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AS2540 Datasheet(PDF) 5 Page - ams AG |
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AS2540 Datasheet(HTML) 5 Page - ams AG |
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5 / 19 page  Data Sheet AS2540 austriamicrosystems Revision 3.1 Page 4 of 18 Functional Description Modes of operation There are 4 possible modes: Idle Mode Manual hook-switch and electronic hook-switch (e.g. relay) is open (MHS ∩ EHS = logical 0), no ring signal is applied, the oscillator is stopped, signalling via the serial interface is not possible. Ringing Mode AS2540 is supplied via the ring capacitor and external path, manual hook -switch and electronic hook-switch is open (MHS ∩ EHS = logical 0), the oscillator is running, a valid incoming ringing is signalled via the serial interface to the CPU. If the CPU does not reply the AS2540 switches into backup mode and sends a ring melody to the MO output. Backup Mode Manual hook-switch and/or electronic hook-switch is closed (MHS ∪ EHS = logical 1), AS2540 is supplied with line current, the oscillator is running, the keyscan is enabled and the handset path is switched on, signalling via the serial interface is possible. After AS2540 has started dialling in backup mode, he must not be interrupted any more in order to ensure consistent dialling. A mode transition BM -> MPM is only possible before AS2540 has started dialling digits independently. Main Power Mode Manual hook-switch and/or electronic hook-switch is closed, AS2540 is supplied with line current (MHS ∪ EHS = logical 1), the oscillator is running, the keyscan is disabled, AS2540 is controlled via the serial interface, handset path or monitor path or modem path is on, signalling via the serial interface is possible. Select Operation Mode Command Message Switches ON Switches OFF <SetHandsetPath> SROH SROT & STIT <SetModemPath> SROT & STIT <SetMonitorPath> SROH & SROT STIT Example Main Power Mode LS ROH ROT M1 M2 TIT AGND Line LI RI STB CS CI DPn C1 C2 C3 R1 R2 MODE RFD -2dB +6dB +2dB Mask DTMF- generator DIALLER UART MO RxD TxD VDD EHS MHS VSS OSC Start-up in backup mode As soon as AS2540 is supplied with line current, the external Vdd capacitor will be charged up via the LI and VDD pin and after the Vdd voltage has reached the operating level, the handset path of the speech circuit is switched on. This off-hook status is also signalled to the internal logic via the MHS or EHS pin in order to start the pinscan and subsequently set the country specific modes. Additionally a <LineEvent> message is sent to the CPU. Start-up in ring mode When a ringing signal is applied to the line, Vdd of AS2540 is charged up via an external path. After Vdd has reached the operating voltage the oscillator starts and AS2540 discriminates the ring frequency. After a valid ring frequency is applied on the RFD pin, the logic sends a <LineEvent> message is sent to the CPU and a watchdog timer is started. When the <LineEvent> message is not quit by the CPU before the watchdog timer has finished the countdown, AS2540 changes into backup mode and sends out a melody via the MO pin. DC conditions The normal operating mode is from 15mA to 100mA. An operating mode with reduced performance is from 5mA to 15mA. In the line hold range from 0mA to 5mA the device is in a power down mode and the voltage at LI is reduced to a maximum of 3.5V |
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Similar Description - AS2540 |
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