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    What does it mean that FSM state register is one-hot?

    What does it mean for the statement below:

    "FSM state register should always be one-hot"

    Thanks in advance for your help

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    FSM state register?

    One hot state machines have only a one signal in the state register is a '1'.

    For example
    State A: 0001
    State B: 0010
    State C: 0100
    State D: 1000

    One-hot state machines can be bigger than normal binary encoded state machines, but the next state decode is usually smaller in a one-hot state machine.

    Also notice a one-hot state machine is hamming encoded, so that two bits must change for a valid state transition


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    •   Alt1st August 2007, 15:43

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    Re: FSM state register?

    Thanks for your reply RBB.

    Let say i have state machine below

    State A ( 0 ) : 0000
    State B ( 5 ) : 0101
    State C ( 10 ) : 1010

    Above is my FSM. But i have more than 1 signal have logic 1.

    So how can the FSM state register should always be one-hot?



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    Re: FSM state register?

    One-hot encoding sets one bit in the state register for each state. For ex, FSM with 16 states required 16 FF`s for one hot encoding.


    Each node of the state diagram in one-hot encoding is implemented with one FF. There are lot of unused states in the One-hot encoding. If you use N FF , there will be 2 power N used states , 2 power N - N states are unused states.

    In your example, to represent 5 , you need to specify 10000 not 0101...and etc..


    There are diffrent FSM encoding style including One-hot, are Adjucent encoding, Random encoding, User-Specific encoding, Moore encoding, Binary encoding and etc..


    Regards,
    Sam


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    •   Alt2nd August 2007, 03:36

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    Re: FSM state register?

    cool sam

    your reply is really helpful.



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    FSM state register?

    hi
    FSM is the finite state machine is used for control logics.
    one hot machine is each state taken one FF ex:-0001
    it is reduecd glitch
    binary state machine is the taken FF s depend on the state 2N= state ,N is the no .of FF
    it is used for reduecd area.

    vamsi

    Added after 35 seconds:

    hi
    FSM is the finite state machine is used for control logics.
    one hot machine is each state taken one FF ex:-0001
    it is reduecd glitch
    binary state machine is the taken FF s depend on the state 2N= state ,N is the no .of FF
    it is used for reduecd area.

    vamsi



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    Re: FSM state register?

    The only advantage of using one-hot Fsm is the elimination of decoder...



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    FSM state register?

    fsm state coding depends on your choice, one-hot use more register but give u high speed.



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    Re: FSM state register?

    Can One - Hot encoding makes data path short.

    If yes how?



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    FSM state register?

    it relies on how many state your FSM has
    when the state number is big and require high speed
    then one-hot is a best choice



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