200bps full
duplex over a 4-wire circuit or 1200 bps plus low speed data over a 2-wire circuit. Flexible line driver and
receive hybrid circuitry are integrated on chip requiring only passive external components to build a 2- or 4-
wire interface. A low impedance pull down output is provided for a hook relay.
Control of the device is via a simple high speed serial bus; this allows easy interfacing to a host µController.
The data transmitted and received by the modem is also transferred over the same high speed serial bus. On-
chip programmable Tx and Rx UARTs allow asynchronous data to be simultaneously encoded and decoded.
Either UART may be disabled to allow 8-bit raw data to be received or transmitted. Any repetitive 8-bit data
pattern can be sent without the controller having to reload data every 8 bits. All 16 DTMF combinations are
available along with a single tone 'melody' mode. The ringing, 2100Hz, call progress and data detectors
included on the CMX624 make the set-up of a telephone call a simple matter for the host µController.
In many data collection and telemetry systems low power consumption is important. The CMX624 features a
'Zero Power' standby mode. Whilst in standby the ring detector continues to operate and will supply the host
µController with an interrupt when line reversal or ringing is detected. The CMX624 can operate on a supply
voltage between 3.0V and 5.5V across the full temperature range of -40°C to +85°C.
The CMX624 is pin compatible with the CMX644A V22 and Bell 212A modem also from CML.
© 2001 Consumer Microcircuits Limited
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V23 / Bell 202 Modem
CMX624
Section
CONTENTS
Page
1.1 Brief Description .......................................................................................1
1.2 Block Diagram ...........................................................................................3
1.3 Signal List...................................................................................................4
1.4 External Components ...............................................................................6
1.5 General Description ..................................................................................6
1.5.1 Xtal Osc and Clock Dividers.......................................................6
1.5.2 Rx Input Amplifier ........................................................................7
1.5.3 Receive Filter and Equaliser.......................................................7
1.5.4 FSK Demodulator.........................................................................8
1.5.5 Rx Energy Detector .....................................................................8
1.5.6 FSK / DTMF Modulator ................................................................8
1.5.7 Transmit Filter ..............................................................................9
1.5.8 Transmit Output Buffer .............................................................10
1.5.9 Ring Signal Detector..................................................................10
1.5.10 Tx/Rx UART.................................................................................11
1.5.11 ‘C-BUS’ Interface........................................................................13
1.5.12 ‘C-BUS’ Registers ......................................................................14
1.6 Application Notes....................................................................................14
1.6.1 Line Interface..............................................................................15
1.6.2 Ring Detector Interface .............................................................17
1.7 Performance Specification.....................................................................19
1.7.1 Electrical Performance..............................................................19
1.7.2 Packaging....................................................................................24
Note: This product is in development: Changes and additions will be made to this specification. Items
marked TBD or left blank will be included in later issues.
© 2001 Consumer Microcircuits Limited
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V23 / Bell 202 Modem
1.2 Block Diagram
CMX624
Figure 1 Block Diagram
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V23 / Bell 202 Modem
1.3 Signal List
CMX624
D2/D5/P4
Signal
Description
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Name
Type
XTALN
O/P The output of the on-chip Xtal oscillator inverter.
XTAL/CLOCK I/P The input to the oscillator inverter from the Xtal
circuit or external clock source.
SERIAL
CLOCK
I/P The ‘C-BUS’ serial clock input from the µC. See
Section 1.5.11
COMMAND
DATA
I/P The ‘C-BUS’ serial data input from the µC.
REPLY DATA T/S A 3-state ‘C-BUS’ serial data output to the µC.
This output is high impedance when not sending
data to the µC.
CSN
I/P The ‘C-BUS’ transfer control input provided by
the µC.
IRQN
O/P A ‘wire-ORable’ output for connection to a µC
Interrupt Request input. This output is pulled
down to Vss when active and is high impedance
when inactive. An external pullup resistor is
required.
TOP
TXO
TXN
TXON
VSS
VBIAS
O/P
O/P
I/P
O/P
Power
O/P
The Tx analogue signal output.
The output of the line driving amplifier.
The inverting input to the line driver amplifier.
The inverted output of the line driving amplifier.
The negative supply rail (ground).
Internally generated bias voltage of VDD/2,
except when the device is in ‘Zero Power’ mode
when VBIAS will discharge to VSS. Should be
decoupled to VSS by a capacitor mounted close
to the device pins.
RLYDRV
O/P Relay drive open drain output. This output is
pulled down to VSS when active and is high
impedance when inactive.
RXP
I/P The non-inverting input to the Rx input amplifier.
CMX624
© 2001 Consumer Microcircuits Limited
www.DataSheet.in
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