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Data Bus Systems and Protocols Flashcards

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  1. Which avionics data bus standard supports data rates up to 100 Mbps and is used in modern commercial aircraft such as the A380 and Boeing 787?

    Answer: ARINC 664 (AFDX)

    ARINC 664 Part 7 (AFDX) supports data rates up to 100 Mbps and is the high-speed backbone network used in the A380 and Boeing 787.

  2. What is the specified characteristic impedance of a MIL-STD-1553 bus cable?

    Answer: 70 ohms

    MIL-STD-1553 specifies a bus characteristic impedance of 70 ohms (±0.5 ohm) for the shielded twisted pair cable.

  3. When troubleshooting an ARINC 429 bus with no output signal, what should a technician check first?

    Answer: Power supply voltage to the transmitter LRU

    No signal on an ARINC 429 bus most commonly indicates a loss of power to the transmitter, so verifying power supply voltage is the logical first step.

  4. In MIL-STD-1553, what is a 'stub'?

    Answer: A short cable connecting a terminal to the main bus

    A stub is the short branch cable that connects a Remote Terminal or other device to the main MIL-STD-1553 bus cable, with maximum lengths defined by coupling type.

  5. What is the primary purpose of coupling transformers used in a MIL-STD-1553 bus installation?

    Answer: Provide electrical isolation and impedance matching between terminal and bus

    Coupling transformers provide galvanic isolation between the bus and each terminal while simultaneously matching impedance for proper signal integrity.

  6. What causes a parity error in an ARINC 429 data word?

    Answer: The total count of logic-1 bits in the 32-bit word is not odd

    ARINC 429 uses odd parity; a parity error occurs when the total number of 1-bits across the 32-bit word is even rather than odd, indicating a transmission error.

  7. Which tool is most appropriate for decoding and analyzing traffic on an ARINC 429 bus?

    Answer: ARINC 429 protocol bus analyzer

    An ARINC 429 bus analyzer decodes each 32-bit word into its label, data, SSM, and parity fields in human-readable format, making it the correct tool for protocol-level analysis.