Am79C432A ISM PhoX Controller For Digital Cordless Telephones Datasheet

Am79C432A ISM PhoX Controller for Digital Cordless Telephones

The Am79C432A PhoX Controller is a highly integrated, low-voltage implementation of the baseband functions needed by digital cordless telephones on a single chip, including audio processing, protocol control, data formatting, and peripheral functions.

The PhoX chip implements a 32 kbit/s voice channel and a 1-, 2-, or 16 kbit/s control channel between the handset and the base station. Under the control of the on-chip 8051-class microcontroller, the Formatter performs all of the protocol requirements as well as baseband transmission and reception.

Baseband transmit data is available unfiltered as a Non-Return to Zero (NRZ) pseudo-digital signal, which is passed to the external RF transceiver for filtering and transmission. Data can also be filtered on-chip to provide analog Gaussian minimum-shift key (GMSK) output for external RF transceivers that require this format.

The voice channel is a 32 kbit/s ADPCM (Adaptive Differential Pulse Code Modulation) stream. The PhoX controller converts analog voice input at the microphone interface into ADPCM format and converts ADPCM received data into analog output at the earpiece or loudspeaker output. The device also provides digitally generated DTMF and ringing tones.

The Am79C432A incorporates many peripheral functions necessary for digital cordless telephones. For example, it has a 36-key keypad scanner, a serial port for interfacing to EEPROMs or serial LCDs, and a host of multifunction ports.

The brain of the PhoX chip is the 80C32T2, an 8051-class 8-bit microcontroller, which, with appropriate software, controls the audio path and services the various on-chip peripherals. The on-chip 1.25 Kbyte static RAM is used for variable storage. For software development, the chip interfaces directly to standard 8051 in-circuit emulators in Emulation mode.

The Am79C432A is designed for power management in a battery-operated environment. It has a low power dissipation while operating over a 2.7 to 3.6 V supply. The chip also includes a very low power Shutdown mode. For battery support, there is a battery-level measurement facility.

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