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

1. ## 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"

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2. ## 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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3. ## Re: FSM state register?

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?

4. ## 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

1 members found this post helpful.

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cool sam

6. ## 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

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

7. ## Re: FSM state register?

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

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8. ## FSM state register?

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

9. ## Re: FSM state register?

Can One - Hot encoding makes data path short.

If yes how?

10. ## 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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