Table of Contents
“Counter is to count the number of electrical pulses.” To count certain events electrical pulses proportional to the number of events are generated for counting digital counter consists of flip flops .
There are two types –
1. Asynchronous – ( Ripples counter)
Shown a counter build with JK flip flop J and K input connected always in High Voltage so each flip flop become toggle mode when clock pulse in falling edge.
When CLR is high then all output means Q become reset.
Q = 0 0 0 0
and CLR is made Low than counter is ready to work. All the J and K input of J K flip flop kept high then flip flop will toggle Mode.
(I) 1st following edge of clock pulse first JK flip flop working and toggle so the output Q0 = 1 and same at time 2nd JK flip flop working but their previous input Q0 = 0 so Q1 =0 similarly same work in next ff so output.
Q = 0 0 0 1
(II). When the second Pulse falling edge again 1st JK ff toggle so Q0 = 0 and second flip flop find falling edge through Q0 = 1 (previous) in this case change the values falling edge so second ff become toggles so the output.
Q = 0010
(III) When the third falling edge first FF become toggle so q0 = 1 and the change of value q0 = one so it is rising edge so second ff not work in this case so Q 2 = 1 then
Q = 0 0 1 1
(IV) When 4 th falling edge first ff become toggle Mode q0 = 0, now second ff q0 change means it is falling edge for second ff so second ff become toggle so q 1 = 0 , then for third ff : q 1 value change 1 to 0 means falling adge so 3rd ff become Toggle so we get Q2 = 1 for 4th ff : q = 0 .
It is rising adge so not work 4 rth ff.
q = 0100 .
8 1 0 0 0
Synchronous counter (Parallel counter) –
“In an asynchronous counter all flip flops are clocked simultaneously, these are faster then asynchronous counter due to simultaneous clocking of flip flops .