COMPONENT MAINTENANCE MANUAL
AVIATION RECORDERS
FA2100CVR
Rev. 15 Page 45
Apr. 14/16
Description and Operation
23–70–04
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found, the indices are set to a pre
−
determined top of memory location. Once
the indices are restored, the CVR is ready to transition to the record state.
(2)
Record State
Figure 11 shows the word partition structure for the 2-Hr FA2100CVR, refer to
this figure for the following description. Once the FA2100CVR has been initial-
ized, recording will commence with the first digitized audio data received from
the Audio Compressor board. The CVR Executive task enables the TDM re-
ceive routine to begin collecting data form the Audio Compressor stream sent
over the TDM bus. The SMP software is responsible for all of the processing
needed to format the received audio data streams into a form ready for storage
into the CSMU. The complete sequential process is described in the steps be-
low:
(a)
The TDM interrupt handler receives the audio data stream from the Audio
Compressor hardware and buffers it into 8 ms blocks of data. Each of
these blocks contains four, 2 ms frames of interleaved digital samples of
the HQV, HQC, SQV, and SQC audio channels. Each 2 ms frame also
contains samples of GMT, rotor speed, and discrete inputs (push
−
to
−
test,
bulk erase).
(b)
The 8 ms blocks of audio data are split by the Audio Channelizer task.
This task “demultiplexes” the audio sample stream into the individual
streams that will be stored in the CSMU. The Audio Channelizer builds 36
word packets of data for each of the four stream types, HQV, HQC, SQV,
and SQC, along with 36 word packets of “special” data (GMT, rotor speed,
discretes). As each packet is filled, it is forwarded to the CVR Executive
task. Special packets containing GMT and rotor speed data are also built
and forwarded.
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