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//////////////////////////////////////////////////////////////////////

////                                                              ////

////  OMS 8051 cores clockgen Module                              ////

////                                                              ////

////  This file is part of the OMS 8051 cores project             ////

////  http://www.opencores.org/cores/oms8051mini/                 ////

////                                                              ////

////  Description                                                 ////

////  OMS 8051 definitions.                                       ////

////                                                              ////

////  To Do:                                                      ////

////    nothing                                                   ////

////                                                              ////

////  Author(s):                                                  ////

////      - Dinesh Annayya, dinesha@opencores.org                 ////

////                                                              ////

////  Revision : Nov 26, 2016                                     //// 

////                                                              ////

//////////////////////////////////////////////////////////////////////

////                                                              ////

//// Copyright (C) 2000 Authors and OPENCORES.ORG                 ////

////                                                              ////

//// This source file may be used and distributed without         ////

//// restriction provided that this copyright statement is not    ////

//// removed from the file and that any derivative work contains  ////

//// the original copyright notice and the associated disclaimer. ////

////                                                              ////

//// This source file is free software; you can redistribute it   ////

//// and/or modify it under the terms of the GNU Lesser General   ////

//// Public License as published by the Free Software Foundation; ////

//// either version 2.1 of the License, or (at your option) any   ////

//// later version.                                               ////

////                                                              ////

//// This source is distributed in the hope that it will be       ////

//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////

//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////

//// PURPOSE.  See the GNU Lesser General Public License for more ////

//// details.                                                     ////

////                                                              ////

//// You should have received a copy of the GNU Lesser General    ////

//// Public License along with this source; if not, download it   ////

//// from http://www.opencores.org/lgpl.shtml                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

module clkgen (

               reset_n      ,

               fastsim_mode ,

               mastermode   ,

               xtal_clk     ,

               clkout       ,

               gen_resetn   ,

               risc_reset   ,

               app_clk      ,

               uart_ref_clk

              );

input           reset_n        ; // Async reset signal

input         fastsim_mode   ; // fast sim mode = 1

input         mastermode     ; // 1 : Risc master mode

input           xtal_clk       ; // Xtal clock-25Mhx 

output        clkout         ; // clock output, 250Mhz

output        gen_resetn     ; // internally generated reset

output        risc_reset      ; // internally generated reset

output        app_clk        ; // application clock

output        uart_ref_clk   ; // uart 16x Ref clock

wire          hard_reset_st  ;

wire          configure_st   ;

wire          wait_pll_st    ;

wire          run_st         ;

wire          slave_run_st   ;

reg           pll_done       ;

reg [11:0]         pll_count      ;

reg [2:0]          clkgen_ps      ;

reg           gen_resetn     ; // internally generated reset

reg           risc_reset      ; // internally generated reset

assign        clkout = app_clk;

wire          pllout;

/***********************************************

 Alternal PLL pr-programmed for xtal: 25Mhz , clkout 250Mhz

*********************************************************/

/*******************

altera_stargate_pll u_pll (

        . areset     (!reset_n ),

        . inclk0     (xtal_clk),

        . c0         (pllout),

        . locked     ()

       );

*************************/

assign pllout = xtal_clk;

//---------------------------------------------

//

// 100us use 25.000 Mhz clock, counter = 2500(0x9C4)

//--------------------------------------------

always @(posedge xtal_clk or negedge reset_n)

   begin // {

      if (!reset_n)

      begin // {

         pll_count <= 12'h9C4;

      end   // }                                                                 

      else if (configure_st)

      begin // {

         pll_count <= (fastsim_mode) ? 12'h040  :  12'h9C4;

      end // }

      else if (wait_pll_st)

      begin // {

         pll_count <= (pll_done) ? pll_count : (pll_count - 1'b1);

     end // }

   end // }

/************************************************

    PLL Timer Counter

************************************************/

always @(posedge xtal_clk or negedge reset_n)

begin

   if (!reset_n)

      pll_done <= 0;

   else if (pll_count == 16'h0)

      pll_done <= 1;

   else if (configure_st)

      pll_done <= 0;

end

/************************************************

  internally generated reset

************************************************/

always @(posedge xtal_clk or negedge reset_n )

begin

   if (!reset_n) begin

      gen_resetn  <=  0;

      risc_reset  <=  1;

   end else if(run_st ) begin

      gen_resetn  <=  1;

      risc_reset  <=  0;

   end else if(slave_run_st ) begin

      gen_resetn  <=  1;

      risc_reset  <=  1; // Keet Risc in Reset

   end else begin

      gen_resetn  <=  0;

      risc_reset  <=  1;

   end

end

/****************************************

    Reset State Machine

****************************************/

/*****************************************

   Define Clock Gen stat machine state

*****************************************/

`define HARD_RESET      3'b000

`define CONFIGURE       3'b001

`define WAIT_PLL        3'b010

`define RUN             3'b011

`define SLAVE_RUN       3'b100

assign hard_reset_st     = (clkgen_ps == `HARD_RESET);

assign configure_st      = (clkgen_ps == `CONFIGURE);

assign wait_pll_st       = (clkgen_ps == `WAIT_PLL);

assign run_st            = (clkgen_ps == `RUN);

assign slave_run_st      = (clkgen_ps == `SLAVE_RUN);

always @(posedge xtal_clk or negedge reset_n)

begin

   if (!reset_n) begin

      clkgen_ps <= `HARD_RESET;

   end

   else begin

      case (clkgen_ps)

         `HARD_RESET:

            clkgen_ps <= `CONFIGURE;

          `CONFIGURE:

             clkgen_ps <= `WAIT_PLL;

         `WAIT_PLL:

           if (pll_done) begin

              if ( mastermode )

                             clkgen_ps <= `RUN;

                    else

                             clkgen_ps <= `SLAVE_RUN;

          end

      endcase

   end

end

//----------------------------------

// Generate Application clock 125Mhz

//----------------------------------

clk_ctl #(1) u_appclk (

   // Outputs

       .clk_o         (app_clk),

   // Inputs

       .mclk          (pllout),

       .reset_n       (gen_resetn),

       .clk_div_ratio (2'b00)

   );

//----------------------------------

// Generate Uart Ref Clock clock 50Mhz

// 200Mhz/(2+0) = 50Mhz

// 250Mhz/(2+3) = 50Mhz

//----------------------------------

clk_ctl #(2) u_uart_clk (

   // Outputs

       .clk_o         (uart_ref_clk),

   // Inputs

       .mclk          (pllout      ),

       .reset_n       (gen_resetn  ),

       .clk_div_ratio (3'b000      )

   );

endmodule