MM74HC943 300 Baud Modem
General Description
The MM74HC943 is a full duplex low speed modem. It provides
a 300 baud bidirectional serial interface for data communication
over telephone lines and other narrow bandwidth
channels. It is Bell 103 compatible.
The MM74HC943 utilizes advanced silicon-gate CMOS
technology. Switched capacitor techniques are used to peform
analog signal processing.
MODULATOR SECTION
The modulator contains a frequency synthesizer and a sine
wave synthesizer. It produces a phase coherent frequency
shift keyed (FSK) output.
LINE DRIVER AND HYBRID SECTION
The line driver and hybrid are designed to facilitate connection
to a 600X phone line. They can perform two to four wire
conversion and drive the line at a maximum of b9 dBm.
DEMODULATOR SECTION
The demodulator incorporates anti-aliasing filters, a receive
filter, limiter, discriminator, and carrier detect circuit. The
nine-pole receive filter provides 60 dB of transmitted tone
rejection. The discriminator is fully balanced for stable
operation.