The CFDIU ensures the following functions so as to establish the ECAM REPORT:
 -Selection of the valid FWC bus.
 -Reading filtering and memorization of label 357.
 -Association of GMT and of the flight phase with each ECAM warning message memorized.
The CFDIU establishes the AVIONICS STATUS.
 At each sequential scrutinization of all buses of Type 1
 and 2 systems and of discretes of Type 3 systems, the
 CFDIU:

 -Monitors the non-refreshment of label 356. After confirmation over 4 seconds, the CFDIU associates a NO X DATA message with this event, X being the identify of the system. If the system resumes normal transmission, the message is deleted.
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 d
_

 So the CFDIU operates in real time, to the nearest system scrutinization period.
 -Monitors systems status:
 *
 Type 1 and 2 systems The CFDIU monitors the status of bits 20 and 21 of the initial STX word of label 356 on the systems input buses. If bit 21 is set to 1, this means that the system is currently affected by a system internal or external fault (class 1, 2 or 3). If bit 20 is set to 1, this means that the system is currently affected by a class 3 fault. The CFDIU associates the identity of the system, with respect to its input port, with bit 21 and the indication CLASS 3 with bit 20. Example : ILS1. If bit 21 returns to 0, the CFDIU deletes the system identity display.

 *
 Type 3 systems The status of Type 3 systems is given by the status of the discrete connected to the CFDIU. The discretes are monitored regularly and the system status can be managed in real time. The CFDIU associates system identity with each incorrect status detection (Capacity: 40 lines of 24 characters).

The CFDIU carries out EVENTS CORRELATION
 -Principle of the fault correlation function. The purpose of the fault correlation function is to memorize in the CFDIU only one fault message for a given "aircraft fault event". The general principle of this function is therefore to group round a single message all messages which may occur further to a given aircraft event. This single message is as near as possible to the primary fault which generated this aircraft event.
 -Criteria of fault correlation and application "window". . Criterion of correlation The criterion of correlation of the fault messages (association or exclusion) is defined by means of the ATA reference of the LRU incriminated by the message. This reference is given by the first 2 labels 356 which follow the STX of the fault message. As a general rule the messages are associated if their ATA reference is nearly the same, i.e.:
 * in most cases, if the first 3 digits of the ATA
 reference are identical

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 22-81 22-82 22-83 22-8N 23-11 23-12 23-13 23-1N 26-10 26-12 26-13 26-1N 27-92 27-93 27-94 27-95 27-9N 31-32 31-33 31-36 31-3N 32-41 32-49 32-4N 34-35 34-36 34-37 34-3N 34-41 34-42 34-48 34-4N 34-51 34-52 34-53 34-55 34-5N 73-25 73-2N XX-XX XX-XX
N different from 1, 2 or 3
N different from 1, 2 or 3
N different from 0, 2 or 3
N different from 2, 3, 4 or 5
N different from 2, 3 or 6
N different from 1 or 9
N different from 5, 6 or 7
N different from 1, 2 or 8
N different from 1, 2, 3 or 5
N different from 5
+
 23-13

+
 22-83

 23-2X-XX + 46-2X-XX letters
 . Application window
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 *
 Under DC1 3 complete cycles of scanning of the input ports, the cycles being counted from the input port on which correlation processing was initiated or 1 minute from the fault which initiated correlation processing if duration of the 3 scanning cycles is less than 1 minute (to enable systems to transmit their faults).

 *
 Under DC2 The period between detection of the internal fault which initiated a correlation processing and DC2/DC1 transition plus 1 minute (as systems transmit the external faults at DC2/DC1 transition only).

 -General rules of correlation processing The starting point of fault correlation is an aircraft event. Depending on fault confirmation time of each system and according to scanning principle of the CFDIU this aircraft event is detected in the CFDIU through reception of internal fault(s) or external fault(s), although it is not possible to know whether the internal failure will precede or follow the external fault.
　
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