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[/] [sparc64soc/] [trunk/] [WB/] [wb_conbus_arb.v] - Rev 2
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///////////////////////////////////////////////////////////////////// //// //// //// General Round Robin Arbiter //// //// //// //// //// //// Author: Rudolf Usselmann //// //// rudi@asics.ws //// //// //// //// //// //// Downloaded from: http://www.opencores.org/cores/wb_conmax/ //// //// //// ///////////////////////////////////////////////////////////////////// //// //// //// Copyright (C) 2000-2002 Rudolf Usselmann //// //// www.asics.ws //// //// 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. //// //// //// ///////////////////////////////////////////////////////////////////// // // copy from wb_conmax // // // // // `include "wb_conbus_defines.v" module wb_conbus_arb(clk, rst, req, gnt); input clk; input rst; input [7:0] req; // Req input output [2:0] gnt; // Grant output //input next; // Next Target /////////////////////////////////////////////////////////////////////// // // Parameters // parameter [2:0] grant0 = 3'h0, grant1 = 3'h1, grant2 = 3'h2, grant3 = 3'h3, grant4 = 3'h4, grant5 = 3'h5, grant6 = 3'h6, grant7 = 3'h7; /////////////////////////////////////////////////////////////////////// // // Local Registers and Wires // reg [2:0] state, next_state; /////////////////////////////////////////////////////////////////////// // // Misc Logic // assign gnt = state; always@(posedge clk or posedge rst) if(rst) state <= #1 grant0; else state <= #1 next_state; /////////////////////////////////////////////////////////////////////// // // Next State Logic // - implements round robin arbitration algorithm // - switches grant if current req is dropped or next is asserted // - parks at last grant // always@(state or req ) begin next_state = state; // Default Keep State case(state) // synopsys parallel_case full_case grant0: // if this req is dropped or next is asserted, check for other req's if(!req[0] ) begin if(req[1]) next_state = grant1; else if(req[2]) next_state = grant2; else if(req[3]) next_state = grant3; else if(req[4]) next_state = grant4; else if(req[5]) next_state = grant5; else if(req[6]) next_state = grant6; else if(req[7]) next_state = grant7; end grant1: // if this req is dropped or next is asserted, check for other req's if(!req[1] ) begin if(req[2]) next_state = grant2; else if(req[3]) next_state = grant3; else if(req[4]) next_state = grant4; else if(req[5]) next_state = grant5; else if(req[6]) next_state = grant6; else if(req[7]) next_state = grant7; else if(req[0]) next_state = grant0; end grant2: // if this req is dropped or next is asserted, check for other req's if(!req[2] ) begin if(req[3]) next_state = grant3; else if(req[4]) next_state = grant4; else if(req[5]) next_state = grant5; else if(req[6]) next_state = grant6; else if(req[7]) next_state = grant7; else if(req[0]) next_state = grant0; else if(req[1]) next_state = grant1; end grant3: // if this req is dropped or next is asserted, check for other req's if(!req[3] ) begin if(req[4]) next_state = grant4; else if(req[5]) next_state = grant5; else if(req[6]) next_state = grant6; else if(req[7]) next_state = grant7; else if(req[0]) next_state = grant0; else if(req[1]) next_state = grant1; else if(req[2]) next_state = grant2; end grant4: // if this req is dropped or next is asserted, check for other req's if(!req[4] ) begin if(req[5]) next_state = grant5; else if(req[6]) next_state = grant6; else if(req[7]) next_state = grant7; else if(req[0]) next_state = grant0; else if(req[1]) next_state = grant1; else if(req[2]) next_state = grant2; else if(req[3]) next_state = grant3; end grant5: // if this req is dropped or next is asserted, check for other req's if(!req[5] ) begin if(req[6]) next_state = grant6; else if(req[7]) next_state = grant7; else if(req[0]) next_state = grant0; else if(req[1]) next_state = grant1; else if(req[2]) next_state = grant2; else if(req[3]) next_state = grant3; else if(req[4]) next_state = grant4; end grant6: // if this req is dropped or next is asserted, check for other req's if(!req[6] ) begin if(req[7]) next_state = grant7; else if(req[0]) next_state = grant0; else if(req[1]) next_state = grant1; else if(req[2]) next_state = grant2; else if(req[3]) next_state = grant3; else if(req[4]) next_state = grant4; else if(req[5]) next_state = grant5; end grant7: // if this req is dropped or next is asserted, check for other req's if(!req[7] ) begin if(req[0]) next_state = grant0; else if(req[1]) next_state = grant1; else if(req[2]) next_state = grant2; else if(req[3]) next_state = grant3; else if(req[4]) next_state = grant4; else if(req[5]) next_state = grant5; else if(req[6]) next_state = grant6; end endcase end endmodule