TM 1-1520-218-10
3C-187
Table 3C-102. System Failure Indications
SUBSYSTEM
FAILURE INDICATION
POSSIBLE EFFECTS
CDU Status
Bit 1
CDU Subsystem Status
CDU may be inoperative or have impaired capability.
Bit 2
MIL-STD -1553
Terminal
Status
CDU may be unable to communicate on the 1553 bus.
Bit 3 – 5
Expansion I/O Card Status
CDU may not be communicating on ARINC buses or
discrete interfaces; CDU keypad entry may also be
inoperative.
Bit 6
CDU Display Status
CDU display may be inoperative.
Bit 7
1553 CD Status
Not Used.
Bit 8
1553 AB Status
CDU may be unable to communicate on A and B
(primary FMB) buses.
Bit 9
Serial I/O Status
CDU may not be communicating on ARINC buses.
Bit 10
Discrete I/O Status
CDU may be unresponsive to discrete inputs or
incapable of generating discrete outputs.
Bit 11
Power Supply Status
CDU may be inoperative or have impaired capability.
Bit 12
Flash Memory Status
CDU
program
memory
may
be
incorrect
or
unavailable; OFP will cease to function. Bus control
relinquished.
Bit 13
NVM Status
CDU long-term memory (pilot entered data) may be
incorrect or unavailable.
Bit 14
ROM Status
CDU memory may be incorrect or unavailable. Bus
control relinquished.
Bit 15
RAM Status
CDU temporary memory may be incorrect or
unavailable; Bus control relinquished
Bit 16
CPU Status
CDU CPU may cease to function or have impaired
capability; Bus control relinquished.
BUS
MIL-STD -1553 Bus Status
NGO-A: CDU is not responding on the A bus.
NGO-B: CDU is not responding on the B bus.
NGO-T: CDU is not responding on either 1553 bus.
Data Loader Status
Bit 1-3
Not Used
Bit 4
Terminal Address Failure
Data Loader is unable to respond on the 1553 bus.
Bit 5
Fail – Safe Timer Fail
Data Loader processor has ceased to process 1553
data; 1553 data transmission terminated.
Bit 6
Memory Checksum Failure
Data Loader program memory may be incorrect or
unavailable; OFP may cease to function.
Bit 7
Not Used
Bit 8
RAM Memory Failure
Data Loader program memory may be incorrect or
unavailable.
Bit 9
Not Used
Bit 10
LSI Fault
Data Loader 1553 circuitry failed; 1553 data
transmission terminate.
Bit 11
Transmit B Bus
Data Loader has failed to transmit data on the 1553 B
bus.
