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[/] [sparc64soc/] [trunk/] [WB/] [wb_conbus_arb.v] - Blame information for rev 5

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1 2 dmitryr
/////////////////////////////////////////////////////////////////////
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////                                                             ////
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////  General Round Robin Arbiter                                ////
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////                                                             ////
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////                                                             ////
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////  Author: Rudolf Usselmann                                   ////
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////          rudi@asics.ws                                      ////
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////                                                             ////
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////                                                             ////
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////  Downloaded from: http://www.opencores.org/cores/wb_conmax/ ////
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////                                                             ////
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/////////////////////////////////////////////////////////////////////
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////                                                             ////
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//// Copyright (C) 2000-2002 Rudolf Usselmann                    ////
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////                         www.asics.ws                        ////
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////                         rudi@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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//
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//      copy from wb_conmax
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//
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//
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//
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//
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//                        
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`include "wb_conbus_defines.v"
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module wb_conbus_arb(clk, rst, req, gnt);
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input           clk;
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input           rst;
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input   [7:0]    req;            // Req input
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output  [2:0]    gnt;            // Grant output
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//input         next;           // Next Target
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///////////////////////////////////////////////////////////////////////
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//
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// Parameters
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//
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parameter       [2:0]
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                grant0 = 3'h0,
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                grant1 = 3'h1,
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                grant2 = 3'h2,
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                grant3 = 3'h3,
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                grant4 = 3'h4,
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                grant5 = 3'h5,
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                grant6 = 3'h6,
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                grant7 = 3'h7;
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///////////////////////////////////////////////////////////////////////
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//
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// Local Registers and Wires
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//
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reg [2:0]        state, next_state;
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///////////////////////////////////////////////////////////////////////
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//
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//  Misc Logic 
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//
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assign  gnt = state;
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always@(posedge clk or posedge rst)
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        if(rst)         state <= #1 grant0;
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        else            state <= #1 next_state;
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///////////////////////////////////////////////////////////////////////
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//
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// Next State Logic
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//   - implements round robin arbitration algorithm
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//   - switches grant if current req is dropped or next is asserted
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//   - parks at last grant
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//
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always@(state or req )
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   begin
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        next_state = state;     // Default Keep State
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        case(state)             // synopsys parallel_case full_case
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           grant0:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[0] )
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                   begin
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                        if(req[1])      next_state = grant1;
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                        else
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                        if(req[2])      next_state = grant2;
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                        else
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                        if(req[3])      next_state = grant3;
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                        else
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                        if(req[4])      next_state = grant4;
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                        else
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                        if(req[5])      next_state = grant5;
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                        else
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                        if(req[6])      next_state = grant6;
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                        else
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                        if(req[7])      next_state = grant7;
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                   end
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           grant1:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[1] )
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                   begin
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                        if(req[2])      next_state = grant2;
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                        else
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                        if(req[3])      next_state = grant3;
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                        else
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                        if(req[4])      next_state = grant4;
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                        else
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                        if(req[5])      next_state = grant5;
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                        else
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                        if(req[6])      next_state = grant6;
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                        else
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                        if(req[7])      next_state = grant7;
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                        else
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                        if(req[0])       next_state = grant0;
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                   end
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           grant2:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[2] )
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                   begin
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                        if(req[3])      next_state = grant3;
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                        else
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                        if(req[4])      next_state = grant4;
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                        else
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                        if(req[5])      next_state = grant5;
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                        else
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                        if(req[6])      next_state = grant6;
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                        else
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                        if(req[7])      next_state = grant7;
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                        else
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                        if(req[0])       next_state = grant0;
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                        else
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                        if(req[1])      next_state = grant1;
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                   end
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           grant3:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[3] )
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                   begin
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                        if(req[4])      next_state = grant4;
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                        else
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                        if(req[5])      next_state = grant5;
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                        else
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                        if(req[6])      next_state = grant6;
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                        else
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                        if(req[7])      next_state = grant7;
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                        else
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                        if(req[0])       next_state = grant0;
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                        else
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                        if(req[1])      next_state = grant1;
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                        else
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                        if(req[2])      next_state = grant2;
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                   end
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           grant4:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[4] )
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                   begin
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                        if(req[5])      next_state = grant5;
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                        else
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                        if(req[6])      next_state = grant6;
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                        else
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                        if(req[7])      next_state = grant7;
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                        else
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                        if(req[0])       next_state = grant0;
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                        else
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                        if(req[1])      next_state = grant1;
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                        else
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                        if(req[2])      next_state = grant2;
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                        else
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                        if(req[3])      next_state = grant3;
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                   end
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           grant5:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[5] )
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                   begin
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                        if(req[6])      next_state = grant6;
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                        else
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                        if(req[7])      next_state = grant7;
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                        else
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                        if(req[0])       next_state = grant0;
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                        else
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                        if(req[1])      next_state = grant1;
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                        else
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                        if(req[2])      next_state = grant2;
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                        else
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                        if(req[3])      next_state = grant3;
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                        else
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                        if(req[4])      next_state = grant4;
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                   end
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           grant6:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[6] )
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                   begin
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                        if(req[7])      next_state = grant7;
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                        else
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                        if(req[0])       next_state = grant0;
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                        else
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                        if(req[1])      next_state = grant1;
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                        else
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                        if(req[2])      next_state = grant2;
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                        else
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                        if(req[3])      next_state = grant3;
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                        else
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                        if(req[4])      next_state = grant4;
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                        else
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                        if(req[5])      next_state = grant5;
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                   end
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           grant7:
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                // if this req is dropped or next is asserted, check for other req's
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                if(!req[7] )
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                   begin
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                        if(req[0])       next_state = grant0;
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                        else
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                        if(req[1])      next_state = grant1;
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                        else
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                        if(req[2])      next_state = grant2;
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                        else
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                        if(req[3])      next_state = grant3;
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                        else
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                        if(req[4])      next_state = grant4;
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                        else
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                        if(req[5])      next_state = grant5;
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                        else
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                        if(req[6])      next_state = grant6;
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                   end
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        endcase
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   end
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endmodule
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