Subversion Repositories genesys_ddr2

`timescale 1ns / 1ps

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

// Company: UPT

// Engineer: Oana Boncalo & Alexandru Amaricai

// 

// Create Date:    15:37:02 04/10/2013 

// Design Name: 

// Module Name:    debounceRst 

// Project Name: 

// Target Devices: 

// Tool versions: 

// Description: 

//

// Dependencies: 

//

// Revision: 

// Revision 0.01 - File Created

// Additional Comments: 

//

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

module debounceRst(

    input clk,

    input noisyRst,

         input PLLLocked,

    output cleanPLLRst,

         output cleanAsyncRst

    );

         localparam NR_SAMPLES = 10;

         localparam DELAY_CC = 100;

         localparam BITS_DELAY_CC = 8;// 8 = ceil(log2(DELAY_CC));

         reg [NR_SAMPLES-1: 0]           rst_samples;

         wire                                                   rst_samples_and_N, rst_samples_and_N_1;

         reg [DELAY_CC-1: 0]             rst_debounce_delay_loop = {1'b0, {(DELAY_CC-1){1'b1}}};

         reg [BITS_DELAY_CC-1: 0]        rst_cnt_delay = 100 + 128;//100 + {1'b1, {(BITS_DELAY_CC-2){1'b0}}};     //keep reset active for DELAY_CC time

         wire                                                   async_rst, PLLRst, rst_edge, start_up_rst;

        // --4-bit Shift Register For resetting the PLL

        //--Asserts Start_Up_Rst for 4 clock periods

        SRL16E #(

      .INIT(16'h000F) // Initial Value of Shift Register

   ) SRL16E_inst (

      .Q(start_up_rst), // SRL data output

      .A0 (1'b1),       //-- Select[0] input

      .A1 (1'b1),       //-- Select[1] input

      .A2 (1'b0),       //-- Select[2] input

      .A3 (1'b0),       //-- Select[3] input

      .CE (1'b1),       // Clock enable input

      .CLK(clk),                // Clock input

      .D(1'b0)          // SRL data input

   );

         //debounce logic

         always @(posedge clk)

         begin

                rst_samples <= {rst_samples [NR_SAMPLES-2: 0],noisyRst};

         end

         assign rst_samples_and_N =  & rst_samples;

         assign rst_samples_and_N_1 = & rst_samples[NR_SAMPLES-2:0];

         //detect edge

         assign rst_edge = (rst_samples_and_N_1 && (! rst_samples_and_N))? 1'b1: 1'b0;

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

        //-- Reset with take-off and landing

        //-- delay 95 cc = DELAY_CC - 4 reset

        //-- then keep it active for 3 cc (as long as one of rst_debounce_delay_loop[DELAY_CC-2], rst_debounce_delay_loop[DELAY_CC-3] or rst_debounce_delay_loop[DELAY_CC-4] is 0)

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

         always @(posedge clk)

         begin

                if (rst_edge || rst_debounce_delay_loop[DELAY_CC-1])

                                rst_debounce_delay_loop <= {rst_debounce_delay_loop[DELAY_CC-2:0],rst_debounce_delay_loop[DELAY_CC-1]};

         end

        assign PLLRst = ((~rst_debounce_delay_loop[DELAY_CC-2]) || (~rst_debounce_delay_loop[DELAY_CC-3]) ||

                                        (~rst_debounce_delay_loop[DELAY_CC-4]) || start_up_rst)? 1'b1: 1'b0;

        assign int_rst =  ~PLLLocked;

        //decrement counter for 100 cc then rst_cnt_delay[BITS_DELAY_CC-1] becomes 0

        always @(posedge clk)

        begin

                if (int_rst)

                        rst_cnt_delay <= 228;//DELAY_CC + {1'b1, {(BITS_DELAY_CC-2){1'b0}}};

                else

                        if (rst_cnt_delay[BITS_DELAY_CC-1])

                                rst_cnt_delay <= rst_cnt_delay - 1;

         end

        assign async_rst = rst_cnt_delay[BITS_DELAY_CC-1] | rst_debounce_delay_loop[DELAY_CC -1]; //--100 cc have passed since reset signal has been generated

        assign cleanAsyncRst = async_rst;

        assign cleanPLLRst = PLLRst;

endmodule