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1st August 2007, 14:21 #1
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What does it mean that FSM state register is onehot?
What does it mean for the statement below:
"FSM state register should always be onehot"
Thanks in advance for your help

1st August 2007, 15:43 #2
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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
Onehot state machines can be bigger than normal binary encoded state machines, but the next state decode is usually smaller in a onehot state machine.
Also notice a onehot state machine is hamming encoded, so that two bits must change for a valid state transition
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1st August 2007, 15:43

2nd August 2007, 02:58 #3
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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 onehot?

2nd August 2007, 02:58

2nd August 2007, 03:36 #4
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Re: FSM state register?
Onehot 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 onehot encoding is implemented with one FF. There are lot of unused states in the Onehot 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 Onehot, are Adjucent encoding, Random encoding, UserSpecific encoding, Moore encoding, Binary encoding and etc..
Regards,
Sam
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2nd August 2007, 03:36

2nd August 2007, 07:37 #5
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Re: FSM state register?
cool sam
your reply is really helpful.

2nd August 2007, 09:17 #6
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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

2nd August 2007, 09:17

23rd August 2007, 17:49 #7
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Re: FSM state register?
The only advantage of using onehot Fsm is the elimination of decoder...

24th August 2007, 09:08 #8
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FSM state register?
fsm state coding depends on your choice, onehot use more register but give u high speed.

13th January 2008, 04:15 #9
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Re: FSM state register?
Can One  Hot encoding makes data path short.
If yes how?

13th January 2008, 06:07 #10
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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 onehot is a best choice
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