FSM state register?

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cafukarfoo

Joined: 25 Jul 2007
Posts: 164
Helped: 3

01 Aug 2007 14:21 fsm coding with one hot decoding

What does it mean for the statement below:

"FSM state register should always be one-hot"

Thanks in advance for your help

RBB

Joined: 02 Jul 2007
Posts: 115
Helped: 11
Location: USA

01 Aug 2007 15:43 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

cafukarfoo

Joined: 25 Jul 2007
Posts: 164
Helped: 3

02 Aug 2007 2:58 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?

sam536

Joined: 04 Jul 2007
Posts: 137
Helped: 14
Location: Tokyo

02 Aug 2007 3:36 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

cafukarfoo

Joined: 25 Jul 2007
Posts: 164
Helped: 3

02 Aug 2007 7:37 Re: FSM state register?

cool sam

your reply is really helpful.

vamsi_addagada

Joined: 05 Jul 2007
Posts: 132
Helped: 3
Location: bangalore

02 Aug 2007 9:17 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