List of operators:
Arithmetic:
| + -- * / |
Modulus:
| % |
Relational:
| < <= > >= |
Logical:
| ! && || |
Logical equality:
| == != |
Case equality:
| === !== |
Bit-wise:
| ~ & | ^ ~^ ^~ |
Reduction:
| & ~& | ~| ^ ~^ ^~ |
Shift:
| << >> |
Conditional:
| ? : |
Event or:
| or |
Concatenations:
| {} {{}} |
Priority:
This list provides priority of Verilog Operators:
Operator
|
Type
|
| + - ! ~ |
Unary
|
| * / % |
Arithmetic
|
| + - (binary) |
Binary
|
| << >> |
Shift
|
| < <= > => |
Relational
|
| == != === !== |
Equality
|
| & ~& |
and nand
|
| ^ ~^ ^~ |
xor xnor
|
| | ~| |
or nor
|
| && |
Logical and
|
| || |
Logical or
|
| ?: |
Conditional operator
|
Arithmetic operators
Operator
|
Description
|
| a + b |
(Addition) a plus b
|
| a - b |
(Subtraction) a minus b
|
| a * b |
(Multiplication) a multiplied by b
|
| a / b |
(Division) a divide by b
|
| a % b |
(Modulus) a modulo b
|
module operators(); reg [3:0] a, b; initial begin a = 3; b = 5; $display(a + b ); // 8 $display(a ? b: 1 ); // 5 $display(a * b ); // 15 $display(a / b ); // 0 $display(b / a ); // 1 $display(a % b ); // 3 $display(7 % 3 ); // 1 $display(7 % -3 ); // 1 $display(-7 % 3 ); // -1 $display(-7 % -3 ); // -1 end endmodule |
| Output:8 5 15 0 1 3 1 1 -1 -1 |
Relational operators
Operator
|
Description
|
| a < b |
a less than b
|
| a > b |
a greater than b
|
| a <= b |
a less than or equal to b
|
| a => b |
a greater than or equal to b
|
Equality operators
The equality operators are used to compare expressions. If a comparison fails, then the result will be 0, otherwise it will be 1.
If both operands of logical equality (==) or logical inequality (!=) contain unknown (x) or a high-impedance (z) value, then the result of comparison will be unknown (x). Otherwise it will be 1 or 0.
If operands of case equality (===) or case inequality (!==) contain unknown (x) or a high-impedance (z) value, then the result will be calculated bit by bit.
Logical operators
The logical operators are used to connect expressions.
Operator
|
Description
|
| a && b |
a and b
|
| a || b |
a or b
|
| !a |
not a
|
Bit-wise operators
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
Reduction operators
The reduction operator produces a 1-bit result. This result is calculated by recursively applying bit-wise operation on all bits of the operand. At each step of this recursive calculation the logical bit-wise operation is performed on the result of a previous operation and on the next bit of the operand. The operation is repeated for all bits of the operand.
Shift operators
The shift operators perform left and right shifts on their left operand by the number of positions specified by their right operand. All vacated bits are filled with zeroes. If the expression that specifies the number of bits to shift (right operand) has unknown (x) or high-impedance (z) value, then result will be unknown.
Examples of using the shift operators are in shown Example 7.
Conditional operator
The conditional operator is described in the Conditional operator section.
Concatenations
Concatenations are described in the Concatenations section.
Event or operator
The event or operator is described in the section on Procedural timing controls.
Example:
module example(); reg [3:0] a, b; reg [7:0] c, d; initial begin a = 4'b1110; //14 b = 4'b0110; //5 $display( "%b", a < b );// false - 0 $display( "%b", a > 8 );// true - 1 $display( "%b", a <= b );// false - 0 $display( "%b", a >= 10 );// true - 1 $display( "%b", a < 4'b1zzz );// unknown - x $display( "%b", b < 4'b1x01 );// unknown - x a = 4'b1100; b = 4'b101x; $display( "%b", a == 4'b1100 ); // true - 1 $display( "%b", a != 4'b1100 );// false - 0 $display( "%b", a == 4'b1z10 );// false - 0 $display( "%b", a != 4'b100x );// true ? 1 $display( "%b", b == 4'b101x );// unknown - x $display( "%b", b != 4'b101x );// unknown - x $display( "%b", b === 4'b101x );// true - 1 $display( "%b", b !== 4'b101x );// false - 0 a = 4'b1100; b = 4'b0000; $display( "%b", !a );// 0 - false $display( "%b", !b );// 1 - true $display( "%b", a && b ); // 0 - false $display( "%b", a || b );// 1 ? true c = 8'b1010xzxz; d = 8'b10010011; $display( "%b", c & d ); //= 8'b100000xx; $display( "%b", c | d ); //= 8'b1011xx11; $display( "%b", c ^ d ); //= 8'b0011xxxx; $display( "%b", c ~^ d ); //= 8'b1100xxxx; $display( "%b", ~ c ); //= 8'b0101xxxx; a = 4'b1111; $display( "%b", a << 3 ); //= 4'b1000 $display( "%b", a >> 3 ); //= 4'b0001 $display( "%b", a << 1'bz ); //= 4'bxxxx $display( "%b", a >> 1'bx ); //= 4'bxxxx end endmodule |
value
|
&
|
~&
|
|
|
~|
|
^
|
~^
|
^~
|
4'b0000
|
0
|
1
|
0
|
1
|
0
|
1
|
1
|
4'b0001
|
0
|
1
|
1
|
0
|
1
|
0
|
0
|
4'b0011
|
0
|
1
|
1
|
0
|
0
|
1
|
1
|
4'b0111
|
0
|
1
|
1
|
0
|
1
|
0
|
0
|
4'b1111
|
1
|
0
|
1
|
0
|
0
|
1
|
1
|
4'b01xx
|
0
|
1
|
1
|
0
|
x
|
x
|
x
|
4'b01z0
|
0
|
1
|
1
|
0
|
x
|
x
|
x
|
Reduction operators
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