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nn-usb-fpga/lm32/logic/sakc/rtl/wb_conbus/wb_conbus_arb.v
Carlos Camargo 61d4408f2a Adding lm32 demo to SAKC project
2010-05-25 21:49:58 -05:00

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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 <= grant0;
else state <= 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
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