AET Digital Electronics and Microprocessors 4 — Questions and Answers
Question 1: In a microprocessor-based avionics system, what is the primary function of the address bus?
- To carry data between the CPU and peripherals
- To specify the memory location or I/O device being accessed (Correct answer)
- To synchronize operations between the CPU and memory
- To provide power to memory chips
Correct answer: To specify the memory location or I/O device being accessed
The address bus carries the binary address output by the CPU to select a specific memory location or I/O device.
Question 2: Which logic gate produces a HIGH output only when all inputs are HIGH?
- OR gate
- NAND gate
- AND gate (Correct answer)
- NOR gate
Correct answer: AND gate
An AND gate output is HIGH only when every input is simultaneously HIGH.
Question 3: A D-type flip-flop in an avionics data register is clocked on the rising edge. What happens to the output Q when the clock transitions from LOW to HIGH?
- Q toggles regardless of D input
- Q takes on the value present at the D input at that moment (Correct answer)
- Q is reset to 0
- Q remains unchanged until the next falling edge
Correct answer: Q takes on the value present at the D input at that moment
On the rising clock edge, a positive-edge-triggered D flip-flop captures and transfers the D input value to Q.
Question 4: In ARINC 429 digital data bus, data words are transmitted:
- Simultaneously on 32 parallel lines
- Serially, one bit at a time on a differential pair (Correct answer)
- Via optical fiber at 100 Mbps
- As analog voltage levels on a single wire
Correct answer: Serially, one bit at a time on a differential pair
ARINC 429 uses serial transmission of 32-bit words over a shielded twisted-pair differential bus.
Question 5: What does the term 'interrupt latency' refer to in an avionics microprocessor system?
- The time required to program an interrupt vector table
- The delay between an interrupt request and the CPU beginning its service routine (Correct answer)
- The number of interrupts that can be queued simultaneously
- The voltage threshold that triggers an interrupt signal
Correct answer: The delay between an interrupt request and the CPU beginning its service routine
Interrupt latency is the elapsed time from when an interrupt is asserted until the CPU executes the first instruction of the interrupt service routine.
Question 6: A 4-bit binary counter has a modulus of:
- 4
- 8
- 16 (Correct answer)
- 32
Correct answer: 16
A 4-bit counter can represent 2^4 = 16 unique states (0 through 15), giving it a modulus of 16.
Question 7: Which Boolean expression correctly represents the output of an XNOR gate with inputs A and B?
- A ⊕ B
- NOT(A ⊕ B) (Correct answer)
- A · B
- A + B
Correct answer: NOT(A ⊕ B)
An XNOR gate is the complement of XOR, producing HIGH when inputs are equal: output = NOT(A ⊕ B).
AET Digital Electronics and Microprocessors 4
In a microprocessor-based avionics system, what is the primary function of the address bus?