(b)
Analog inputs 1) Analog signals from remote light sensors and external brightness controls
2) Analog discrete enable signals from software data loader, power enable, and test
(c)
Digital outputs
1) EIU status: low speed ARINC 429 bus
(d)
Analog outputs 1) Analog signals from the display units brightness/dimming
control circuitry 2) Analog discrete enable signals: none
B. EFIS/EICAS Interface Unit (Fig. 1, 2, 5, and 6)
(1)
The EFIS/EICAS Interface Units (EIUs) collect analog and digital signals from many airplane systems and forward selected data to the display units, CMCS, flight recorder, ACMS, and the FMCs. The main functions of an EIU are: signal input interface, data manipulation, signal output generation, and system monitoring. The EIU performs the master caution function and outputs to MAWEA for the aural tone function.
(2)
There are three EIUs located on the E2-6 rack. The EIUs are interchangeable, and each EIU is capable of supporting all six DUs with independent display formats. Each of the three EIUs process and transmit system interface data to the display units on three ARINC 429 high speed data buses. In normal operation, the left EIU provides EFIS data for the CAPT's PFD and ND. Also in normal operation, the left EIU provides engine and crew alerting data for the main EICAS and auxiliary EICAS, while the right EIU provides EFIS data for the F/O's PFD and ND. The center EIU is a spare. (Fig. 2)
(3)
The EIU source select switch on the EICAS control panel, and the EIU source select switches on the source select modules are normally in the AUTO position. (Fig. 5 and 6)
(4)
For the CAPT's EFIS and the EICAS, in the event of EIU failure, when the switches are in AUTO, the left, center, and right EIUs have first, second, and third priority, respectively, to automatically replace the faulty EIU. For the F/O's EFIS, in the event of EIU failure, when the switches are in AUTO, the right, center, and left EIUs have first, second, and third priority, respectively, to automatically replace the faulty EIU.
(5)
The EIU SEL switch on the EICAS control panel enables the main and auxiliary EICAS to be manually selected to an EIU. The manual selection of the EIUs will override any automatic switching.
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0 = OPEN1 = GND
EIU Source Selector Switch
Figure 5
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MAINTENANCE MANUAL
0 = OPEN 1 = GND
EICAS Control Panel Interface Figure 6
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(6)
The EIU utilizes 115 volts 400 hertz, single phase power. The electrical connections are made through an ARINC 600, 800 pin connector. The connector is located at the rear of the unit. Each EIU has program pins to identify EIU installation position, engine type, airplane model, and display options.
(7)
The EIUs incorporate BITE for self-checks and for monitoring abnormalities within the IDS. The EIUs then transmit the BITE data to the CMC. Each EIU transmits crosstalk data to the other EIUs over a high speed ARINC 429 data bus. This crosstalk provides input comparison validity.
C. EFIS Control Panel (Fig. 1)
(1) The EFIS control panel (EFIS CP) provides display control of the PFDs and the NDs. Two EFIS CPs are located on the P10 glareshield panel. In case of an EFIS CP failure, the CDU can function as an alternate EFIS CP. The following controls are provided on the EFIS CP:
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