1
GATE ECE 2002
Subjective
+5
-0
It is required to design a binary mod-5 synchronus counter using AB flip-flops such that the output Q2Q1Q0 changes as $$000 \to 001 \to 010$$ ........and so on. The excitation table for the AB flip-flops is given in the table GATE ECE 2002 Digital Circuits - Sequential Circuits Question 10 English 1 GATE ECE 2002 Digital Circuits - Sequential Circuits Question 10 English 2

(a) Write down the state table for the mod-5 counter.
(b)Obtain simplified SOP expressions for the inputs A2, B2, A1, B1, A0 and B0 in terms of Q2, Q1, Q and their complements.
(c) Hence, complete the circuit diagram for the mod-5 counter given in the figure using minimum number of 2-input NAND-gate only.

2
GATE ECE 1999
Subjective
+5
-0
The circuit diagram of a synchronous counter is shown in the figure. Determine the sequence of states of the counter assuming that the initial state is ‘000’. Give your answer in a tabulor form showing the present state QA(n), QB(n), QC(n), J-K inputs ( JA, KA, JB, KB, JC, K,) and the next state $${Q_{A\left( {n + 1} \right)}},\,{Q_{B\left( {n + 1} \right)}},{Q_{C\left( {n + 1} \right)}}$$ From the table, determine the modulus of the counter.
3
GATE ECE 1998
Subjective
+5
-0
The mod-5 counter shown in figure counts through states Q2 Q1 Q0 = 000, 001, 010, 011 and 100. GATE ECE 1998 Digital Circuits - Sequential Circuits Question 12 English

(a) Will the counter lockout if it happens to be in any one of the unused states?

(b) Find the maximum rate at which the counter will operate satisfactorily. Assume the propagation delays of flip-flop and AND gate to be tF and tA

4
GATE ECE 1997
Subjective
+5
-0
A sequence generator is shown in figure. The counter status (Q0 Q1 Q3) is intialized to 010 using preset/clear inputs.
The Clock has a period of 50ns and transitions take place at the rising clock edge.
(a) Give the sequence generated at Q0 till it repeats.
(b) What is the repetition rate for the generated sequence? GATE ECE 1997 Digital Circuits - Sequential Circuits Question 13 English
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