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one_hot and zero_one_hot

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wangkl

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zero_one_hot

What's the difference between these two concepts: one_hot and zero_one_hot?
I'm a little bit confused.
 

what does one_hot pragma do

Hint:
Use google to find zero_one_hot and read the first record.
 

zero one dirty.com

It's a pdf file and without any explaination.
I guess google is characterized for different location.

Actually, I met problem while I read Cadence LEC document:

ADD PIN CONSTRAINTS

ONE_Hot Specifies that only one of the pins can have a high value.
ONE_Cold Specifies that only one of the pins can have a low value.
ZERO_ONE_Hot All pins can have a low value, but only one can have a high value.
ZERO_ONE_Cold All pins can have a high value, but only one can have a low value.
 

example of one hot constraints in cadence lec

OK.

I will post what's in the pdf:

The definition of one-hot as given here ("in which only one
signal in the collection is active at a given time") is useful one,
but is not the normal definition of one-hot. (In OVL, the Open
Verification Library, this check is known as zero_one_hot.)
This will cause confusion.

Change the definition of ONE_HOT to "...in
which one and only one signal in the collection
is active at a given time", and add a second
attribute ZERO_ONE_HOT with the definition
"...in which at most one signal in the collection
is active at a given time". Similarly for
ONE_COLD and ONES_ONE_COLD.


Will u be satisfied now ? :)
 

    W

    wangkl

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zero one dirty

So in the other word:

One_hot: at least 1, only 1 and at most 1 "one" is active in a given time.

zero_one_hot: at least 0, and at most 1 "one" is active in a given time.

Is my understanding correct? Thanks!
 

can u explain for one cold with one simple example
 

one hot:

only following states is available
state[2:0] = 3'b001;
state[2:0] = 3'b010;
state[2:0] = 3'b100;


zero one hot:

only following states is available
state[2:0] = 3'b001;
state[2:0] = 3'b010;
state[2:0] = 3'b100;
state[2:0] = 3'b000;

one cold:

only following states is available
state[2:0] = ~3'b001;
state[2:0] = ~3'b010;
state[2:0] = ~3'b100;


zero one cold:

only following states is available
state[2:0] = ~3'b001;
state[2:0] = ~3'b010;
state[2:0] = ~3'b100;
state[2:0] = ~3'b000;
 

thanks
but how synthesis tool will understand this condition
whether we have to set any pragma for this conditions?
 

thanks.i usually use one-hot.could you give me the difference when we synthesis one-hot and zero-one-hot?
 

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