VERILOG031: “default” should be the last item of a “case” statement

Summary

Reliability	Security	Maintainability	Code attribute	Effort to fix	Tags

-	-	MEDIUM	Intentionality \| Clear	5min	synthesis, readability, vscode, simulation, linter

Description

Related rules

Each case statement should define a "default" case

Move the default clause to the end of the case statement.

Noncompliant code example

unique casez (select)
  default: operand = '0; // Noncompliant: Should be moved to the end
  3'b000: operand = accum0 >> 0;
  3'b001: operand = accum0 >> 1;
  3'b010: operand = accum1 >> 0;
  3'b011: operand = accum1 >> 1;
  3'b1??: operand = regfile[select[1:0]];
endcase

Compliant solution

unique casez (select)
  3'b000: operand = accum0 >> 0;
  3'b001: operand = accum0 >> 1;
  3'b010: operand = accum1 >> 0;
  3'b011: operand = accum1 >> 1;
  3'b1??: operand = regfile[select[1:0]];
  default: operand = '0;
endcase

To improve readability, default should be the last item of a case statement.

Parameters

No parameters.