Wireless Systems Design

Multi-Standard Modem Suits New-Generation Telemetry And Wireline Data Systems

CML Microcircuits is now offering a multi-standard modem for use in EPOS terminals and telephone-based information and telemetry systems that they claim provides all of the functions needed to construct an ITU V.32 bis automodem or a V.32, V.22 bis, V.22, V.21, and Bell 202/Bell 103-compatible modem operating under the control of external host timing.

The CMX869B provides operation from 14400 bits/s with automatic fallback through to 4800 bits/s, retrain, rate re-negotiation and automatic detection of V.22 and V.22 bis modems.

The CMX869B features a fully integrated HDLC framer/de-framer, CRC block, and HDLC/SDLC signaling—tasks that are essential to new generation EPOS systems, such as the expanding Chip-and-Pin terminals. Line input and line outputs can be single-ended or differential, and the line-output amplifier is capable of directly driving into a low-impedance transformer or opto-isolated DAA. The hybrid and gain control circuits are integrated on chip, requiring only passive external components to build a 2- or 4-wire line interface. A DTMF decoder, which provides immunity to falsing on voice, and a standard DTMF encoder are included. Alternatively, the device can transmit and detect user-programmed single and dual-tone signals, call progress signals, or modem calling and answering tones.

The CMX869B features a software-controlled output to drive a hook switch relay and a ring detector block that continues to function when the device is in Powersave mode. When a line voltage reversal or ringing signal is detected, the ring detector circuit provides an interrupt that can wake up the host µController.

The CMX869B is available in 24-pin plastic SOIC and TSSOP packages for $4.20 in quantity orders.

For more information, visitwww.cmlmicro.com.

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