COMPONENT MAINTENANCE MANUAL
AVIATION PRODUCTS
Model FA5000
Rev. 02 Page 10
July 21/17
Description and Operation
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the restrictions on the cover page of this document.
B.
DataLink Task
The DataLink task is used to process ARINC 429 data received from avionics equipment
external to the recorder. Normally, the source of data is some type of Air Traffic Service
Unit (ATSU). The DataLink task analyzes the data coming in from the ARINC 429 input
port and decides which DataLink protocol is currently being used. This task will be able to
support both the Williamsburg Version 1 and Version 3 DataLink protocols although only
the Version 3 protocol will initially be enabled. Note that this task will only support the
“broadcast” mode of the Version 3 DataLink protocol although ALOHA messages will be
processed and ALOHA RESPONSE messages will be sent.
The DataLink task looks to see if there is any data in the DataLink Input FIFO that is auto-
matically filled by the hardware. If there is data in the FIFO, this routine reads the data
and analyzes it. The first thing that is checked is the ARINC 429 label. The recorder will
only accept data that has a label of 156, 157, 227, 270, or 276. Data with any other label
is discarded, except for Label 350, as discussed below. If the Williamsburg Version 1 pro-
tocol is enabled in the recorder and it is determined that the Williamsburg Version 1 proto-
col is in effect (i.e. the recorder is not using Williamsburg Version 3 protocol), then the
“CVR Ident” signal determines which labels the recorder will accept. If the “CVR Ident”
signal is high (indicating recorder #1), then the recorder will accept labels 157, 227, 270,
and 276. If the “CVR Ident” signal is low (indicating recorder #2), then the recorder will
accept labels 156, 227, 270, and 276. If the Williamsburg Version 3 protocol is in effect,
then the “CVR Ident” signal is not used and all labels (156, 157, 227, 270, and 276) are
accepted. Note that messages with Label 156 should not be sent when using the
Williamsburg Version 3 protocol; however, the recorder will record them if they are sent.
Label 350 is the CVR Status word that is output by the recorder from the OMS task. This
word is also sent from the OMS task to the DataLink task so that it can be recorded along
with the DataLink messages. Since this word is output at a one second rate, the GSE can
use this as a time marker. Recording this message may also be useful for flight data anal-
ysis since it indicates the state of the recorder as the DataLink messages are recorded.
When processing the Williamsburg Version 3 protocol, the data is collected into packets
and forwarded to the Data Storage task so that it will be stored in the CSMU. The layout
of how these packets are stored in flash memory is shown in Figure 10. This is all that is
required since there is never any response to received messages when running the Ver-
sion 3 protocol. Packets will also be forwarded to the GSE task for real-time monitoring
purposes. If this task has the Version 1 protocol enabled, then all of the received words
are looked at to determine whether a protocol response is needed or not. All words re-
ceived before the “Version 1/Version 3” determination is made will be stored as “Version
3” data. Once a “Version 1” determination is made, then appropriate responses are made
according to the dictates of the protocol.
Note that the entire 32-bit word received at the ARINC 429 DataLink message input port
will be stored. The recorder has more than enough memory to store the entire data word
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