CML - Wireline Data and Telephony - CMX867A

The CMX867A is a multi-standard modem for use in telephone based information and telemetry systems.

Control of the device is via a simple high speed serial bus, compatible with most types of µC serial interface.
The data transmitted and received by the modem is also transferred over the same serial bus.
On-chip programmable Tx and Rx USARTs meeting the requirements of V.14 are provided for use with asynchronous data and allow unformatted synchronous data to be received or transmitted as 8-bit words.

A high quality DTMF decoder with excellent immunity to falsing on voice, and a standard DTMF encoder are included. Alternatively, these blocks can be used to transmit and detect user-specific, programmed single and dual-tone signals, call-progress signals or modem calling and and answering tones.

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.
The device also features a Hook Switch Relay Drive output and a Ring Detector circuit which continues to function when the device is in the Powersave mode, providing an interrupt which can be used to wake up the host µController when line voltage reversal or ringing is detected.

Block Diagram


  • V.22/Bell 212A 1200/1200 or 600/600 bps DPSK
  • V.23 1200/75, 1200/1200, 75, 1200 bps FSK
  • Bell 202 1200/150, 1200/1200, 150, 1200 bps FSK
  • V.21 or Bell 103 300/300 bps FSK
  • DTMF/Tones - Tx and Rx
  • Low-Power Operation with Standby Mode
  • Software and Hardware compatible with CML's CMX868/868A


  • Telephone Telemetry Systems
  • Remote Utility Meter Reading
  • Security Systems
  • Industrial Control Systems
  • Electronic Cash Terminals
  • Pay-Phones
  • Cable System TV Set-Top Boxes

Supply Requirement:

  • 2.7 to 5.5 V power supply