Variables in Behavioral Verilog - 2024.1 English

Vivado Design Suite User Guide: Synthesis (UG901)

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2024.1 English
  • Variables in behavioral Verilog are declared as an integer.
  • These declarations are used in test code only. Verilog provides data types such as reg and wire for actual hardware description.
  • The difference between reg and wire depends on whether the variable is given its value in a procedural block (reg) or in a continuous assignment (wire).
    • Both reg and wire have a default width of one bit (scalar).
    • To specify an N-bit width (vectors) for a declared reg or wire, the left and right bit positions are defined in square brackets separated by a colon.
    • In Verilog-2001, reg and wire data types can be signed or unsigned.