l10mjor_minorfsm

l10mjor_minorfsm - L10: Major/Minor FSMs, , Lab 3, and...

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L10: Major/Minor L10: Major/Minor FSMs FSMs , , Lab 3, and RAM/ROM Instantiation Lab 3, and RAM/ROM Instantiation Courtesy of Rex Min . Used with permission. L10: 6.111 Spring 2004 Introductory Digital Systems Laboratory 1
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Toward FSM Modularity Toward FSM Modularity ± Consider the following abstract FSM: S 0 a 1 b 1 c 1 d 1 S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9 a 2 b 2 c 2 d 2 a 3 b 3 c 3 d 3 ± Suppose that each set of states a x ...d x is a “sub-FSM” that produces exactly the same outputs. ± Can we simplify the FSM by removing equivalent states? No! The outputs may be the same, but the next-state transitions are not. ± This situation closely resembles a procedure call or function call in software. ..how can we apply this concept to FSMs? L10: 6.111 Spring 2004 Introductory Digital Systems Laboratory 2
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The Major/Minor FSM Abstraction The Major/Minor FSM Abstraction Major FSM Minor FSM A Minor FSM B START A START B BUSY A BUSY B CLK RESET RESET CLK ± Subtasks are encapsulated in minor FSMs with common reset and clock ± Simple communication abstraction: ² START: tells the minor FSM to begin operation (the call) ² BUSY: tells the major FSM whether the minor is done (the return) ± The major/minor abstraction is great for. .. ² Modular designs ( always a good thing) ² Tasks that occur often but in different contexts ² Tasks that require a variable/unknown period of time ² Event-driven systems L10: 6.111 Spring 2004 Introductory Digital Systems Laboratory 3
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Inside the Major FSM Inside the Major FSM S 1 S 2 START S 3 S 4 ... BUSY BUSY BUSY BUSY BUSY BUSY 1. Wait until the minor FSM is ready 2. Trigger the minor FSM (and make sure it’s started) 3. Wait until the minor FSM is done START BUSY Major FSM State S 1 S 2 S 2 S 3 S 3 S 3 S 4 CLK L10: 6.111 Spring 2004 Introductory Digital Systems Laboratory 4
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Inside the Minor FSM T 2 BUSY T 3 BUSY T 4 BUSY 1. Wait for a trigger from the major FSM 2. Do some useful work T 1 BUSY START START START BUSY Major FSM State S 1 S 2 S 2 S 3 S 3 S 3 S 4 CLK Minor FSM State T 1 T 1 T 2 T 3 T 4 T 1 T 1 3. Signal to the
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This note was uploaded on 07/21/2009 for the course EECS 6.111 taught by Professor Prof.ananthachandrakasan during the Spring '04 term at MIT.

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l10mjor_minorfsm - L10: Major/Minor FSMs, , Lab 3, and...

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