Subversion Repositories srdydrdy_lib

//----------------------------------------------------------------------
// Srdy/Drdy output block
//
// Halts timing on all signals except ic_drdy
// ic_drdy is a combinatorial path from p_drdy
//
// Naming convention: c = consumer, p = producer, i = internal interface
//----------------------------------------------------------------------
// Author: Guy Hutchison
//
// This block is uncopyrighted and released into the public domain.
//----------------------------------------------------------------------
 
// Clocking statement for synchronous blocks.  Default is for
// posedge clocking and positive async reset
`ifndef SDLIB_CLOCKING 
 `define SDLIB_CLOCKING posedge clk or posedge reset
`endif
 
// delay unit for nonblocking assigns, default is to #1
`ifndef SDLIB_DELAY 
 `define SDLIB_DELAY #1 
`endif
 
module sd_output
  #(parameter width = 8)
  (
   input              clk,
   input              reset,
   input              ic_srdy,
   output reg         ic_drdy,
   input [width-1:0]  ic_data,
 
   output reg         p_srdy,
   input              p_drdy,
   output reg [width-1:0] p_data
   );
 
  reg 	  load;   // true when data will be loaded into p_data
  reg 	  drain;  // true when data will be emptied from p_data
  reg 	  hold;   // true when data will be held in p_data
  reg 	  nxt_p_srdy;
 
  always @*
    begin
      drain = p_srdy & p_drdy;
      hold  = p_srdy & !p_drdy;
      ic_drdy = drain | !p_srdy;
      load  = ic_srdy & ic_drdy;
      nxt_p_srdy = load | hold;
    end
 
  always @(`SDLIB_CLOCKING)
    begin
      if (reset)
	begin
	  p_srdy <= `SDLIB_DELAY 0;
	end
      else
	begin
	  p_srdy <= `SDLIB_DELAY nxt_p_srdy;
	end // else: !if(reset)
    end // always @ (posedge clk)
 
  always @(posedge clk)
    if (load)
      p_data <= `SDLIB_DELAY ic_data;
 
endmodule // it_output