Low-speed Modems

General Description

The 73K324BL is a highly integrated single-chip modem IC which provides the functions needed to construct a V.22bis compatible modem, capable of 2400 bps full-duplex operation over dial-up lines. The 73K324BL is an enhancement of the 73K324L single-chip modem which adds the hybrid hook switch control, and driver to the 73K324L. The 73K324BL integrates analog, digital, and switched-capacitor array functions on a single chip, offering excellent performance and a high level of functional integration in a 32-Lead PLCC package.
The 73K324BL operates from a single +5 V supply for low power consumption.
The 73K324BL is designed to appear to the systems designer as a microprocessor peripheral, and will easily interface with popular single-chip micro-processors (80C51 typical) for control of modem functions through its 8-bit multiplexed address/data bus or via an optional serial control bus. An ALE control simplifies address demultiplexing. Data communications normally occur through a separate serial port.
The 73K324BL is pin and software compatible with the 73K222BL and 73K224BL, allowing system upgrades and product differentiation with a single component change.
The 73K324BL is designed to be a complete V.22bis compatible modem on a chip. The complete modem requires only the addition of the phone line interface, a control microprocessor, and RS-232 level converter for a typical system. Many functions were included to simplify implementation of typical modem designs. In addition to the basic 2400 bps QAM, 600/1200 bps DPSK and 300/1200 bps FSK modulator/demodulator sections, the device also includes synch/asynch converters, scrambler/descrambler, call progress tone detect, DTMF tone generator capabilities and handshake pattern detectors. Test features such as analog loop, digital loop, and remote digital loopback are supported. Internal pattern generators are also included for self-testing.


  • Includes features of 73K324L single-chip modem
  • On chip 2-wire/4-wire hybrid driver and off hook relay buffer
  • One-chip multi-mode V.22bis/V.22/V.21/V.23 and Bell 212A compatible modem data pump
  • FSK (300/1200 bps), DPSK (600, 1200 bps), or QAM (2400 bps) encoding
  • Software compatible with other Semi-conductor K-Series one-chip modems
  • Interfaces directly with standard micro-processors (80C51 typical)
  • Parallel or serial bus for control
  • Selectable asynch/synch with internal buffer/debuffer and scrambler/descrambler functions
  • All asynchronous and synchronous operating modes (internal, external, slave)
  • Adaptive equalization for optimum performance over all lines
  • Programmable transmit attenuation (16 dB, 1 dB steps), selectable receive boost (+18 dB)
  • Call progress, carrier, answer tone, unscrambled mark, S1, and signal quality monitors
    DTMF, answer, SCT, and guard tone generators
  • Test modes available: ALB, DL, RDL, mark, space, alternating bit, S1 pattern
  • CMOS technology for low power consumption (typically 100 mW @ 5 V) with power-down mode (15 mW @ 5 V)
  • TTL and CMOS compatible inputs and outputs


Previous article73K224L
Next article73M2901
The Smart Energy International editorial team is a multi-nation group of journalists and sector specialists based around the world. Click on the mail icon below to get in touch.