AET Digital Electronics and Microprocessors 2 — Questions and Answers
Question 1: An ADC (Analog-to-Digital Converter) performs which conversion in avionics systems?
- Converts digital signals to analog signals
- Converts analog signals to digital signals (Correct answer)
- Converts AC voltage to DC voltage
- Converts binary to hexadecimal notation
Correct answer: Converts analog signals to digital signals
An ADC samples continuous analog sensor data and converts it to discrete digital values for processing by a microprocessor.
Question 2: The ARINC 429 data bus used in commercial aviation is best described as a:
- Multi-transmitter, multi-receiver bidirectional bus
- Single-transmitter, multiple-receiver unidirectional bus (Correct answer)
- Multi-transmitter, single-receiver unidirectional bus
- Bidirectional point-to-point serial bus
Correct answer: Single-transmitter, multiple-receiver unidirectional bus
ARINC 429 uses a unidirectional architecture with one transmitter driving up to 20 receivers on a twisted-pair wire.
Question 3: What does CRC stand for in the context of digital data communications?
- Cyclic Redundancy Check (Correct answer)
- Clock Rate Control
- Circuit Reset Command
- Carrier Reference Clock
Correct answer: Cyclic Redundancy Check
CRC (Cyclic Redundancy Check) is an error-detection algorithm that generates a checksum to verify data integrity during transmission.
Question 4: How many discrete digital output values can a 12-bit ADC produce?
- 1,024
- 2,048
- 4,096 (Correct answer)
- 8,192
Correct answer: 4,096
A 12-bit ADC can represent 2^12 = 4,096 discrete digital values, ranging from 0 to 4,095.
Question 5: PWM (Pulse Width Modulation) is used in avionics primarily to:
- Modulate radio carrier frequencies
- Control motors and actuators by varying the duty cycle (Correct answer)
- Synchronize multiple ARINC data buses
- Provide power line communication between LRUs
Correct answer: Control motors and actuators by varying the duty cycle
PWM controls the average power delivered to motors and actuators by varying the on-time (duty cycle) of a fixed-frequency digital pulse.
Question 6: Which type of data transmission sends bits one at a time sequentially over a single channel?
- Parallel transmission
- Serial transmission (Correct answer)
- Synchronous burst transmission
- Multiplex transmission
Correct answer: Serial transmission
Serial transmission sends data bit-by-bit over a single wire, as used in avionics buses like ARINC 429 and RS-232.
Question 7: What is the output of an XOR gate when both of its inputs are logic HIGH?
- HIGH
- LOW (Correct answer)
- Undefined — depends on propagation delay
- Depends on the clock signal
Correct answer: LOW
An XOR (Exclusive OR) gate outputs LOW when both inputs are the same state (both HIGH or both LOW).
AET Digital Electronics and Microprocessors 2
An ADC (Analog-to-Digital Converter) performs which conversion in avionics systems?