design/sys/iop/niu/rtl/niu_pio_accepted_sm.v

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/*************************************************************************
 *
 * File Name    : niu_pio_accepted_sm.v
 * Author Name  : John Lo
 * Description  : It contains niu pio interface, interrupt controller,
 *                UCB for N2.
 * Parent Module: niu
 * Child  Module:
 * Interface Mod: many.
 * Date Created : 3/08/2004
 *
 * Copyright (c) 2020, Sun Microsystems, Inc.
 * Sun Proprietary and Confidential
 *
 * Modification :
 *
 * Synthesis Notes:
 *
 *************************************************************************/

module niu_pio_accepted_sm (/*AUTOARG*/
   // Outputs
   accepted, accepted_state,
   // Inputs
   clk, reset, full, ucb_rd_req, ucb_wr_req
   );

   input                      clk;
   input                      reset;
   input                      full;
   input                      ucb_rd_req;
   input                      ucb_wr_req;

   output                     accepted;
   output [1:0]               accepted_state;

   reg  [1:0]                 nx_accepted_state;
   reg                        accepted;

   parameter                  IDLE   = 2'd0;
   parameter                  ACCEPT = 2'd1;
   parameter                  DLY1   = 2'd2;
   parameter                  DLY2   = 2'd3;

// combination logic
always @ (/*AUTOSENSE*/accepted_state or full or ucb_rd_req
          or ucb_wr_req)
  begin
                  nx_accepted_state = IDLE;
                  accepted          = 0;
     case (accepted_state) // synopsys full_case parallel_case
       IDLE:   begin
                 if ((~full) & (ucb_rd_req | ucb_wr_req))
                      nx_accepted_state = ACCEPT;
                 else nx_accepted_state = accepted_state; // stay
               end

       ACCEPT: begin
                  nx_accepted_state = DLY1;
                  accepted          = 1;

               end
       DLY1:      nx_accepted_state = DLY2;

       DLY2:      nx_accepted_state = IDLE;

       default:begin
                  nx_accepted_state = IDLE;
                  accepted          = 0;
               end
     endcase
  end

// seq part
dffr #(2) accepted_state_dffr(.d(nx_accepted_state[1:0]),.reset(reset),.clk(clk),.q(accepted_state[1:0]));


endmodule // niu_pio_accepted_sm