CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CMX866
V.22 bis Modem
with AT Commands
©
2008 CML Microsystems Plc
D/866/5 May 2008
Provisional Issue
Features Applications
•
V.22 bis, V.22 and Bell 212A QAM/DPSK
•
Telephone Telemetry Systems
•
V.23, Bell 202, V.21 and Bell 103 FSK
•
Remote Utility Meter Reading
•
Integral AT Command Set with 'Fast Connect'
•
Security
Systems
•
V.23 and Bell 202 'Fast Turnaround'
•
Industrial Control Systems
•
Support for Type 1 Caller Line Identification
•
Electronic Cash Terminals / ATMs
•
DTMF/Programmable Tones: Transmit and Receive
•
Pay-Phones
•
'Zero-Power' and Powersave Standby Modes
•
Cable TV Set-Top Boxes
•
Low Power Operation
•
EPOS
Terminals
1.1 Brief
Description
The CMX866 is a multi-standard modem for use in telephone based information and telemetry systems.
Control of the device is via AT commands over a simple 9600b/s serial interface, compatible with most
types of host µController. An RS232 compatible interface can be created by the addition of a Level
Converter. The data transmitted and received by the modem is also transferred over the same serial
interface. The on-chip µController interprets these AT commands and controls an internal DSP, which
provides the modem and anciliary functions such as Ring Detection, Call Progress Detection, Hook
Switch control and DTMF autodialling. User-specific DSP functions are also available via the AT
command set.
Hardware support is provided for V.23 and Bell 202 Fast Turnaround and for rapid return to AT Command
mode. A Fast Connect mode has been implemented to reduce modem connection time. Flexible line
driver and receive hybrid circuits are integrated on chip, requiring only passive external components to
build a 2 or 4-wire line interface. Complete examples of 2-wire line interfaces to an external host µC and
to an RS232 interface, including the additional components required for Type 1 CLI, are provided.
The device features a Hook Switch relay drive output and a Ring Detector circuit that remain operational
when the CMX866 is in 'Zero-Power' or Powersave mode, providing an interrupt which can be used to
wake up an external host µC, as well as the CMX866, when line voltage reversal or ringing is detected.
The device is also able to detect off-hook parallel phones by monitoring voice activity on the line.
The CMX866 takes 5mA (typ.) from a single 2.7–5.5V supply and comes in 28-pin SSOP/SOIC packages.