Subversion Repositories openrisc_2011-10-31

//////////////////////////////////////////////////////////////////////
//
// clkgen
//
// Handles clock and reset generation for rest of design
//
//
//////////////////////////////////////////////////////////////////////
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//// Copyright (C) 2009, 2010 Authors and OPENCORES.ORG           ////
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//// This source file is free software; you can redistribute it   ////
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//////////////////////////////////////////////////////////////////////
//
// A simple implementation for the main generic ORPSoC simulations
//
 
`include "timescale.v"
`include "orpsoc-defines.v"
 
module clkgen
  (
   // Main clocks in, depending on board
   clk_pad_i,
 
   // Input reset - through a buffer, asynchronous
   async_rst_o,
   // Wishbone clock and reset out  
   wb_clk_o,
   wb_rst_o,
 
   // JTAG clock
`ifdef JTAG_DEBUG
   tck_pad_i,
   dbg_tck_o,
`endif      
 
   // Asynchronous, active low reset in
   rst_n_pad_i
 
   );
 
   input clk_pad_i;
 
   output async_rst_o;
 
   output wb_rst_o;
   output wb_clk_o;
 
`ifdef JTAG_DEBUG
   input  tck_pad_i;
   output dbg_tck_o;
`endif      
 
   // Asynchronous, active low reset (pushbutton, typically)
   input  rst_n_pad_i;
 
   // First, deal with the asychronous reset
   wire   async_rst_n;
 
   // An input buffer is usually instantiated here
   assign async_rst_n = rst_n_pad_i;
 
   // Everyone likes active-high reset signals...
   assign async_rst_o = ~async_rst_n;
 
`ifdef JTAG_DEBUG
   assign dbg_tck_o = tck_pad_i;
`endif
 
   //
   // Declare synchronous reset wires here
   //
 
   // An active-low synchronous reset signal (usually a PLL lock signal)
   wire   sync_rst_n;
   assign sync_rst_n  = async_rst_n; // Pretend it's somehow synchronous now
 
 
   // Here we just assign "board" clock (really test) to wishbone clock
   assign wb_clk_o = clk_pad_i;
 
   //
   // Reset generation
   //
   //
 
   // Reset generation for wishbone
   reg [15:0] 	   wb_rst_shr;
   always @(posedge wb_clk_o or posedge async_rst_o)
     if (async_rst_o)
       wb_rst_shr <= 16'hffff;
     else
       wb_rst_shr <= {wb_rst_shr[14:0], ~(sync_rst_n)};
 
   assign wb_rst_o = wb_rst_shr[15];
 
endmodule // clkgen