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TRIGGERING OF FLIP-FLOPS

TRIGGERING OF FLIP-FLOPS FLIP - FLOPS CHANGE STATE ONLY WHEN A CLOCK SIGNAL IS PRESENT. CLOCK SIGNAL IS NOT NECESSARILY INSTANTANEOUS SO THERE NEEDS TO BE A WAY TO PREVENT THE FLIP-FLOP FROM CHANGING STATE MULTIPLE TIMES DURING A CLOCK CYCLE. 2 WAYS TO ACHIEVE THIS :

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TRIGGERING OF FLIP-FLOPS

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  1. TRIGGERING OF FLIP-FLOPS • FLIP - FLOPS CHANGE STATE ONLY WHEN A CLOCK SIGNAL IS PRESENT. • CLOCK SIGNAL IS NOT NECESSARILY INSTANTANEOUS SO THERE NEEDS TO BE A WAY TO PREVENT THE FLIP-FLOP FROM CHANGING STATE MULTIPLE TIMES DURING A CLOCK CYCLE. • 2 WAYS TO ACHIEVE THIS : • ONLY CHANGE STATE ONCE THE CLOCK CYCLE IS FINISHED. THIS TYPE OF FLIP-FLOP IS CALLED A MASTER – SLAVE FLIP-FLOP. • ONLY TRIGGERS DURING A SIGNAL TRANSITION. THIS TYPE IS CALLED AN EDGE - TRIGGERED FLIP-FLOP.

  2. Master Slave S Q R Q’ S Q R Q’ SCR Q Q’ MASTER - SLAVE FLIP - FLOPS • A pulse-triggered flip-flop consists of two latches, one acts as a master and the other acts as a slave. • Master-slave flip-flop allows one flip-flop to change state as the clock pulse is active. • Output from one flip-flop goes into another flip-flop, which is attached to an inverted clock input. State of the first flip-flop settles by the time its output changes the state of the second flip-flop after the clock pulse has finished and stable output is achieved. MASTER LATCH WORKS WHEN C = 1 SLAVE LATCH WORKS WHEN C = 0

  3. RS MASTER - SLAVE FLIP - FLOPS MASTER SLAVE RS FLIP-FLOP IS ONLY USED IN APPLICATIONS WHERE IT IS GUARANTEED THAT BOTH R AND S CANNOT BE LOGIC 1 AT THE SAME TIME.

  4. JK MASTER - SLAVE FLIP - FLOPS MASTER SLAVE AS BEHAVIOR OF JK FLIP-FLOP IS COMPLETELY PREDICTABLE UNDER ALL CONDITIONS,SO IT IS PREFERRED TYPE OF FLIP-FLOP FOR MOST LOGIC CIRCUIT DESIGNS.

  5. EDGE TRIGGERED FLIP - FLOPS • AN EDGE - TRIGGERED FLIP - FLOP IS A BISTABLE DEVICE WHOSE STATE DEPENDS ON THE SYNCHRONOUS INPUTS EITHER AT THE POSITIVE EDGE OR AT THE NEGATIVE EDGE OF A CLOCK PULSE. • EDGE TRIGGERED FLIP – FLOPS TRIGGER ONLY WHEN THE PULSE IS IN TRANSITION. • SOME TRIGGER DURING A POSITIVE TRANSITION ( 0 – TO - 1) CALLED POSITIVE EDGE TRIGGERED FLIP - FLOPS. OTHERS TRIGGER DURING A NEGATIVE TRANSITION ( 1 – TO – 0 ) CALLED NEGATIVE EDGE TRIGGERED FLIP - FLOPS.

  6. POSITIVE EDGE - TRIGGERED D FLIP - FLOP S Q CLK Q R D

  7. D FLIP - FLOP USING NOR LATCHES

  8. J Q CLK Q K POSITIVE EDGE - TRIGGERED JK FLIP - FLOP

  9. SUMMARY FLIP FLOPS CHARACTERISTICS TABLES & EXCITATION TABLES SR JK

  10. SUMMARY FLIP FLOPS CHARACTERISTICS TABLES & EXCITATION TABLES D T

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