Single-Chip 300-Baud Modem with DTMF Transceiver

The MC145446A is a silicon gate CMOS frequency shift keying (FSK) modem intended for use with telemeter systems or remote control systems over the telephone network. It replaces the MC145446.
This device also includes a serial control interface and internal control and status registers that permit a CPU to exercise the following built–in features:

• Single 5 V Power Supply
• Compatible with CCITT V.21
• DTMF Generator and Receiver for All 16 Standard Digits
• Capable of Driving 0 dBm into a 600 Ω Load (VCC = 5 V)
• AGC (Auto Gain Control) Amplifier for DTMF Receiver
• Imprecise Call Progress Tone (400 Hz) Detector
• A Transmit Attenuator Programmable in 1 dB Steps
• 2100 Hz Answer Tone Generator
• Serial Control Interface
• Analog Loopback Configuration for Self Test
• Power–Down Mode, Less than 1 µA