The 28v dc hot battery bus also supplies power to the DEU 1 and DEU 2. This power is the hold up voltage. The DEU uses the hold up voltage to keep operation during power transients. The DEU can use the hold up voltage for a loss of the primary power of less than 2 seconds. If there is a loss of primary power for more than 2 seconds, the DEU does a shut down. After a shut down, it takes 90 seconds to start the DEU operation.
The DEU also uses the hold up voltage to do a shut down of the DEU processor. The DEU can have faults in random access memory or be in execution of a command when
737-600/700/800/900 TRAINING MANUAL
there is a loss of primary power. When a power loss occurs, the DEU uses the hold up voltage to store faults in nonvolatile memory and to do an orderly shut down of the processor. The DEU can use the hold up voltage for up to 10 seconds.
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P18-2 CIRCUIT BREAKER PANEL P6-1 CIRCUIT BREAKER PANEL CDS - POWER INTERFACES
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CDS -- PROGRAM PINS INTERFACE Program Pins
The display electronics units (DEU) and the display units (DU) have hardware program pins.
DEU Program Pins
These are the three types of program pins for the DEU:
-DEU position
-Airframe type
-Parity.
DEU position identifies the DEU as the left, right, or center unit. The 737 airplane only uses two DEUs. The DEUs are left or right.
Airframe type identifies the airplane type with the DEU.
The parity program pin identifies odd parity for the ARINC 429 data words. Odd parity identifies that each ARINC 429 data word has an odd number of data bits set to 1. A data word that does not have odd parity is not valid. For more information about parity see ARINC specification 429.
DU Program Pins
Each DU has different program pins set to ground. The program pins identify the DU location. These are the DU locations:
737-600/700/800/900 TRAINING MANUAL
-Left outboard (LOB) -Left inboard (LIB) -Upper center (UC) -Lower center (LC) -Right inboard (RIB) -Right outboard (ROB).
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DEU LEFT DEU CTR DEU RIGHT 737 747 757 767 PARITY (ODD)
DEU LEFT DEU CTR DEU RIGHT 737 747 757 767 PARITY (ODD)
DEU 1 DEU 2
A A A
B B B
C C C
D D D
E E E
LOB DU LIB DU UC DU RIB DU ROB DU
CDS - PROGRAM PINS INTERFACE
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737-600/700/800/900 TRAINING MANUAL CDS -- DISPLAY ELECTRONICS UNIT INTERFACES DEU Outputs
Each display electronics unit (DEU) has two graphics generator circuit card assemblies (GG CCA). Each GG CCA does a format of the display data and then transmits it to one of four coax couplers. Each GG CCA can make three formats so it can supply three displays at the same time.
The coax coupler is a one-to-six splitter. The six outputs of each coax coupler connect to each of the six display units (DU). This gives each DU an input from each GG CCA. The DUs monitor each input from the GG CCA but only show the data from one at a time.
Each DU has an address set by program pins for its location. When the DU receives image data from the DEU with the correct address that relates to its program pin discretes, it shows that image data (format) from the GG CCA.
ARINC 429 Status Bus
Each DU sends configuration and status data back to the DEUs on ARINC 429 status buses. This ARINC 429 status bus has this data:
-DU health data
-DU installation program pin data
-Remote light sensor (RLS) data
-Coax connection data.
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FROM L OUTBD DU
FROM L INBD DU
FROM UPR C DU
FROM LWR C DU
FROM R INBD DU
FROM R OUTBD DU COAX OUTPUT 1 GRAPHICS GENERATOR A
ARINC 429 STATUS BUS
COAX OUTPUT 2 GRAPHICS GENERATOR B
DEU 1
FROM L OUTBD DU COAX OUTPUT 2 FROM L
GRAPHICS INBD DU GENERATOR B
FROM UPR C DU ARINC 429 STATUS BUS
FROM LWR C DU COAX OUTPUT 1 GRAPHICSFROM R GENERATOR AINBD DU
FROM R OUTBD DU
DEU 2 COAX COUPLER 1
COAX COUPLER 2
COAX COUPLER 3
COAX COUPLER 4
ARINC 429 STATUS
L OUTBOARD DU
ARINC 429 STATUS
L INBOARD DU
ARINC 429 STATUS
UPPER C DU
ARINC 429 STATUS
LOWER C DU
ARINC 429 STATUS 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737-600/700/800/900培训手册 TRAINING MANUAL 2(3)
