Asynchronous and Synchronous Flip Flop Inputs (reset and set)

Synchronous Inputs

                               Normally asynchronous inputs are referred as control inputs, the flip flop changes it state in synchronization with clock inputs.
 Therefore the synchronous inputs are use with with clock signal to produce flip flop.

  Example  input D and T in D and T flip flop respectively etc 

D Flip Flop                                                                                               T Flip Flop

 

                                           

Asynchronous Inputs

                                   These are the inputs which effect the output of flip flop independent of synchronous inputs and clock input.These can be use to set the output of flip flop to "0" or "1" state regardless of the condition of other inputs.
 Asynchronous inputs are override inputs,since they can be used to override the output of flip flop to one state or another.

Example set and reset input

              When the set input is activated, the flip-flop will be set (Q=1, not-Q=0) regardless of any of the synchronous inputs or the clock.
 When the reset input is activated, the flip-flop will be reset (Q=0, not-Q=1), regardless of any of the synchronous inputs or the clock. 
In order to run an IC of flip flop the set and reset inputs either active low or active high to run output of flip flop.
If the SET and RESET are active high a positive input of 3 to 5 volt should be given to them and in case of active low ground them. 
                                                            AS in IC 74HC74
  
pin 1 and 13 asynchronous reset-direct input (active LOW)
pin 4 and pin 10 asynchronous set-direct input (active LOW)

The set and reset are initially use to clear the memory of flip flop and then these both are grounded to get output signal of flip flop in synchronization with the synchronous inputs and clock input.