ISCET Digital Electronics Principles 5

Question 1

Which type of logic circuit has outputs that depend only on present inputs, with no memory?

Accepted Answer

Combinational circuit

Answer

Combinational circuits have no feedback or storage; outputs are determined solely by the current input combination.

Question 2

What is the purpose of a priority encoder?

Accepted Answer

Outputs the binary code of the highest-priority active input

Answer

A priority encoder resolves simultaneous inputs by outputting the binary address of the highest-priority (typically highest-numbered) active input.

Question 3

In synchronous sequential circuits, what ensures all flip-flops change state at the same time?

Accepted Answer

A common clock signal

Answer

A shared clock signal drives all flip-flops simultaneously, making the circuit synchronous and predictable.

Question 4

Which BCD encoding assigns weights 8-4-2-1 to the four bit positions?

Accepted Answer

Natural BCD (8421)

Answer

Natural BCD (8421) assigns positional weights 8, 4, 2, 1 from MSB to LSB, directly representing decimal digits 0–9.

Question 5

What causes a race condition (hazard) in combinational logic?

Accepted Answer

Unequal propagation delays causing momentary incorrect output glitches

Answer

A logic hazard occurs when signal paths through a circuit have unequal delays, producing brief spurious output transitions.

(ISCET) International Society of Certified Electronics Technicians Practice Test