(1)
The DAA power accepts 115 volt ac and 28 volt dc from circuit breakers to produce the dc voltages required for the processing of essential parameters.
(2)
The circuit includes a microcomputer whose function is to convert ARINC 429 bus information from the IRU to analog and discrete signals that are used by the pilot's instruments and other associated systems. The signals are pitch, roll and magnetic heading and the discretes that are valid signals associated with the attitude and heading information. The microcomputer consists of a processor, memories, controls, decoders, registers and other associated circuits. The microcomputer decodes the ARINC 429 input and, in an orderly routine, supplies the words to digital to analog converters (D/A) which convert the digital words into analog signals through the synchro transmitters. 26 volt ac is applied as reference to the D/As to perform the conversions.
(3)
The microcomputer also senses for status bits in the ARINC 429 format. When the IRU information is normal, the status bits are converted to valids through flag driver circuits.
Figure 11, Sheet 2 shows that part of the digital analog adapter (DAA) which processes the nonessential information from the IRU and the FMC.
(1)
The DAA power accepts 115 volt ac and 28 volt dc from circuit breakers to produce the dc voltages required for the processing of nonessential parameters.
(2)
The circuit includes a microcomputer whose function is to convert ARINC 429 bus information from the IRU and FMC to analog and discrete signals that are used by the pilot's instruments and other associated systems. The signals are pitch roll, magnetic heading and navigational parameters and the discretes that are valid signals associated with the parameter information. The microcomputer consists of a processor, memories, controls, decoders, registers and other associated circuits. The microcomputer decodes the ARINC 429 input and, in an orderly routine, supplies the words to digital to analog converters (D/A) which convert the digital words into analog signals. The analog signals are then converted into three wire ac signals through the syncrho transmitters or into two wire signal outputs. 26 volt ac is applied as reference to the D/As to perform the conversions.
(3)
The microcomputer also senses for status bits in the ARINC 429 formats. When the IRU and FMC information is normal, the status bits are converted to valids through flag driver circuits.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
L. Figure 11, Sheet 3 shows that part of the circuit in the digital analog adapter (DAA) which processes the nonessential information from the FMC and other sensors.
(1) The circuit includes a microcomputer whose function is to convert ARINC 429 bus information from the FMC to analog and discrete signals that are used by the pilot's instruments and other associated systems. The signals are N1 Limit Mode, N1 Bug Drive, VHF NAV/DME Frequency, and discretes. The microcomputer also converts analog inputs to ARINC 429 format for use by the FMC and FCCs. This information consists of VHF NAV/DME Frequnecy, VOR Omnibearing, VOR/LOC Deviation, DME L Distance, Total Fuel, and several discretes. The microcomputer consists of a processor, memories, controls, decoders, registers and other associated circuits.
8. IRS Master Caution Unit
_______________________
A. The master caution unit provides an interface between the IRS system and the airplane's master caution warning system.
B. The IRS master caution unit senses for inertial reference system (IRS) abnormal conditions and controls the IRS master caution light on the left side of the glareshield. The unit also supplies an input to the annunciator and dim module to operate the left and right master caution lights.
C. The unit is installed on the P10 panel near the aft end of the flight deck on the first officers side.
D. The unit contains four cards, one card each for monitoring ON DC, FAULT and DC FAIL Logics, from each IRU and one output card for control of the IRS caution light on the captains' side of the pilots' lightshield.
9. Attitude Director Indicator (ADI) (Fig. 12)
_________________________________
A. The attitude director indicator (ADI) is a multipurpose display instrument which displays pitch and roll attitudes to the pilots.
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