Verilog case

In Verilog, the "case" statement is used for conditional branching. It allows the programmer to specify multiple conditions and corresponding actions to be taken based on the evaluation of these conditions. The syntax of the "case" statement is as follows:

case (expression)
  value1: action1;
  value2: action2;
  ...
  default: default_action;
endcase

Here, "expression" is the variable or expression to be evaluated, and "value1", "value2", etc. are the possible values that the expression can take. For each value, there is a corresponding action to be taken, specified by "action1", "action2", etc. The "default" keyword is used to specify the action to be taken when none of the other values match the expression.

For example, the following Verilog code uses a "case" statement to implement a simple multiplexer:

module mux(input sel, input in0, input in1, output reg out);

  always @ (sel, in0, in1)
    case (sel)
      1'b0: out = in0;
      1'b1: out = in1;
      default: out = 1'b0; // default action
    endcase

endmodule

Here, the "sel" input determines which input to pass through to the output "out". If "sel" is 0, then "in0" is passed through, and if "sel" is 1, then "in1" is passed through. The "default" action sets "out" to 0 if none of the other cases match.