ControlComponents0 - Control Components Introduction Weve...

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Control Components Introduction We’ve looked at fundamental building blocks That comprise the datapath in embedded design Now want to look at control aspects Control component typically expressed as Finite state machine Collection of such machines Such devices form basis for control Most modern computing and control systems Fundamental Mealy and Moore models Adequate for Introducing FSM concepts Expressing and implementing small designs Expressive power limited for larger systems Combinational explosion When trying to develop input equations Quickly limits utility Will first do quick review of basic concepts Then explore how we can put them to work Implementation of FSM may be in hardware or software Hardware implementation of such machines LSI Arrayed logic PLD ROM Discrete logic Earlier in our studies We’ve looked at the basic storage element Some simple counting and dividing circuits Simple state machines Like counter, divider, timer Have No inputs other than clock Only primitive outputs Such machines referred to as autonomous clock - 1 of 17 -
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We have classed such basic machines as part of datapath In some applications can also be considered as part of control As we move to more complex designs Introduce Inputs Outputs offering rich functionality Such functionality based upon State of the machine Inputs to the machine Finite State Machine Outputs Inputs Our high level block diagram begins with following Now we have Set of inputs Set of outputs Important to recognize Outputs may be State variables Combinations of state variables Combinations of State variables Inputs Let’s increase the level of detail of out state machine We’ll reflect the Inputs State variables Inputs Outputs Finite State Machine State Variables Outputs We see that our state variables Fed back as inputs to our system We’re now looking at the essence of the strength of the machine It has the ability to Recognize the state that it is in Based upon the values of the state variables React based upon that information Decision as to which state to go to next now based upon The current input The state that the machine is currently in Let’s continue increasing the level of detail We’ll increase our view to now include Storage elements comprising the machine Combinational logic - 2 of 17 -
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