DS21354/DS21554 3.3V/5V E1 Single-Chip Transceivers
5.4. Automatic Alarm Generation
The device can be programmed to automatically transmit AIS or Remote Alarm. When automatic AIS
generation is enabled (CCR2.5 = 1), the device monitors the receive-side framer to determine if any of the
following conditions are present: loss-of-receive frame synchronization, AIS alarm (all ones) reception,
or loss of receive carrier (or signal). If any one (or more) of the above conditions is present, then the
framer will either force an AIS alarm.
When automatic RAI generation is enabled (CCR2.4 = 1), the framer monitors the receive side to
determine if any of the following conditions are present: loss of receive frame synchronization, AIS alarm
(all one’s) reception, or loss of receive carrier (or signal) or if CRC4 multiframe synchronization cannot
be found within 128ms of FAS synchronization (if CRC4 is enabled). If any one (or more) of the above
conditions is present, then the framer will either transmit a RAI alarm.
RAI generation conforms to ETS 300 011 specifications and a constant Remote Alarm will be transmitted
if the DS21354/DS21554 cannot find CRC4 multiframe synchronization within 400ms as per G.706.
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