Description

The AS2540 is a CMOS integrated circuit that incorporates a speech circuit (line-adaptation, 2/4-wire conversion, separate Rx- and Tx-amplifiers for handset and modem), MF dialler, ring frequency detector, ring melody generator and a two wire serial interface. It shall act as an a/b-line-powered device in order to interface a main-powered CPU to the analogue telephone line.

AS2540 can operate in a so-called mainpower mode and in a backup mode. During mainpower mode, a watchdog timer is running on AS2540, which has to be reset via the serial interface, which is connected to the CPU through opto-couplers. During backup mode (= The main-power failure or SW engine problem), AS2540 can operate as an independent basic MF dialler
(digits 0-9*#).