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Lecture 3 – Common Elements

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Common Logic Elements

• Review Lecture 2 sequential elements• Examine the data sheet for some of these

elements• When using element in a design you start with

the documentation for the element

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Common Sequential Elements

• Basic Element– The Latch – A latch is a level sensitive component

that stores and holds a value– What does level sensitive mean?

• Flip Flops are edge triggered elements– F/F can be constructed of a Master Slave arrangement of 2

latches– Master is level sensitive to new input– On edge master is locked and its value is transmitted to

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Another Basic Elements

• Register– Registers are composed of latches or F/Fs– Several uses• Register sets – driven from/drive busses• Input register for functional units• Output hold register for a functional unit• Configuration register

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Edge Triggered F/F

• Edge triggered flip-flops can be– Master Slave – formed from 2 latches

– Discrete design

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Sequential ComponentsMultiple ICs

• Cascaded Elements (Registers, Counters)• State Machines (FSM)• Controllers• Cooperating State Machines

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Data Books

• Data Books List Components and their parameters

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More Data Book Components

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D F/F Data Sheet

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The inputs and outputs specs

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The circuit Implementation

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Various type of implmentation

• Note this is• A Master-Slave• Implementation

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Timing

• And has its own• Implementation• And timing

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Voltage and Current Specs

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Higher level components

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Use of data

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Use of data

• You use the data to analyze circuit and then can answer questions on it as illustrated in the following

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Some Specifications

Clock Period

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Solution

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What are the states

• Develop the state table• Pick a state to start with

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Self Starting Circuits

• Circuits that end up in a valid state regardless of the state the FSM starts in.

• Is this circuit self starting?

• Go to www.wikipedia.com and look at material there on Finite State Machine