Verilog Studies

Repository contents

• Data Types and Operators: code examples.
• Numbering Systems: adders.

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Arithmetic Operators:

• **: Exponentiation
• *: Product
• /: Division
• %: Modulus or Remainder
• +: Sum
• -: Difference

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Relational Operators:

• >: Greater than
• >=: Greater than or equal
• <: Less than
• <=: Less than or equal

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Bitwise Operators:

• AND Operator &: Returns 1 if both operands are 1.
• OR Operator |: Returns 1 if at least one of the operands is 1.
• NOT Operator ~: Inverts the logical value of the operand (if it’s 0, it becomes 1, and vice versa).
• XOR Operator ^: Returns 1 if the operands are different (if one is 1 and the other is 0).

This type of signal manipulation is common in digital circuits, where logical operations are used to control data flow and conditions.

Logical Operators:

• !: Logical NOT (inverts the bits).
• &&: Logical AND (returns 1 if both bits are 1).
• ||: Logical OR (returns 1 if at least one bit is 1).

Summary:

• Use & when you need to compare bit by bit between two values.
• Use && when you need to evaluate a logical condition between two values, returning 1 (true) or 0 (false).

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Equality Operators:

Logical Equality (for design):

• ==: Equal
• !=: Not equal

Case Equality (for testbench):

• ===: Case equality
• !==: Case inequality

If logical equality operators get variables with Z (high impedance) or X (unknown) values, then the result can be unknown.

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Concatenation Operator:

• {}: Concatenation

Join bits from different vectors to form a new vector.

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Replication Operator:

• {{}}: Replication

Concatenation performed for a fixed number of times.

Syntax: {<number_times>{<some_binary_value>}}

Example: a[5:0] = {3{b[1:0]}} means a[5:0] = {b[1:0], b[1:0], b[1:0]}

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Operator Precedence

1. Unary (highest)

• Unary operators have the highest precedence.
• Examples:
  • +: Unary plus (positive sign)
  • -: Unary minus (negation)
  • !: Logical NOT (inverts the bits)
  • ~: Bitwise NOT (inverts the bits)

2. Exponentiation

• Exponentiation (if supported) is evaluated next.
• Example: ** (Exponentiation)

3. Arithmetic Operators

• Arithmetic operations like multiplication, division, and modulus come after exponentiation.
• Examples:
  • *: Multiplication
  • /: Division
  • %: Modulus (remainder)

4. Shift Operators

• Shift operators are evaluated after arithmetic operations.
• Examples:
  • <<: Logical left shift
  • >>: Logical right shift

5. Relational Operators

• Relational operators are used for comparison and come after arithmetic and shift operations.
• Examples:
  • >: Greater than
  • >=: Greater than or equal
  • <: Less than
  • <=: Less than or equal

6. Equality Operators

• Equality operators check if values are equal or not, and are evaluated after relational operators.
• Examples:
  • ==: Equal
  • !=: Not equal

7. Bitwise Operators

• Bitwise operators perform bit-level operations and are evaluated after equality operators.
• Examples:
  • &: Bitwise AND
  • ^: Bitwise XOR
  • |: Bitwise OR

8. Logical Operators

• Logical operators are evaluated after bitwise operations.
• Examples:
  • &&: Logical AND
  • ||: Logical OR

9. Conditional Operators

• Conditional operators are evaluated after logical operators.
• Example:
  • ? :: Ternary conditional (if-else)

10. Concatenation (lowest)

• Concatenation has the lowest precedence in Verilog.
• Example:
  • {}: Concatenation operator (combines multiple bits or signals)