757 AMM 飞机维护手册 仪表 CHAPTER 31 - INSTRUMENTS 2(37)

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 5)  A Take-off Thrust discrete is sent to the WEU for T/O configuration warning. This discrete is set to ground when engine thrust exceeds a fixed value and the thrust reversers are stowed properly.
 (b) Digital Outputs 1) Once display format logic determines the data that is to be displayed. An ARINC 429 transmitter converts this data into serial data words. The data is then transmitted to other airplane systems.
 2)  Both left and right EICAS computers have two low speed ARINC 429 digital output ports. One bus is connected to the related left or right FMC to provide the FMC with fuel flow data. The other port is connected to a general EICAS output bus. All unused 429 inputs of the EICAS computers are connected to their respective (left or right) output bus. This wraparound is essential to proper software operation.
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 (c)
(d)
A
757 MAINTENANCE MANUAL
 3)  A hi-speed ARINC 429 data bus is connected from the left EICAS computer to the right and one from the right EICAS computer back to the left.
 4)  A hi-speed ARINC 429 bus is connected from each computer to the bottom display switching module. A single data bus is then connected from this switching module to the DFDAU. The DFDAU will be switched to receive data from only the computer that is currently providing information to the EICAS display units.
 5)  GUN 102, 103; The data sent to the DFDAU is also sent to a data tap on a test connector in the P61 panel. Data can be collected through the test connector using external support equipment.
 6)  All digital outputs transmitted are also internally fed back into 429 receivers. This internal wraparound is used by BITE for failure detection.
Data Display
 1)  Analog discretes are received by each computer from the top and bottom display units. These discretes indicate a display unit failure. When received, the caution discrete logic will generate a level C message EICAS CRT. The display format logic uses Display Unit fail information to establish proper display states.
 2)  Once the proper display states have been selected, instructions are sent to the display controller. The display controller also receives commands from the display generator file. The display controller uses these instructions to control the video/timing generator and display sequencers.
 3)  The video/timing generator provides red, green, and blue color signals, strobe intensity, beam test, and video sync signals to both top and bottom display units. The display sequences provide signals to stroke generators, which in turn control the X and Y display drivers. The display drivers then provide X-deflection and Y-deflection signals to drive both top and bottom display units.
Analog Signal Outputs
 1)  Each EICAS computer provides 16 analog signal outputs for driving the color CRTs of the display units. Six video and two deflection signals from the left and right computers are sent to the top display switching module. Eight signals from the left computer and eight more from the right are also routed to the bottom display switching module.
　
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