VHDL

Using Arithmetic & Relational Operators

The std_logic_arith package in the ieee library includes a number of arithmetic and relational operators for use with SIGNED and UNSIGNED types. These operators are shown below:

Type: Operator: Examples: Description:
Arithmetic + 
- 
* 		 a + b, +a 
a - b, -a 
a * b 		 addition 
subtraction 
multiplication 
Relational < 
<= 
> 
>= 
= 
/= 
 a < b 
a <= b 
a > b 
a >= b 
a = b 
a /= b 		 less than 
less than or equal to 
greater than 
greater than or equal to 
equal to 
not equal to 

NOTE Operands in arithmetic and relational operations cannot have a greater width than the result. In arithmetic operations, one of the operands must have the same width as the result; the other is sign- or zero-extended. In relational operations, the result has a single bit.


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