AET Data Bus Systems and Protocols 2 — Questions and Answers
Question 1: Which protocol architecture is used by MIL-STD-1553?
- Unidirectional broadcast
- Command/response with time division multiplexing (Correct answer)
- Carrier-sense multiple access (CSMA)
- Token-passing ring
Correct answer: Command/response with time division multiplexing
MIL-STD-1553 uses a command/response, time division multiplexing protocol managed by a Bus Controller that polls all Remote Terminals.
Question 2: What is the fixed data transfer rate of MIL-STD-1553?
- 100 kbps
- 1 Mbps (Correct answer)
- 10 Mbps
- 100 Mbps
Correct answer: 1 Mbps
MIL-STD-1553 operates at a fixed data rate of exactly 1 Mbps.
Question 3: How many Remote Terminals (RTs) can be addressed on a single MIL-STD-1553 bus?
- 16
- 31 (Correct answer)
- 64
- 128
Correct answer: 31
MIL-STD-1553 uses 5-bit RT addressing, which allows 32 addresses; however, address 31 is reserved for broadcast, leaving 31 usable RT addresses.
Question 4: What is the role of a Bus Monitor (BM) in a MIL-STD-1553 system?
- Issues commands to Remote Terminals
- Passively records all bus traffic without transmitting (Correct answer)
- Acts as a standby Bus Controller
- Arbitrates access conflicts between RTs
Correct answer: Passively records all bus traffic without transmitting
A Bus Monitor passively listens to and records all MIL-STD-1553 bus traffic for analysis or logging without participating in transactions.
Question 5: ARINC 664 Part 7 (AFDX) is derived from which commercial networking standard?
- Token Ring (IEEE 802.5)
- ATM (Asynchronous Transfer Mode)
- Switched Ethernet (IEEE 802.3) (Correct answer)
- FDDI (Fiber Distributed Data Interface)
Correct answer: Switched Ethernet (IEEE 802.3)
AFDX (Avionics Full-Duplex Switched Ethernet) is based on switched Ethernet (IEEE 802.3) with deterministic enhancements for avionics use.
Question 6: What AFDX mechanism ensures deterministic, guaranteed bandwidth for each avionics data stream?
- Token passing protocol
- Virtual Links with Bandwidth Allocation Gaps (BAGs) (Correct answer)
- Priority queuing with preemption
- Quality-of-Service DSCP marking
Correct answer: Virtual Links with Bandwidth Allocation Gaps (BAGs)
AFDX uses Virtual Links (VLs), each with a defined Bandwidth Allocation Gap (BAG), to guarantee deterministic delivery for every data stream.
Question 7: Which signal encoding scheme does MIL-STD-1553 use?
- Bipolar Return to Zero (BPRZ)
- Manchester II Biphase (Correct answer)
- Non-Return to Zero Level (NRZ-L)
- 8B/10B encoding
Correct answer: Manchester II Biphase
MIL-STD-1553 uses Manchester II Biphase encoding, which provides a mid-bit transition that allows clock recovery from the data signal.
AET Data Bus Systems and Protocols 2
Which protocol architecture is used by MIL-STD-1553?