Data types in verilog
anindranallapati
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Dec 11, 2014
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data types in verilog
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DATA TYPES
ANINDRA
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ANINDRA
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TYPES OF DATA TYPES….
There are two groups of data types …..
I.Nets .
II.Variable .
Verilog data types supports 4-state variables 0,1,X,Z.
These net data types are driven in the continuous assignment only .
Synthesizable.
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There are two groups of data types …..
I.Nets .
II.Variable .
Verilog data types supports 4-state variables 0,1,X,Z.
These net data types are driven in the continuous assignment only .
Synthesizable.
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NET DATA TYPE …..
What is net..?
The group of data types which are used for connections are known as net data types .
Net is the group of data types.
The default value of net data types is Z.
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What is net..?
The group of data types which are used for connections are known as net data types .
Net is the group of data types.
The default value of net data types is Z.
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NET DATA TYPES…
There are many data types in the net.
They are as follows :-
wire , tri , tri1, supply0 , wand , triand , tri0 , supply1 , wor , trior , trireg.
In these data types mostly we prefer wire data type .
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There are many data types in the net.
They are as follows :-
wire , tri , tri1, supply0 , wand , triand , tri0 , supply1 , wor , trior , trireg.
In these data types mostly we prefer wire data type .
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NET DATA TYPES…
WIRE :-
A wire net is typically used for nets that are driven by a single gate or continuous
assignment.
Example : wire w1, w2; // declares 2 wires.
The default data type in declaration is wire .
TRI :-
A wire net is typically used for nets that are driven by multiple drivers drive a net .
Logical conflicts from multiple sources on a wire or a tri net result in unknown values
unless the net is controlled by logic strength.
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WIRE :-
A wire net is typically used for nets that are driven by a single gate or continuous
assignment.
Example : wire w1, w2; // declares 2 wires.
The default data type in declaration is wire .
TRI :-
A wire net is typically used for nets that are driven by multiple drivers drive a net .
Logical conflicts from multiple sources on a wire or a tri net result in unknown values
unless the net is controlled by logic strength.
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NET DATA TYPES…
Example : tri [15:0] busa; // a tri-state 16-bit bus .
WIRED NETS :-
Wired nets are of type wor , wand , trior , and triand .
These are used to model wired logic configurations .
These will resolve the conflicts that result when multiple drivers drive the same net.
The wor and trior nets create wired or configurations, such that when any of the drivers is
1, the net is 1.
The wand and triand nets create wired and configurations, such that if any driver is 0, the
net is 0.
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Example : tri [15:0] busa; // a tri-state 16-bit bus .
WIRED NETS :-
Wired nets are of type wor , wand , trior , and triand .
These are used to model wired logic configurations .
These will resolve the conflicts that result when multiple drivers drive the same net.
The wor and trior nets create wired or configurations, such that when any of the drivers is
1, the net is 1.
The wand and triand nets create wired and configurations, such that if any driver is 0, the
net is 0.
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NET DATA TYPES…
EXAMPLES : wor w1 ,w2 ; // or operation .
Wand x,y ; // and operation .
Trior [2:0] bus ; //or operation.
Triand [3:0] bus ; // and operation.
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EXAMPLES : wor w1 ,w2 ; // or operation .
Wand x,y ; // and operation .
Trior [2:0] bus ; //or operation.
Triand [3:0] bus ; // and operation.
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NET DATA TYPES…
TRIREG :-
The trireg net stores a value and is used to model charge storage nodes. A trireg can be one
of two states:
The Driven State :- When at least one driver of a trireg has a value of 1, 0, or x, that value
propagates into the trireg and is the trireg’s driven value.
Capacitive State :- When all the drivers of a trireg net are at the high impedance value (z),
the trireg net retains its last driven value; the high impedance
value does not propagate from the driver to the trireg.
This is only data type in net which is used to store.
EXAMPLE : trireg [2:0] bus ; // a charge storage node .
