6. B.
(1) DC-884 Display Controller Interface
The DC-884 Display Controllers provide all mode and PFD, ND, and
EICAS display format select information. The symbol generators
utilize the DC-884 for control of the PFD and ND formats as follows:
PFD/ND Source
Display Controller
SG1 DC1
SG2
DC2
SG3
DC1 or DC2
The symbol generators utilize both display controllers on an equal
priority basis for control of the EICAS formats except for
selections for the system page, Vspeeds from the FLT REF menu, FWC,
DAU and AT selections.
For these exceptions, the symbol generators
only look at DC No. 1 (DC No. 1 retransmits DC No. 2 data on ASCB).
If
power is lost to DC1, then the SGS will utilize DC No. 2.
(2) FC-880 Fault Warning Computer Interface
The FC-880 Fault Warning Computers provide all data necessary for
the caution advisory portion of the EICAS. This data is provided in
an ASCII form over the ASCB. The fault warning computer provides up
to 24 messages for display with up to 18 characters per message.
The FWC also provides the necessary data to display checklist
information, as well as exceedance displays.
The DC-884 Display Controller defines which fault warning computer
is utilized for display purposes. The symbol generators monitor the
fault warning computers through comparison of checksums transmitted
by each fault warning computer. A detected fault warning computer
miscompare (red messages only) is displayed on the PFD as an amber
FWC.
(3) DA-884 Data Acquisition Unit Interface
The DA-884 Data Acquisition Units provide radio altitude and all
engine and aircraft system parameters.
The data acquisition unit broadcasts its data field simultaneously
on both ASCB A and ASCB B. The pilot controls which channel is
displayed by the display controller’s SENSOR mode. The symbol
generator will disregard the channel of the data acquisition unit
not selected for display. Comparison monitoring of the two data
acquisition unit channels shall be accomplished by the fault warning
computers.
22-14-00
Page 158
Apr 15/93
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