Merge branch 'master' of https://github.gatech.edu/casl/Vortex

hw/rtl/libs/VX_fair_arbiter.v

@@ -0,0 +1,68 @@
+`include "VX_define.vh"
+
+module VX_fair_arbiter #(
+    parameter N = 0
+) (
+    input  wire                  clk,
+    input  wire                  reset,
+    input  wire [N-1:0]          requests,           
+    output wire [`LOG2UP(N)-1:0] grant_index,
+    output wire [N-1:0]          grant_onehot,   
+    output wire                  grant_valid
+  );
+
+
+    if (N == 1)  begin        
+        
+        `UNUSED_VAR (clk)
+        `UNUSED_VAR (reset)
+        assign grant_index  = 0;
+        assign grant_onehot = requests;
+        assign grant_valid  = requests[0];
+
+    end else begin
+    
+
+       reg  [N-1:0] requests_use;
+       wire [N-1:0] update_value;
+
+       wire         refill;
+       wire [N-1:0] refill_value;
+       reg  [N-1:0] refill_original;
+
+       always @(posedge clk) begin
+            if (reset) begin
+                requests_use    <= 0;
+                refill_original <= 0;
+            end else if (refill) begin
+                requests_use    <= refill_value;
+                refill_original <= refill_value;
+            end else begin
+                requests_use <= update_value;
+            end
+       end
+
+       assign refill       = (requests_use == 0);
+       assign refill_value = requests;
+        
+        reg [N-1:0] grant_onehot_r; 
+
+        VX_priority_encoder # (
+            .N(N)
+        ) priority_encoder (
+            .data_in   (requests_use),
+            .data_out  (grant_index ),
+            .valid_out (grant_valid )
+        );
+
+        always @(*) begin
+            grant_onehot_r = N'(0);
+            grant_onehot_r[grant_index] = 1;
+        end
+        assign grant_onehot = grant_onehot_r;    
+       
+        assign update_value = (requests_use & ~grant_onehot_r) | ((refill_original ^ requests) & ~refill_original);
+
+    end
+    
+endmodule