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

// Design    : nova

// Author(s) : Ke Xu

// Email           : eexuke@yahoo.com

// File      : ram_async_1r_sync_1w.v

// Generated : April 25,2005

// Copyright (C) 2008 Ke Xu                

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

// Description 

// Synch Write, Asynch Read RAM, NOT synthesizable

// In real silicon, use register file (DFF) instead of RAM 

// legal range:data_width   [ 1 to 128 ]

// legal range:data_depth   [ 2 to 256 ]

// Input data :data_in[data_width-1:0]

// Output data:data_out[data_width-1:0]

// Read Address :rd_addr[addr_width-1:0]

// Write Address:wr_addr[addr_width-1:0]

// Write enable (active low): wr_n

// Chip select (active low): cs_n

// Reset (active low): rst_n

// Clock:clk

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

// synopsys translate_off

`include "timescale.v"

// synopsys translate_on

`include "nova_defines.v"

module ram_async_1r_sync_1w (clk, rst_n, cs_n, wr_n, rd_addr, wr_addr, data_in, data_out);

  parameter data_width = 4;     //will be overrided during module instantiation

  parameter data_depth = 8; //will be overrided during module instantiation

  `define addr_width ((data_depth>16)?((data_depth>64)?((data_depth>128)?8:7):((data_depth>32)?6:5)):((data_depth>4)?((data_depth>8)?4:3):((data_depth>2)?2:1)))

  input clk;

  input rst_n;

  input cs_n;

  input wr_n;

  input [data_width-1:0] data_in;

  input [`addr_width-1:0] rd_addr;

  input [`addr_width-1:0] wr_addr;

  output [data_width-1:0] data_out;

  reg [data_width-1:0] ram [data_depth-1:0];

  //data_width & data_depth check

  initial

        begin:parameter_check

        integer param_error_flag;

        param_error_flag = 0;

      if ( (data_width < 1) || (data_width > 128) )

                begin

                param_error_flag = 1;

                $display("Error: %m :\n  Invalid value (%d) for parameter data_width (legal range: 1 to 128)",data_width );

                end

        if ( (data_depth < 2) || (data_depth > 256 ) )

                begin

                param_error_flag = 1;

                $display("Error: %m :\n  Invalid value (%d) for parameter data_depth (legal range: 2 to 256 )",data_depth );

                end

        if ( param_error_flag == 1)

                begin

                $display("%m :\n  Simulation aborted due to invalid parameter value(s)");

                $finish;

                end

        end // end data_width & data_depth check

  //read

  assign data_out = ((rd_addr ^ rd_addr) !== {`addr_width{1'b0}})? {data_width{1'bx}} : ((rd_addr >= data_depth)? {data_width{1'b0}} : ram[rd_addr] );

        //write

        always @ (posedge clk)

                if (!cs_n && !wr_n)

                        ram[wr_addr] <= data_in;

endmodule