Digital Electronics/Circuits Multiple Choice Questions on “Counter ICs”.
1. What is the difference between a 7490 and a 7493?
A. 7490 is a MOD-10, 7493 is a MOD-16
B. 7490 is a MOD-16, 7493 is a MOD-10
C. 7490 is a MOD-12, 7493 is a MOD-16
D. 7490 is a MOD-10, 7493 is a MOD-12
Answer: A
Clarification: The difference between a 7490 and a 7493 is that 7490 is a MOD-10, 7493 is a MOD-16 counter. Thus, 7490 traverses 10 states and 7493 traverses 16 states.
2. How many different states does a 2-bit asynchronous counter have?
A. 1
B. 4
C. 2
D. 8
Answer: B
Clarification: For a n-bit counter, total number of states = 2n. Thus, for 2-bit counter, total number of states = 22 = 4.
3. A 12 MHz clock frequency is applied to a cascaded counter containing a modulus-5 counter, a modulus-8 counter, and a modulus-10 counter. The lowest output frequency possible is ________
A. 10 kHz
B. 20 kHz
C. 30 kHz
D. 60 kHz
Answer: C
Clarification: Cascaded counter containing a modulus-5 counter, a modulus-8 counter, and a modulus-10 counter. So, 5*8*10=400. Applied clock frequency = 12 MHz; hence, the lowest output frequency possible is 12MHz/400=30 kHz.
4. Which one is a 4-bit binary ripple counter?
A. IC 7493
B. IC 7490
C. IC 7491
D. IC 7492
Answer: B
Clarification: IC 7493 is a 4-bit binary ripple counter. It is a MOD-16 counter with 24 = 16 states.
5. IC 7493 consist of ____________
A. 4 S-R flip-flop
B. 4 J-K flip-flop
C. 4 master-slave flip-flop
D. 4 D flip-flop
Answer: C
Clarification: IC 7493 consist of 4 J-K master-slave flip-flop. It is a MOD-16 counter with 24 = 16 states.
6. A reset input is used in IC 7493, why?
A. For increment of bit by 1
B. For decrement of bit by 1
C. For reset the counter
D. For setting the counter
Answer: C
Clarification: The reset inputs are used to reset the counter to 0000.
7. In a 4-bit binary ripple counter, four master-slave flip-flops are internally connected to provide a ________ bit counter.
A. Divide-by-2 & divide-by-6
B. Divide-by-6 & divide-by-8
C. Divide-by-2 & divide-by-8
D. Divide-by-4 & divide-by-8
Answer: C
Clarification: In a 4-bit binary ripple counter, four master-slave flip-flops are internally connected to provide a Divide-by-2 & divide-by-8 bit counter.