I have an old TI V.90 analog modem design based upon a TMS320C54V90 and a Si3016 DAA.
The design has worked well in the past and I have only recently encountered problems. I control the V.90 via AT commands across a serial port.
My problem situation is described in the steps below :
--Modem sees and incoming call and relays RING message to DTE
--DTE issues ATA command to answer incoming call
--Modem appears to go off-hook for less than one second, then returns to on-hook. This is verified with an external monitor, as the modem still thinks it is off-hook.
--If I monitor the audio, no answer tones are ever heard from the modem. I can call in from a hand-set and get nothing after the modem picks up.
--After about a 20 second timeout (about the time for a train-up session) the modem returns a 'NO CARRIER' message and the call terminates.
Questions are :
--What would make the modem not put out an answer tone ?
--Could the DAA be dropping the analog call because of some over-voltage or over-current condition?
--If the DAA does do above, can I get a status indicator of the event via some AT command?