By: Travis Hoover2/22/2011CS 147Dr. LeeJK flip-flops

What is a JK Flip-flop?A flip-flop is a circuit that has two stable states and can be used to store state information.

The flip-flop can be made to change state by signals applied to one or more control inputs and will have one or two outputs.

JK Terminology/StructureHas 5 inputs named: J(set),K(reset), PR, CLR, and CLKHas 2 outputs: Q and QSet: when it stores a binary 1Cleared (reset): when it stores a binary 0PR = PresetCLR = ClearCLK = Clock

OutputsThe Q output is the primary output. This means that the binary bit stored in the flip-flop, 1 or 0, is the same as Q.The Q output is the opposite binary bit value that is stored in Q.The PR and CLR inputs always override the J,K inputs.

Inputs: PR and CLRA low at the PR input sets Q = 1A low at the CLR input sets Q = 0

Inputs: J and KThe logic states applied to the J and K inputs cause the flip-flop to operate 4 different ways.

The way the logic state is applied to J and K is called Mode of Operation.

The mode of operation refers to the condition of the flip-flop as it prepares for the positive clock pulse.

Four Modes Of OperationThe 4 modes of operation are: hold, set, reset, toggleJK contains an internal Active Low SR latch.

JKQQMode00QQHold1010Sets0101Resets11QQToggle

Active Low SR LatchPoint to remember:

A 0 at the set or the reset will either set or reset the value of Q.

S setR resetQQ00InvalidInvalid0110100111QQ

Review: Truth Table for NAND2 Inputs:3 Inputs:

ABX001011101110

ABCX00010011010101111001101111011110

Mode of Operation: HoldHold: no change in Q.

JKQQOrig. QOrig. Q000101

Mode of Operation: SetSet: Q = 1.

JKQQOrig. QOrig. Q101001

Mode of Operation: ResetReset: Q = 0.

JKQQOrig. QOrig. Q010110

Mode of Operation: ToggleToggle: Q = Q.

JKQQOrig. QOrig. Q111001

Mode of Operation: Toggle againToggle: Q = Q.

JKQQOrig. QOrig. Q110110

Overview: During a time period

Characteristic EquationCharacteristic Equation:

Q(t+1) = J.Q+ K.Q

QJKQ(t + 1)00000010010101111001101011011110

If only one slide to rememberCharacteristic Equation:

Q(t+1) = J.Q+ K.QQ is the primary output.SR Latch:

A 0 at the set or the reset will either set or reset the value of Q.

JKQQMode00QQHold1010Sets0101Resets11QQToggle

More information / Questions?http://www.wisc-online.com/objects/ViewObject.aspx?ID=DIG3303

http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/jkflipflop.html

http://computer.howstuffworks.com/boolean5.htm

http://www.youtube.com/watch?v=bN02shtPWuI

*Invalid because 0 0 gives matching outputs for both Q and Q*