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authorClifford Wolf <clifford@clifford.at>2013-01-05 11:13:26 +0100
committerClifford Wolf <clifford@clifford.at>2013-01-05 11:13:26 +0100
commit7764d0ba1dcf064ae487ee985c43083a0909e7f4 (patch)
tree18c05b8729df381af71b707748ce1d605e0df764 /tests/asicworld/code_hdl_models_arbiter.v
initial import
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+//----------------------------------------------------
+// A four level, round-robin arbiter. This was
+// orginally coded by WD Peterson in VHDL.
+//----------------------------------------------------
+module arbiter (
+ clk,
+ rst,
+ req3,
+ req2,
+ req1,
+ req0,
+ gnt3,
+ gnt2,
+ gnt1,
+ gnt0
+);
+// --------------Port Declaration-----------------------
+input clk;
+input rst;
+input req3;
+input req2;
+input req1;
+input req0;
+output gnt3;
+output gnt2;
+output gnt1;
+output gnt0;
+
+//--------------Internal Registers----------------------
+wire [1:0] gnt ;
+wire comreq ;
+wire beg ;
+wire [1:0] lgnt ;
+wire lcomreq ;
+reg lgnt0 ;
+reg lgnt1 ;
+reg lgnt2 ;
+reg lgnt3 ;
+reg lasmask ;
+reg lmask0 ;
+reg lmask1 ;
+reg ledge ;
+
+//--------------Code Starts Here-----------------------
+always @ (posedge clk)
+if (rst) begin
+ lgnt0 <= 0;
+ lgnt1 <= 0;
+ lgnt2 <= 0;
+ lgnt3 <= 0;
+end else begin
+ lgnt0 <=(~lcomreq & ~lmask1 & ~lmask0 & ~req3 & ~req2 & ~req1 & req0)
+ | (~lcomreq & ~lmask1 & lmask0 & ~req3 & ~req2 & req0)
+ | (~lcomreq & lmask1 & ~lmask0 & ~req3 & req0)
+ | (~lcomreq & lmask1 & lmask0 & req0 )
+ | ( lcomreq & lgnt0 );
+ lgnt1 <=(~lcomreq & ~lmask1 & ~lmask0 & req1)
+ | (~lcomreq & ~lmask1 & lmask0 & ~req3 & ~req2 & req1 & ~req0)
+ | (~lcomreq & lmask1 & ~lmask0 & ~req3 & req1 & ~req0)
+ | (~lcomreq & lmask1 & lmask0 & req1 & ~req0)
+ | ( lcomreq & lgnt1);
+ lgnt2 <=(~lcomreq & ~lmask1 & ~lmask0 & req2 & ~req1)
+ | (~lcomreq & ~lmask1 & lmask0 & req2)
+ | (~lcomreq & lmask1 & ~lmask0 & ~req3 & req2 & ~req1 & ~req0)
+ | (~lcomreq & lmask1 & lmask0 & req2 & ~req1 & ~req0)
+ | ( lcomreq & lgnt2);
+ lgnt3 <=(~lcomreq & ~lmask1 & ~lmask0 & req3 & ~req2 & ~req1)
+ | (~lcomreq & ~lmask1 & lmask0 & req3 & ~req2)
+ | (~lcomreq & lmask1 & ~lmask0 & req3)
+ | (~lcomreq & lmask1 & lmask0 & req3 & ~req2 & ~req1 & ~req0)
+ | ( lcomreq & lgnt3);
+end
+
+//----------------------------------------------------
+// lasmask state machine.
+//----------------------------------------------------
+assign beg = (req3 | req2 | req1 | req0) & ~lcomreq;
+always @ (posedge clk)
+begin
+ lasmask <= (beg & ~ledge & ~lasmask);
+ ledge <= (beg & ~ledge & lasmask)
+ | (beg & ledge & ~lasmask);
+end
+
+//----------------------------------------------------
+// comreq logic.
+//----------------------------------------------------
+assign lcomreq = ( req3 & lgnt3 )
+ | ( req2 & lgnt2 )
+ | ( req1 & lgnt1 )
+ | ( req0 & lgnt0 );
+
+//----------------------------------------------------
+// Encoder logic.
+//----------------------------------------------------
+assign lgnt = {(lgnt3 | lgnt2),(lgnt3 | lgnt1)};
+
+//----------------------------------------------------
+// lmask register.
+//----------------------------------------------------
+always @ (posedge clk )
+if( rst ) begin
+ lmask1 <= 0;
+ lmask0 <= 0;
+end else if(lasmask) begin
+ lmask1 <= lgnt[1];
+ lmask0 <= lgnt[0];
+end else begin
+ lmask1 <= lmask1;
+ lmask0 <= lmask0;
+end
+
+assign comreq = lcomreq;
+assign gnt = lgnt;
+//----------------------------------------------------
+// Drive the outputs
+//----------------------------------------------------
+assign gnt3 = lgnt3;
+assign gnt2 = lgnt2;
+assign gnt1 = lgnt1;
+assign gnt0 = lgnt0;
+
+endmodule