CMX644A
V.22 and Bell 212A
Modem
D/644A/6 June 2000
Provisional Issue
Features
•
•
•
•
•
•
V.22/Bell 212A Compatible Modem
Integrated DTMF Encoder
Call Progress/Accurate Answer Tone Detection
Line Reversal and Ringing Detector
Low Power Operation (2.7V)
Fully Integrated UART Functions
Applications
•
•
•
•
•
•
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 CMX644A V.22 modem is intended for use in any telephone based information and telemetry system with
low power requirements. Using V.22 signalling, fast call set up times and robust error resistant transmission
can be implemented by efficient low power circuits. The circuit can operate at 1200b/s full duplex over 2-or 4-
wire circuits. Control of the device is via a simple high speed serial bus and data may be optionally formatted
by the on-chip UART. 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. In addition to V.22, support is included
to meet the Bell 212A standard. The integrated DTMF encoder can be used as part of the dial out function.
All 16 DTMF combinations are available along with a single tone ‘melody’ mode.
The answer tone generator/detector and call progress tone detectors included on the CMX644A 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 CMX644A features a
‘Zero Power’ standby mode. Whilst in standby, the device can still detect a ringing voltage or line voltage
reversal. The CMX644A can operate on a supply voltage between 3.0V and 5.5V across the full temperature
range of -40°C to +85°C. A low impedance pull down output is provided for a hook relay. The CMX644A is
pin compatible with the CMX624 V23/Bell 202 modem also from CML.
©
2000
Consumer Microcircuits Limited
CMLMICRO [ CML MICROCIRCUITS ]
