(b)
The EICAS display select panel does not monitor itself. In case of failure the EICAS computers will detect a loss of data or invalid data from the display select panel.
(c)
The EICAS computer is divided into three subsystems for BITE self-monitoring purposes. These subsystems are input/output (I/O ) interface, central processing unit (CPU) and display generator. The three subsystems detect faults in each other by means of a heartbeat monitor. If any one of the three subsystems stops, all activity in the other two subsystems stops also.
(d)
If the I/O interface, CPU, and display generator subsystems are all functioning properly, the CPU then monitors and analyzes the system in the following areas: 1) It tests itself, the program memory, scratch pad memory,
and non-volatile memory.
2) It detects sensor input values that are out of range, and ARINC 429 sensors that are not transmitting frequently enough.
3) It exchanges sensor data that is received by both computers with that of the other computer. It does this in order to isolate the device responsible for invalid sensor data.
4) It confirms that all discrete and ARINC 429 output transmitters are operating correctly. It does so by comparing the value sent with the value read from receivers connected to each transmitter.
5) It monitors the power supply voltages used by the I/O interface.
6) It isolates display faults to the computer or a display unit by analyzing the data supplied by the display generator.
7) It monitors an over-temperature indication from the power supply.
(e) Once BITE has detected an abnormality in the system, EICAS will respond in one of the following ways: 1) For a detected display unit problem, the affected display
is shut down or blanked. The level C message EICAS DISPLAY will be displayed on the remaining display unit.
2) If either computer detects invalid or loss of data from the display select panel, the computers revert to the full up mode display. In addition, the level C message EICAS CONT PNL is displayed.
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31-41-00
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3)
4)
5)
A
757
MAINTENANCE MANUAL
For a detected fault in a computer that affects in-flight
operation of the system, the faulty computer is shut down.
Display switching to the right computer is accomplished if
the left computer has failed and the computer select switch
is set to AUTO. The status message L EICAS CMPTR or R
EICAS CMPTR, as applicable, is generated for display when
selected.
If an invalid or improper program pin configuration is
detected at power up, the system will respond by blanking
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