*
Input monitoring

*
Fault recording.

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FMCS -CDU FUNCTIONAL DESCRIPTION

These are the sub-functions that the BITE and fault monitoring circuits do:
*
Input monitoring

*
Self checks during power-up and normal operation

*
Manual tests done by the ground crew.

The BITE and fault monitoring function sends fault data to the central maintenance computing function (CMCF) for display and fault recording.
For input monitoring, the CDU monitors inputs from all its line replaceable units (LRUs). The CDU monitors the integrity of input buses and does checks of the input signals to determine their status. Signal status includes inactivity and validity fail for ARINC 629 LRU data.
The ARINC 429 LRU transmitters use no computed data (NCD) and failure warning (FW) status conditions. The CDU does certain reasonableness checks for key data to guard against failures that it cannot detect.
For self checks the CDU does compatibility checks during power-up and internal monitoring during normal operation. Power-up checks are done at power-up and at BITE restarts.
Display and Control Function
The display control function receives these inputs:
EFFECTIVITY
BEJ ALL

*
CDU line select keys

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Keyboard entries

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Flight deck control panel inputs

*
AIMS FMF partition inputs

*
BITE/fault monitoring requests

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CMCF requests.

The display control function use the inputs to supply these outputs:
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Map data to the PDF

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Flight path mode data to the PDF

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Button push information

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Data load to the CMCF for operational program load

*
CDU page display data to the CDU

*
CDU messages that show in the CDU scratchpad

*
Fault and test data that goes to the CMCF.

The display control function of the CDU makes CDU page and message displays. The display control function also sends data to the PDF for map and flight path mode data. The CDU map and flight path mode data format is almost the same as the FMCF display function.
Liquid Crystal Display (LCD) Function
The LCD function has both color and gray scale capability.
The backlight driver assembly has:
*
Temperature sensors

*
Heaters

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FMCS -CDU FUNCTIONAL DESCRIPTION

*
Power supplies

*
Filament monitoring circuits.

The character generator has these functions:
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Interface control

*
Character generation control logic

*
Voltage references.

The LCD driver sends image data to the LCD for display.
The LCD shows color and gray scale text data. The LCD circuit also sends voltage reference data to the character generator and LCD driver for image compensation.
A manual control and a sensor on the front of the CDU permit brightness control.
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777 AIRCRAFT MAINTENANCE MANUAL

FMCS -CDU FUNCTIONAL DESCRIPTION

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FMCS -SYSTEM TESTS

General
These are the system tests for the flight management computing system:
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Control display unit (CDU), center

*
Control display unit, left

*
Control display unit, right.

CDU System Test
This test makes sure that the center, left, or right CDU operates correctly. The CDU display (screen) goes blank during the test. After you start the test, you can not stop it. This test takes less than one minute.
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777 AIRCRAFT MAINTENANCE MANUAL

FMCS -SYSTEM TESTS

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FMCS -CDU SPECIAL FUNCTIONS

General
The FMCS control display unit (CDU) special function makes sure the internal hardware and software operates correctly. During a special function, the CDU uses built-in test equipment (BITE) to do a power-up test. The special function also makes a CDU test patterns show on the CDU for operator inspection.
The MAT shows these CDU special function screens/dialogue boxes:
　
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