ref_ack.v

嵌入式risc处理器源码

/*********************************************************
 MODULE:		Sub Level SDRAM Refresh Acknowledge

 FILE NAME:	ref_ack.v
 VERSION:	1.0
 DATE:		April 28th, 2002
 AUTHOR:		Hossein Amidi
 COMPANY:	
 CODE TYPE:	Register Transfer Level

 DESCRIPTION:	This module is the sub level RTL code of SDRAM Controller ASIC verilog
 code. It is the Refresh Acknowledge block.


 Hossein Amidi
 (C) April 2002

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

// DEFINES
`timescale 1ns / 10ps

module ref_ack(// Input
					reset,
					clk0,
					do_refresh,
					do_reada,
					do_writea,
					do_preacharge,
					do_load_mod,
					ref_req,
					// Output
					cmack,
					ref_ack
					);

// Parameter
`include        "parameter.v"

// Input
input reset;
input clk0;
input do_refresh;
input do_reada;
input do_writea;
input do_preacharge;
input do_load_mod;
input ref_req;

// Output
output cmack;
output ref_ack;

// Internal wire and reg signals
wire reset;
wire clk0;
wire do_refresh;
wire do_reada;
wire do_writea;
wire do_preacharge;
wire do_load_mod;
wire ref_req;

reg	cmack;
reg   ref_ack;

// Assignment

// This always block generates the command acknowledge, cmack, signal.
// It also generates the acknowledge signal, ref_ack, that acknowledges
// a refresh request that was generated by the internal refresh timer circuit.
always @(posedge reset or posedge clk0) 
begin

        if (reset == 1'b1) 
        begin
                cmack    <= 0;
                ref_ack  <= 0;
        end
        
        else
        begin
                if (do_refresh == 1 & ref_req == 1)                   // Internal refresh timer refresh request
                        ref_ack <= 1;
                else if ((do_refresh == 1) | (do_reada == 1) | (do_writea == 1) | (do_preacharge == 1)   // externa  commands
                         | (do_load_mod))
                        cmack <= 1;
                else
                begin
                        ref_ack <= 0;
                        cmack   <= 0;
                end
        end
end 


endmodule