at_ctw3.v 1.54 KB
/**************************************************************************
 *                                                                        *
 *               Copyright (C) 1994, Silicon Graphics, Inc.               *
 *                                                                        *
 *  These coded instructions, statements, and computer programs  contain  *
 *  unpublished  proprietary  information of Silicon Graphics, Inc., and  *
 *  are protected by Federal copyright  law.  They  may not be disclosed  *
 *  to  third  parties  or copied or duplicated in any form, in whole or  *
 *  in part, without the prior written consent of Silicon Graphics, Inc.  *
 *                                                                        *
 *************************************************************************/

// $Id: at_ctw3.v,v 1.1.1.1 2002/05/17 06:07:44 blythe Exp $

////////////////////////////////////////////////////////////////////////
//
// Project Reality
//
// module:      at_ctw3
// description: Counter for attribute buffers.
//
// designer:    Phil Gossett
// date:        9/6/94
//
////////////////////////////////////////////////////////////////////////

module at_ctw3 (clk, rst, enb, a, b, c);

input clk;
input rst;
input enb;

output a;
output b;
output c;

reg [1:0] z;

// counter
always @(posedge clk or posedge rst)
begin
	if (rst == 1'b1)
		z <= 2'b00;	// 0
	else
		z <= enb ? {z[0],(z == 2'b00)} : z;
end

assign a = enb & (z == 2'b00);
assign b = enb & (z == 2'b01);
assign c = enb & (z == 2'b10);

endmodule // at_ctw3