Null operator in vhdl

Proper usage of operators can make a rather complex task shorter. Basic arithmetic operators are used in almost every program, we will constantly come across examples, and they are easy to use with very low to no syntax restrictions.

Advanced arithmetic operators are not as frequently used but are equally important and powerful if used correctly. Again it is easy to use with a few syntax restrictions. Special arithmetic operators perform nearly identical operations to simple arithmetic operators, the only difference being they are used under special conditions, with a specific syntax. A '-' sign is used to specify the subtraction between two numeric values. These operators are extremely important for advanced mathematics in VHDL.

Let us have a look at the syntax for these operators. An 'abs' is used to specify the absolute value. A 'mod' is used to specify the modulo operator. An 'rem' is used to specify the remainder operator.

A 'not' is used to specify the complement operator. When this operator is used, the numeric value returns unchanged. When this operator is used, the numeric value returns with the negated sign.

Remember to use this operator with parenthesis in the case of any other operator preceding it. Shift operators are used to shift an element of an array of numbers or alphabets left or right by a desired number of steps. Further elaboration with each operator is provided below. Shift operators include:. The sll is the left logical shifter and srl is the right logical shifter. The result of these operations is also a logical array. The sla is the left arithmetic shifter and sra is the right arithmetic shifter.

The rol is the left rotator and ror is the right rotator. In the concatenation, the following situations can take place:. When both operands are one-dimensional arrays of the same type, the concatenation connects the two arrays into one. The new array contains the elements from both arrays. The direction of the new array is the same as the direction in the array of the left operand, but if the left operand is the null array then it is the same as the direction of the right operand.

In case when both operands are null arrays, the direction of the right operand is assumed Example 6. When one of the operands is a one-dimensional array and the second operand is a scalar of the same type as the elements of that array, then the result of the concatenation is the same as in the first point. However, in this case the second operand is treated as a one-dimensional array which contains only one element Example 6.

In case when both operands are of the same scalar type, then the result of concatenation is one-dimensional array with elements of the same types as the operands Example 6. Sign operators are unary operators, i.

The result of the expression evaluation is of the same type as the operand. There are two sign operators Table When these operators are used then sign operator and its operand should be enclosed in parentheses Example 7.

The multiplication and division operators are predefined for all integers, floating point numbers. Under certain conditions, they may be used for operations on physical type objects as well. The mod and rem operators, on the other hand, are defined only for the integers.

When mod and rem operators are used, then both the operands and the result are of the same integer type. The multiplying operators are shown in the Table The abs operator has only one operand. It allows defining the operand's absolute value. The result is of the same type as the operand. The exponentiation operator has two operands. This operator is defined for any integer or floating point number. The right operand exponent must be of integer type.

When the exponent is the positive integer, then the left operand is repeatedly multiplied by itself. When the exponent is the negative number, then the result is a reverse of exponentiation with the exponent equal to the absolute value of the right operand Example 9.

If the exponent is equal to 0 the result will be 1. The null statement The standard requires a choice for every value of the case expression Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually. Related Hot Network Questions. Question feed.