round robin arbiter + auto buffered queue + fixed dcache arbiter

hw/rtl/libs/VX_fixed_arbiter.v

@@ -0,0 +1,43 @@
+`include "VX_define.vh"
+
+module VX_fixed_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
+  );
+
+    `UNUSED_VAR (clk)
+    `UNUSED_VAR (reset)
+
+    if (N == 1)  begin        
+        
+        assign grant_index  = 0;
+        assign grant_onehot = requests;
+        assign grant_valid  = requests[0];
+
+    end else begin
+    
+        reg [N-1:0] grant_onehot_r; 
+
+        VX_priority_encoder # (
+            .N(N)
+        ) priority_encoder (
+            .data_in   (requests),
+            .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;    
+        
+    end
+    
+endmodule