*
BITE and fault monitoring

*
Maintenance page access.

CDU -Inputs Overview
The CDUs receive air data inertial reference unit (ADIRU) data on the flight controls ARINC 629 buses.
The CDUs receive digital data on the systems ARINC 629 buses from these components:
* Audio management unit (AMU)
EFFECTIVITY
BEJ ALL

*
CDU (2)

*
ARINC signal gateway (ASG) (2)

*
Bus power control unit (BPCU)

*
Overhead panel ARINC system (OPAS) (2)

*
Autopilot flight director computer (AFDC) (3)

*
AIMS intercabinet ARINC 629 bus 2

*
AIMS FMCF data.

The CDUs receive digital data on the ARINC 429 bus from the satellite communication data unit (SDU).
The center CDU also gets data from the passenger address/ cabin interphone (PA/CI) controller.
The CDUs receive analog discretes from the master dim and test module.
The CDUs receive digital flight plan data on the AIMS intercabinet bus (ICB) 2 from the active FMCF.
ADIRU Inputs -Flight Controls ARINC 629 Bus (L and R)
The ADIRU sends inertial data to the CDUs. The CDUs use this data to calculate LNAV commands when the active FMCF fails. The CDUs receive this data from the ADIRU:
*
ADIRU mode (alignment, navigation or auto nav realign)

*
Position, latitude and longitude (lat/long)

*
North and east velocities

*
Heading (hdg)

*
Roll angle

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FMCS -FMCF INTERFACES -4

*
Altitude data

*
Ground speed data for air/ground logic.

CDU Inputs -Systems ARINC 629 Buses (L & R)
Each CDU receives flight plan synchronization data and brightness control data from the other CDUs. If both FMCFs failed, the flight plan synchronization data prevents flight plan map shifts when a CDU fails and the next CDU takes over. The brightness control input is from the local light sensors from each of the other CDUs and the PDS light sensors.
ASG Inputs -Systems ARINC 629 Bus (L and R)
The ASG function sends weight-on-wheels data to the CDUs. The CDUs use this data for the air/ground logic.
BPCU Inputs -Systems ARINC 629 Bus (L and R)
The BPCU sends primary and secondary power available data to the CDUs. The CDUs use this data for the air/ground logic.
OPAS Inputs -Systems ARINC 629 Bus (L and R)
The OPAS sends this data to the CDUs:
*
Captain navigation source select position (AUTO or CDU)

*
First officer navigation source select position (AUTO or CDU)

*
Heading reference switch position (NORM or TRUE).

AFDC Inputs -Systems ARINC 629 Buses (L and R)
The AFDS sends LNAV arm/operate data to the CDUs during the alternate LNAV guidance mode. The AFDS also sends an ILS tune inhibit to the left and right CDUs to stop manual tune requests to the ILS radios in approach.
AIMS Cabinet Inputs -Systems ARINC 629 Bus (L and R)
These functions in AIMS send data to the CDUs on the left and right systems ARINC 629 buses:
*
Central maintenance computing function (CMCF)

*
Primary display function (PDF)

*
Flight deck communication function (FDCF)

*
Flight management computing function (FMCF).

The CMCF sends this data to the CDUs:
*
Airplane identification

*
Flight leg

*
Flight phase

*
Date and time

*
Directed message commands

*
Operational software

*
Load commands

The PDF sends this data to the CDUs:
*
Brightness command

*
Display select panel (DSP) data

*
EFIS CP data.

EFFECTIVITY BEJ ALL  34-61-00 
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FMCS -FMCF INTERFACES -4

The FDCF sends a command to clear the scratchpad for the multi-functional display (MFD) text entry to the CDUs.
The FMCF sends this data to the left and right CDUs on the left and right system ARINC 629 buses:
*
Flight plan download

*
Radio tune download

*
Page displays.

The FMCF sends the same data on the left and right system buses to the center CDU when the left or right CDU fails.
AIMS also sends fuel switch position to the CDUs for use in air/ ground logic.
SDU Inputs -ARINC 429 Bus
The SDU sends communications data to the CDUs on a high speed ARINC 429 data bus.
PA/CI Controller Inputs -ARINC 429 Bus
The PA/CI controller sends passenger address and cabin interphone data to the center CDU for flight deck and cabin interface.
Analog Inputs
The CDUs receive lamp test and bright/dim inputs from the master/dim and test module.
　
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