AET Data Bus Systems and Protocols 1 — Questions and Answers
Question 1: What is the data transfer rate of ARINC 429 operating in high-speed mode?
- 12.5 kbps
- 100 kbps (Correct answer)
- 1 Mbps
- 10 Mbps
Correct answer: 100 kbps
ARINC 429 high-speed mode operates at 100 kbps, while its low-speed mode operates at 12.5 kbps.
Question 2: Which data flow topology best describes ARINC 429?
- Bidirectional multi-transmitter bus
- Unidirectional point-to-multipoint bus (Correct answer)
- Bidirectional command/response protocol
- Full-duplex ring topology
Correct answer: Unidirectional point-to-multipoint bus
ARINC 429 is a unidirectional bus where a single transmitter sends data to up to 20 receivers simultaneously.
Question 3: How many bits are contained in a standard ARINC 429 data word?
- 16 bits
- 24 bits
- 32 bits (Correct answer)
- 64 bits
Correct answer: 32 bits
An ARINC 429 data word is 32 bits long, consisting of an 8-bit label, SDI, data field, SSM, and a parity bit.
Question 4: What does the 8-bit 'label' field in an ARINC 429 word identify?
- The destination receiver address
- The type or parameter of data being transmitted (Correct answer)
- The identity of the source transmitter
- The error correction code appended to the word
Correct answer: The type or parameter of data being transmitted
The 8-bit label field identifies the type of data or avionics parameter (e.g., airspeed, altitude) contained in that word.
Question 5: Which encoding scheme is used by ARINC 429?
- Non-Return to Zero (NRZ)
- Manchester II Biphase
- Bipolar Return to Zero (BPRZ) (Correct answer)
- 4B/5B encoding
Correct answer: Bipolar Return to Zero (BPRZ)
ARINC 429 uses Bipolar Return to Zero (BPRZ) encoding with three voltage states: HIGH (+10 V), NULL (0 V), and LOW (−10 V).
Question 6: What is the maximum number of receivers that can be connected to a single ARINC 429 transmitter?
Correct answer: 20
A single ARINC 429 transmitter can drive up to 20 receivers on one unidirectional bus.
Question 7: What information does the SSM (Sign/Status Matrix) field provide in an ARINC 429 word?
- Signal synchronization timing
- Data sign and equipment operational status (Correct answer)
- Secondary system monitor readings
- Serial signal modulation type
Correct answer: Data sign and equipment operational status
The SSM field provides the sign of the numeric data and indicates the operational status (e.g., normal, failure warning) of the transmitting equipment.
