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/////////////////////////////////////////////////////////////////////
////                                                             ////
////  WISHBONE Slave Model                                       ////
////                                                             ////
////                                                             ////
////  Author: Rudolf Usselmann                                   ////
////          rudi@asics.ws                                      ////
////                                                             ////
////                                                             ////
/////////////////////////////////////////////////////////////////////
////                                                             ////
//// Copyright (C) 2001 Rudolf Usselmann                         ////
////                    rudi@asics.ws                            ////
////                                                             ////
//// 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 SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     ////
//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   ////
//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   ////
//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR      ////
//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,         ////
//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES    ////
//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE   ////
//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR        ////
//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF  ////
//// LIABILITY, WHETHER IN  CONTRACT, STRICT LIABILITY, OR TORT  ////
//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT  ////
//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE         ////
//// POSSIBILITY OF SUCH DAMAGE.                                 ////
////                                                             ////
/////////////////////////////////////////////////////////////////////
 
//  CVS Log
//
//  $Id: wb_slv_model.v,v 1.1 2001-08-16 10:01:05 rudi Exp $
//
//  $Date: 2001-08-16 10:01:05 $
//  $Revision: 1.1 $
//  $Author: rudi $
//  $Locker:  $
//  $State: Exp $
//
// Change History:
//               $Log: not supported by cvs2svn $
//
//
//
 
/* USAGE
 
wb_slv #(mem_addr_bus_width)
	<unit #>(clk, rst, adr, din, dout, cyc, stb, sel, we, ack, err, rty);
 
The parameter "mem_addr_bus_width" indicates the size of the memory by
specifiying the number of address lines to the memory.
 
task fill_mem(mode);
- This task initializes the internal memory.
  If mode is 0, the memory is initialized to  { ~address[15:0], address[15:0] };
  If mode is 1, the memory is initialized to random values.
 
 
The internal register "delay" specifies how fast ack is generated by the slave.
A value of 0 indicated immediatly, a value of 1 1 cycle delay etc.
It can be accesset by:
<wb_slv_unit_id>.delay = 5 bit value
 
*/
 
`include "wb_model_defines.v"
 
module wb_slv(clk, rst, adr, din, dout, cyc, stb, sel, we, ack, err, rty);
 
input		clk, rst;
input	[31:0]	adr, din;
output	[31:0]	dout;
input		cyc, stb;
input	[3:0]	sel;
input		we;
output		ack, err, rty;
 
////////////////////////////////////////////////////////////////////
//
// Local Wires
//
 
parameter	mem_size = 13;
parameter	sz = (1<<mem_size)-1;
 
reg	[31:0]	mem[sz:0];
wire		mem_re, mem_we;
wire	[31:0]	tmp;
reg	[31:0]	dout, tmp2;
 
reg		err, rty;
reg	[31:0]	del_ack;
reg	[5:0]	delay;
 
////////////////////////////////////////////////////////////////////
//
// Memory Logic
//
 
initial
   begin
	delay = 0;
	err = 0;
	rty = 0;
	#2;
	$display("\nINFO: WISHBONE MEMORY MODEL INSTANTIATED (%m)");
	$display("      Memory Size %0d address lines %0d words\n",
		mem_size, sz+1);
   end
 
assign mem_re = cyc & stb & !we;
assign mem_we = cyc & stb &  we;
 
assign	tmp = mem[adr[mem_size+1:2]];
 
always @(sel or tmp or mem_re or ack)
	if(mem_re & ack)
	   begin
		dout[31:24] <= #1 sel[3] ? tmp[31:24] : 8'hxx;
		dout[23:16] <= #1 sel[2] ? tmp[23:16] : 8'hxx;
		dout[15:08] <= #1 sel[1] ? tmp[15:08] : 8'hxx;
		dout[07:00] <= #1 sel[0] ? tmp[07:00] : 8'hxx;
	   end
	else	dout <= #1 32'hzzzz_zzzz;
 
 
always @(sel or tmp or din)
   begin
	tmp2[31:24] = !sel[3] ? tmp[31:24] : din[31:24];
	tmp2[23:16] = !sel[2] ? tmp[23:16] : din[23:16];
	tmp2[15:08] = !sel[1] ? tmp[15:08] : din[15:08];
	tmp2[07:00] = !sel[0] ? tmp[07:00] : din[07:00];
   end
 
always @(posedge clk)
	if(mem_we)	mem[adr[mem_size+1:2]] <= #1 tmp2;
 
always @(posedge clk)
	del_ack = ack ? 0 : {del_ack[30:0], (mem_re | mem_we)};
 
assign	#3 ack = cyc & ((delay==0) ? (mem_re | mem_we) : del_ack[delay-1]);
 
task fill_mem;
input		mode;
 
integer		n, mode;
 
begin
 
for(n=0;n<(sz+1);n=n+1)
   begin
	case(mode)
	   0:	mem[n] = { ~n[15:0], n[15:0] };
	   1:	mem[n] = $random;
	endcase
   end
 
end
endtask
 
endmodule