M-8880

M-8880 DTMF Transceiver · · · · · · · · · · · · · Advanced CMOS technology for low power consumption and increased noise immunity Complete DTMF transmitter/receiver in a single chip Standard 6500/6800 series microprocessor port Central office quality and performance Adjustable guard time Automatic tone burst mode Call progress mode Single +5 Volt power supply 20-pin DIP and SOIC packages 2 MHz microprocessor port operation Inexpensive 3.58 MHz crystal No continuous f2 clock required, only strobe Applications include: paging systems, repeater systems/mobile radio, interconnect dialers, PBX systems, computer systems, fax machines, pay telephones, credit card verification Figure 1 Pin Diagram Functional Description M-8880 functions consist of a high-performance DTMF receiver with an internal gain setting amplifier and a DTMF generator that contains a tone burst counter for generating precise tone bursts and pauses. The call progress mode, when selected, allows the detection of call progress tones. A standard 6500/6800 series microprocessor interface allows access to an internal status register, two control registers, and two data registers. Input Configuration The input arrangement consists of a differential input operational amplifier and bias sources (VREF) for biasing the amplifier inputs at VDD/2. Provisions are made for the connection of a feedback resistor to the op-amp output (GS) for gain adjust- The M-8880 is a complete DTMF Transmitter/Receiver that features adjustab...