ram_sync_1r_sync_1w.v

a H.264/AVC Baseline Decoder

//--------------------------------------------------------------------------------------------------
// Design    : nova
// Author(s) : Ke Xu
// Email	   : [e-mail]
// File      : ram_sync_1r_sync_1w.v
// Generated : April 25,2005
// Copyright (C) 2008 Ke Xu                
//-------------------------------------------------------------------------------------------------
// Description 
// Synch Write, Synch Read RAM, NOT synthesizable
// In real silicon, use customized RAM instead of DFF  
// legal range:data_width   [ 1 to 256 ]
// legal range:data_depth   [ 2 to 1024 ]
// 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_sync_1r_sync_1w (clk, rst_n, wr_n, rd_n, wr_addr, rd_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>32)?((data_depth>256)?((data_depth>512)?10:9):((data_depth>128)?8:((data_depth>64)?7:6))):((data_depth>8)  ?((data_depth>16) ?5:4) :((data_depth>4)  ?3:((data_depth>2) ?1:0))))
  
  input clk;
  input rst_n;
  input wr_n;
  input rd_n; 
  input [`addr_width-1:0] wr_addr;
  input [`addr_width-1:0] rd_addr;
  input  [data_width-1:0] data_in;
  output [data_width-1:0] data_out;
  
  reg [data_width-1:0] data_out; 
  reg [data_width-1:0] ram [data_depth-1:0];
  
  //data_width, data_depth, simultaneously read/write check
  initial 
  	begin:parameter_check
    	integer param_error_flag;
    	param_error_flag = 0;
    
      if ( (data_width < 1) || (data_width > 256) ) 
    		begin
      		param_error_flag = 1;
      		$display("Error: %m :\n  Invalid value (%d) for parameter data_width (legal range: 1 to 256)",data_width );
    		end
  
    	if ( (data_depth < 2) || (data_depth > 1024 ) ) 
    		begin
      		param_error_flag = 1;
      		$display("Error: %m :\n  Invalid value (%d) for parameter data_depth (legal range: 2 to 1024 )",data_depth );
    		end
    	
    	/* 
    	if ( (cs_n == 1'b0 && wr_n == 1'b0 && rd_n == 1'b0 ) )
    		begin
    			param_error_flag = 1;
    			$display("Error: %m :\n  Not allowed! RAM simultaneously read and write occur");
    		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
  always @ (posedge clk or negedge rst_n)
  	if (rst_n == 1'b0)
  		data_out <= 0;
  	else if (!rd_n)
  		data_out <= ram[rd_addr];
      
	//write
	always @ (posedge clk)
		if (!wr_n)
			ram[wr_addr] <= data_in;
			
endmodule