System Verilog - General Improvements To Classical Verilog

General Improvements To Classical Verilog

In addition to the new features above, SystemVerilog enhances the usability of Verilog's existing language features. The following are some of these enhancements:

  • The procedural assignment operator(s) (<=, =) can now operate directly on arrays.
  • Port (inout, input, output) definitions are now expanded to support a wider variety of datatypes: struct, enum, real, and multi-dimensional types are supported.
  • The for-loop construct now allows automatic variable declaration inside the for statement. And loop-control is improved by the continue and break statements.
  • SystemVerilog adds a do/while to the while construct.
  • Constant variables, i.e. those designated as non-changing during runtime, can be designated by use of const.
  • Variable initialization can now operate on arrays.
  • The preprocessor has improved `define macro-substitution capabilities, specifically substitution within literal-strings (""), as well as concatenation of multiple macro-tokens into a single word.
  • The fork/join construct has been expanded with join_none and join_any.
  • Additions to the `timescale directive allow simulation timescale to be controlled more predictably in a large simulation environment, with each source-file using a local timescale.
  • Task ports can now be declared ref. A reference gives the task body direct access to the source arguments. in the caller's scope. Since it is operating on the original variable itself, rather than a copy of the argument's value, the task/function can modify variables (but not nets) in the caller's scope in realtime. The inout/output port-declarations pass variables by value, and defer updating the caller-scope variable until the moment the task exits.
  • Functions can now be declared void, which means it returns no value.
  • Parameters can be declared any type, including user-defined typedefs.

Besides this, SystemVerilog allows convenient interface to foreign languages (like C/C++), by SystemVerilog DPI (Direct Programming Interface).

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