Digital Electronics - Engineering

Q1:

The counter shown in the given figure is built using 4 -ve edge triggered toggle FFs. The FF can be set asynchronously when R = 0. The combinational logic required to realize a modulo-13 counter is

A
F = Q4 Q3 Q2 Q1

B
F = Q4 + Q3 + Q2 + Q1

C
F = Q4 + Q3 + Q2 + Q1

D
F = Q4Q3Q2Q1

ANS:A -

F = Q4 Q3 Q2 Q1

Counter is modulo-13, it will count up to 15 but due to mod-13, it will be reset at 13, (13)10 = (1101 )2 = Q4 Q3 Q2 Q1.