127 lines
4.2 KiB
Coq
127 lines
4.2 KiB
Coq
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/////////////////////////////////////////////////////////////////////
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//// ////
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//// FIFO 4 entries deep ////
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//// ////
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//// Authors: Rudolf Usselmann, Richard Herveille ////
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//// rudi@asics.ws richard@asics.ws ////
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//// ////
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//// ////
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//// Download from: http://www.opencores.org/projects/sasc ////
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//// http://www.opencores.org/projects/simple_spi ////
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//// ////
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/////////////////////////////////////////////////////////////////////
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//// ////
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//// Copyright (C) 2000-2002 Rudolf Usselmann, Richard Herveille ////
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//// www.asics.ws ////
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//// rudi@asics.ws, richard@asics.ws ////
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//// ////
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//// This source file may be used and distributed without ////
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//// restriction provided that this copyright statement is not ////
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//// removed from the file and that any derivative work contains ////
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//// the original copyright notice and the associated disclaimer.////
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//// ////
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//// THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY ////
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//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED ////
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//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS ////
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//// FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL THE AUTHOR ////
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//// OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, ////
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//// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES ////
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//// (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE ////
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//// GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR ////
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//// BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF ////
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//// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ////
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//// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT ////
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//// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE ////
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//// POSSIBILITY OF SUCH DAMAGE. ////
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//// ////
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/////////////////////////////////////////////////////////////////////
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// CVS Log
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//
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// $Id: fifo4.v,v 1.1.1.1 2002-12-22 16:07:14 rherveille Exp $
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//
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// $Date: 2002-12-22 16:07:14 $
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// $Revision: 1.1.1.1 $
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// $Author: rherveille $
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// $Locker: $
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// $State: Exp $
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//
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// Change History:
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// $Log: not supported by cvs2svn $
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//
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// 4 entry deep fast fifo
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module fifo4(clk, rst, clr, din, we, dout, re, full, empty);
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parameter dw = 8;
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input clk, rst;
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input clr;
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input [dw:1] din;
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input we;
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output [dw:1] dout;
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input re;
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output full, empty;
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////////////////////////////////////////////////////////////////////
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//
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// Local Wires
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//
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reg [dw:1] mem[0:3];
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reg [1:0] wp;
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reg [1:0] rp;
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wire [1:0] wp_p1;
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wire [1:0] wp_p2;
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wire [1:0] rp_p1;
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wire full, empty;
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reg gb;
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////////////////////////////////////////////////////////////////////
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//
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// Misc Logic
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//
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always @(posedge clk or negedge rst)
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if(!rst) wp <= 2'h0;
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else
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if(clr) wp <= 2'h0;
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else
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if(we) wp <= wp_p1;
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assign wp_p1 = wp + 2'h1;
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assign wp_p2 = wp + 2'h2;
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always @(posedge clk or negedge rst)
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if(!rst) rp <= 2'h0;
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else
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if(clr) rp <= 2'h0;
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else
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if(re) rp <= rp_p1;
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assign rp_p1 = rp + 2'h1;
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// Fifo Output
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assign dout = mem[ rp ];
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// Fifo Input
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always @(posedge clk)
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if(we) mem[ wp ] <= din;
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// Status
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assign empty = (wp == rp) & !gb;
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assign full = (wp == rp) & gb;
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// Guard Bit ...
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always @(posedge clk)
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if(!rst) gb <= 1'b0;
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else
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if(clr) gb <= 1'b0;
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else
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if((wp_p1 == rp) & we) gb <= 1'b1;
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else
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if(re) gb <= 1'b0;
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endmodule
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