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TRIREG :-
The trireg net stores a value and is used to model charge storage nodes. A trireg can be one
of two states:
The Driven State :- When at least one driver of a trireg has a value of 1, 0, or x, that value
propagates into the trireg and is the trireg’s driven value.
Capacitive State :- When all the drivers of a trireg net are at the high impedance value (z),
the trireg net retains its last driven value; the high impedance
value does not propagate from the driver to the trireg.
This is only data type in net which is used to store.
EXAMPLE : trireg [2:0] bus ; // a charge storage node .
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NET DATA TYPES …
TRI0 AND TRI1 :-
The tri0 and tri1 nets model nets with resistive pulldown and resistive pullup devices on them.
When no driver drives a tri0 net, its value is 0.
When no driver drives a tri1 net, its value is 1.
These data types are use in the switch level modeling .
SUPPLY0 AND SUPPLY1 :-
These data types are used to strength the data types .
If one or more drivers drives the input the there is a chance of getting unknown value for
output. In order to avoid that we these strengthen levels.
Where supply0(gnd) and 1(vdd) are part of the strength levels.
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TRI0 AND TRI1 :-
The tri0 and tri1 nets model nets with resistive pulldown and resistive pullup devices on them.
When no driver drives a tri0 net, its value is 0.
When no driver drives a tri1 net, its value is 1.
These data types are use in the switch level modeling .
SUPPLY0 AND SUPPLY1 :-
These data types are used to strength the data types .
If one or more drivers drives the input the there is a chance of getting unknown value for
output. In order to avoid that we these strengthen levels.
Where supply0(gnd) and 1(vdd) are part of the strength levels.
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VARIABLE DATA TYPES …
It is used to represent the data storage element.
The default value of variable data type is X.
Data types under the variable data type…
Reg , integer , real , time .
REG :-
This data type is used to represent the data storage element .
It holds the value , Until the a new value is assigned to it .
This reg is used when the variables are declared in the procedural blocks only (always and
initial block).
Example :- reg [2:0] out ; //where the out is used in the procedural block .
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It is used to represent the data storage element.
The default value of variable data type is X.
Data types under the variable data type…
Reg , integer , real , time .
REG :-
This data type is used to represent the data storage element .
It holds the value , Until the a new value is assigned to it .
This reg is used when the variables are declared in the procedural blocks only (always and
initial block).
Example :- reg [2:0] out ; //where the out is used in the procedural block .
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VARIABLE DATA TYPES…
Integer :-
It is used to declare integers.
Example :- integer count ; //assume that count is an integer value.
It is signed.
It is synthesizable .
Default size is 32 bit.
Real :-
Used to declare the real values.
Default size is 64 bit.
Not synthesizable .
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Integer :-
It is used to declare integers.
Example :- integer count ; //assume that count is an integer value.
It is signed.
It is synthesizable .
Default size is 32 bit.
Real :-
Used to declare the real values.
Default size is 64 bit.
Not synthesizable .
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VARIABLE DATA TYPES …
EXAMPLE :- real x;
initial
begin
x=4.47;
#10 x=3.2;
end
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EXAMPLE :- real x;
initial
begin
x=4.47;
#10 x=3.2;
end
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VARIABLE DATA TYPES…
Time :-
This is used to record the simulation time .
Default size is 64 bit .
Not synthesizable .
Example :- time snapshot ;
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Time :-
This is used to record the simulation time .
Default size is 64 bit .
Not synthesizable .
Example :- time snapshot ;
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IMPORTANT POINTS …
Net is not a keyword.
Reg is same not as hardware register .
The default data type is wire.
The rules for using nets and registers in ports of modules and primitives:
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Data type input output inout
wire yes yes yes
Reg No Yes no
Net is not a keyword.
Reg is same not as hardware register .
The default data type is wire.
The rules for using nets and registers in ports of modules and primitives:
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Data type input output inout
wire yes yes yes
Reg No Yes no
THANK YOU…..
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