(d)
Each EICAS computer receives high speed ARINC 429 data from the maintenance control display panel (MCDP) and from the other EICAS computer over a crosstalk bus. The crosstalk buses are used to share uniquely received parameters, as well as to compare parameters received by both computers for BITE disagreement checks.
(e)
All unused input ports on the left computer are tied to an output EICAS wraparound bus from the left computer. The right computer operates the same way.
Analog Signal Inputs (Fig. 9)
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MAINTENANCE MANUAL
ANALOG INPUT PORT TYPES
HARDWARESOFTWARE
DC VOLTS PORT
VARIABLE
DC VOLTS - VOLTAGE QUANTITY READ DIRECTLY, AS IN THE CASE OF BATTERY VOLTAGE, ORIN PROPORTION TO ANOTHER QUANTITY, SUCH AS APU OIL QUANTITY, OR BRAKE TEMPERATURE.
COMMON REF GROUNDDC VOLTS
5V DC
DC RATIO - DETERMINES % OPENING OF VALVE OR DOOR BY RATIO OF DC VOLTAGES.PWR SUP
EXAMPLES: RAM OUT DOOR, TRIM VALVE.
RATIODISCRETE - ANALOG SIGNAL INDICATES COMPONENT OR SYSTEM STATUS CHANGE.
DC RATIO PORT
VARIABLE
LOGIC EXAMPLES: IDG TEMP RISE SWITCH, ENG TAI, BK TEMP WARN, THRUST REVERSER IN TRANSIT.
DISCRETE
TEMP BULB - RESISTANCE MEASUREMENT FOR TEMPERATURE. USED TO MEASURE TEMPERATURESDC RATIO
IN COMPARTMENTS, HEAT EXCHANGER INLETS AND OUTLETS, OIL TEMPERATURE.TEMP BULBPORT V REF RESTHERMOCOUPLE - USED TO MEASURE EXHAUST GAS TEMPERATURE (EGT).
LOGIC
VARIABLE DC DIFF - MEASURES VOLTAGE DIFFERENCE ACROSS A SET RESISTANCE. USED FOR BATTERYEGT PORT CURRENT OUTPUT MEASUREMENT, ALSO FOR CREW OXYGEN PRESSURE.
THERMO-T EGT
TEMP BULB
COUPLE
A/D
FREQ/AC VOLTS - MEASURES FREQUENCY AND AC VOLTS UTILIZING INTERNAL EICAS COUNTERSCOLD JUNCTION
T REF
AND RECTIFIERS USED FOR ELECTRICAL POWER BUS INDICATION.TEMPERATURE
DC DIFF PORT A. - MEASURES AC PHASE DIFFERENCE FROM SYNCHRO TRANSMITTERS TO DETERMINE POSITION
VARIABLE EICAS
CHANGE OF AILERONS, RUDDER, ELEVATORS.DISPLAYS PULSE - FUEL FLOW IS MEASURED BY A FUEL FLOW TRANSMITTER, WHICH CONVERTS THE FUELDC DIFF
FLOW RATE TO ELECTRICAL PULSE SIGNALS. EICAS MEASURES THE START AND STOP TIMES OF
AC REF RECTIFIER
THE PULSES TO DETERMINE FLOW RATE.AC
RATIO
RATIO
LOGIC TACHOMETER - COIL MEASURES RPM TURNING RATE OF ROTORS N1,N2, AND N3.
VARIABLE
PORT RECTIFIER
PHASE DET
(SIGN OF .)
ANGLEAC SINGLE
AC .
PORT
LOGIC
VARIABLE
PHASE
RECTIFIER
AC VOLTS
PORT
VARIABLE
RECTIFIER
AC FREQ PORT
FREQUENCYPULSE
COUNTER
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