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|  MIL-D-70789A (AR)
3.10.5 Data entry checking. All data received by the DRU
shall be tested for reasonableness before being accepted. Any
data outside the allowable range shall be rejected, and an Alert
indicated in a STATUS DATA message. Alert indications for
unreasonable data are listed below:
Parameter
Allowable Range
Alert Char/Bit
Easting
Allowable coordinates
D4/3, D5/2.
Northing
For Normal Zone,
Extended Zone, and
British National Grid.
Altitude
-1,000 to +10,000 meters
D4/4, D512
Zone (D7, 30.1.1)
1 to 60 (N/A when
D5/2
operating in British
National Grid).
Zone (D6, 30.1.1)
0 to 60 (N/A when
D5/2
operating in British
National Grid).
0
o
Latitude
- 7 5 to
+75 f
D4/3, D512
Longitude
-1800' to +1800'
D4/3, D5/2
The specific out of range data values which indicate parameters
are not being updated (see 3.5.7) shall not trigger an Alert.
Except for the command assigned to suppliers (30.2.12). the DRW
shall not accept any commands, data, (see 3.5.4.4.3.1) or changes
to the computer software except those specified herein.
3.10.6 Input Parameter verification.
3.10.6.1 Normal align. During Normal Align the DRU shall
accept and use any initialization parameters, input via the data
bus, which meet the reasonableness criteria of 3.10.5. Also, the
DRU shall perform an initial position reasonableness test. If
earth rate measurements indicate that the position used for
initialization is unreasonable or if instrument biases have
shifted to the extent that the values appear to be unreasonable,
bit 4 of ALERT DATA character D2 shall be set. In addition, bits
4 and 5 of STATUS character S1 shall be reset. If the alert
persists even when the initial parameters are correct, the proper
operator response will be to replace the DRU.
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