rotate 100

Build a 100-bit left/right rotator, with synchronous load and left/right enable. A rotator shifts-in the shifted-out bit from the other end of the register, unlike a shifter that discards the shifted-out bit and shifts in a zero. If enabled, a rotator rotates the bits around and does not modify/discard them.

• load: Loads shift register with data[99:0] instead of rotating.
• ena[1:0]: Chooses whether and which direction to rotate.
  • 2'b01 rotates right by one bit
  • 2'b10 rotates left by one bit
  • 2'b00 and 2'b11 do not rotate.
• q: The contents of the rotator.

Program:

module top_module(
    input clk,
    input load,
    input [1:0] ena,
    input [99:0] data,
    output reg [99:0] q); 
    always@(posedge clk )begin        // don't need "negedge ena" in the list because i                                                                                //synchronous
        if(load)
            q<=data[99:0];
        else begin
            case(ena)                                 //choose mode to run
                2'b00:;                                 //2'b00 and 2'b11 do not rotate.
                2'b01:q<={q[0],q[99:1]};        //2'b01 rotates right by one bit
                2'b10:q<={q[98:0],q[99]};      //2'b10 rotates left by one bit
                2'b11:;                                  //2'b00 and 2'b11 do not rotate.
            endcase
            end
    end

endmodule