TM 1-1510-218-10
3C-54
Figure 3C-22. FMS-800 Simplified Diagram
The data cartridge is used to load mission data
and to act as an in-flight library of ICAO waypoints. It
also loads the current worldwide magnetic variation
tables automatically upon power-up and can be used
to load or store GPS almanac data to reduce GPS cold
start time following installation of a GPS receiver.
NOTE
A lithium battery is installed in the CDU to
reduce the initialization time.
The MIL-STD-1553B multiplexed serial digital
data bus is the primary means of control and data
Transferal within the FMS-800. This bus has the
following characteristics.
(a) Dual data paths (buses) between
each remote terminal and the bus controller.
(b) No operator actions required for
initialization or any other aspect of normal bus
controller operation.
The CDU operates on the MIL-STD -1553B data
bus as a Bus Controller (BC). The CDU that is
functioning as bus controller performs all navigation
and guidance computations, builds all page displays,
communicates with all external equipment and
performs all other computations required to support
FMS-800 operation.
b. CDU Operations.
(1) General Operation Concepts. CDU data
entry
operations
are
performed
with
a
full
alphanumeric keypad, arrow keys, function keys, and
eight line select keys, Figure 3C-23. The CDU display
has 8 lines of 22 characters each. Lines 1, 3, 5, and 7
are data lines with a line select key on both the right
and left of the field. Line 2 is reserved for page title
and line 6 is reserved as an annunciation line. Line 4
is an unreserved data line and line 8 is the scratchpad
for holding all keypad entries. See Table 3C-13 for the
descriptions of the CDU’s function and application
keys.
NOTE
The character set displayed in Figure 3C-23
does not represent the actual view on the
CDU screen.
