2. c. (4)
(5)
(6)
(7)
(e) HDG/STS selects heading or alignment
de~endinq
ur)onthe current IRU mode.
status for display,
Headinq is dis~la.yedin
degrees ~nd”tenths of degrees, and time-to-aiignment’completion
is displayed in minutes and tenths of minutes.
In the
alignment mode, the ISDU displays alignment status (time to NAV
ready) in the right display.
In the navigate mode, the ISDU
displays true heading in the left display. In the attitude
mode, the ISDU displays magnetic heading
in the left display
and ATT
in the right display.
Dimmer Knob
The dimmer knob is mounted on, and operates independently of, the
DSPL
SEL switch. As the dimmer knob is rotated clockwise, the
display brightens. As the dimmer knob is rotated counterclockwise,
the display dims.
Data Outputs
(a) The ISDU simultaneouslytransmits ARINC 429 low-speed (12.5
KBPS) initializationdata on three separately buffered digital
bus output
ports to ARINC 429 port no. 3 on each IRU.
(b) The data is BCD-transmitted upon manual command in a “burst”
mode of 2 to 4 transmissions within 2
seconds.
(c) Refer to table 2-8 for a list of the ARINC 429 data transmitted
from the ISDU to the IRU.
(d) Set heading data is accepted by the IRU only when in the
attitude mode.
Data Inputs
(a)
The ISDU receives navigation data from the IRU on the ARINC 429
high-speed digital data bus.
(b) Table 2-9 defines the ISDU input data and their
characteristics.
(c) All input data words, except the IRS
Discrete Word, 1abel 270,
are in BCD format.
(d) Table 2-10 defines the use and bit functions of the
IRS
discrete word (octal label 270) found
in table 2-9.
(e) Table 2-11 defines the use and bit functions of the Time-To-NAV
Ready discrete
word (octal label 351) found in table 2-9.
22-14-00
Page 127
Apr 15/93
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