ITEC 352

Lecture 9Flip Flops

Flip flops

Review

• Questions?• HW #2 posted, due next Friday at

10PM• Floating point numbers

Flip flops

Outline

• Rationale• SR• D• T• JK

Flip flops

Gates

• So far what have we seen circuitry wise?

• What can we do with what we have learned?

• What can’t we do?

Flip flops

Idea

• Have the output tied to the input

Flip flops

Why?

• State–Why is the state of a machine

important?– How does this relate to programming?–What does hooking up the output to the

input do to our idea of timing?

• Not a new idea– Back in 1918

Flip flops

SR

• Set and reset latch– Can be implemented with NAND gates

What is the truth table for this set of gates?What input set should we stay away from?

Flip flops

Gating the gates

• What does this image bring to mind?

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Issue

• Changes in the input immediately change the output

• Sometimes keeping the state the same even though the input changes is required

What is the truth table?What do you think E does

Flip flops

D Latch

• Adding the 1/1 combination– Just like an SR latch except it handles

the 1 1 input condition gracefully

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Clock cycles

• Some sort of order needed– Conductor in an orchestra

• Need to preserve values through each “beat”

• Behavior– Designed to delay the output by 1 cycle– Allows access to previous cycles result

Clock pulse

Flip flops

T Flip/flop

• Toggles value when T is 1• Clock pulse changes values

Flip flops

JK Flip/Flop

• Universal flip/flop• J=set, K=reset• 0 0 is hold• 1 1 is toggle

Flip flops

Next steps

• Have the capability to store information

• Have the capability to manipulate binary bits for mathematical and boolean tasks

• How does it all fit together to form a computer?

Flip flops

Summary

• Flip flops• Latches• Storing bits