*
CMCF fault history database synchronization

*
Central maintenance source switching

*
Offside CMCF data access.

After power-up, if both the CMCFs are operational then the primary CMCF is the left CMCF. The secondary CMCF is the right CMCF. The primary CMCF controls all the CMCF outputs to the airplane systems. The right CMCF becomes the primary CMCF if the left CMCF fails or if changed by the central maintenance source switching selection on the MAT.
The CMCFs do configuration checks continuously after a power-up. During dual operation, the CMCFs do configuration checks for these:
*
Operational program configuration files (OPC)

*
Operational program software (OPS)

*
Airline modifiable information (AMI)

*
Fault history databases

*
Manual flight leg enabled/disabled condition.

In case of a configuration check difference between the two CMCFs, the CMCF shows a warning dialog box on the MAT.
For different AMIs between the two CMCFs, the CMCFs:
*
Record a shop fault message

*
Generate a fault report

*
Continue to operate normally.

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CMCS -FUNCTIONAL DESCRIPTION

The primary CMCF automatically cross loads the flight leg enabled/disabled condition to the secondary CMCF when the two CMCFs manual flight leg enable/disable conditions are different.
The CMCF supplies an automatic way to maintain an identical fault history database in both CMCFs at all times. The primary CMCF cross loads the fault history database to the secondary CMCF automatically whenever the two databases are different. The primary CMCF cross loads the fault history database in 1 minute.
The primary CMCF can be switched from one CMCF to the other CMCF. The MAT supplies the central maintenance source switching operation. The central maintenance source switching is inhibited during these conditions:
*
Ground tests operation

*
Data load operation

*
One CMCF failure

*
Onboard engine balancing system operation.

Each CMCF gets data from the other CMCF for input monitoring and reports from the AIMS intercabinet buses.
CMCF BITE

Each CMCF has BITE which detects any CMCF software partition failures. A CMCF fails if the CMCF BITE detects one of these:
EFFECTIVITY
BEJ ALL

*
Bad data tables

*
Loss of maintenance message correlation to flight deck effects (FDEs)

*
Bad stored fault history database

*
Loss of MAT and PMAT communications.

The CMCF BITE records a shop fault message when a failure occurs. After a CMCF failure, the failed CMCF if in control, loses control to the offside CMCF. The offside CMCF becomes the primary CMCF.
Single CMCF Power-up Configuration Checks
Each CMCF does configuration checks during power-up or after the software load of an OPS, OPC, data table, or airline database. The CMCF does configuration checks for an:
*
Invalid or missing OPC

*
Invalid or missing OPS

*
OPC that is incompatible with the OPS

*
Invalid or missing AMI

*
AMI that is incompatible with the OPS.

If a configuration check finds a failure the CMCF records a shop fault message. The CMCF also shows a warning dialog box for each failure.
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CMCS -FUNCTIONAL DESCRIPTION

Single and Dual Hardware Power-up Failures

The CMCFs check for hardware failures at power-up. A failure indication, R CMCF or L CMCF Initialization Failed, shows on the MAT if one of the CMCFs has a hardware failure at power-up. The CMCF also records a shop fault message. The CMCF with no failures is the primary CMCF and supplies the CMCF outputs.
If both CMCFs have hardware failures at power up, Initialization Failed shows on the MAT. The CMCFs record a shop fault message.
Fault Data Processing
The CMCF fault processing sub-function:
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Processes inputs

*
Inhibits invalid fault reports

*
Creates limited fault reports

*
Removes cascaded effects of failures

*
Correlates FDEs and maintenance messages

*
Stores FDEs and maintenance messages.

Loadable Diagnostic Information

The CMCF requests data from the loadable diagnostic information (LDI) to operate. The LDI contains:
*
Fault data

*
FDEs data

*
MOs data

*
Maintenance page snapshots (MPSs) data

*
Fault correlation algorithms
　
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