Added back in the jtag bridge

Now talking over the bus instead of using dpram

rtl/core/arbiter.v

@@ -0,0 +1,138 @@
+/**
+ * Module: arbiter
+ *
+ * Description:
+ *  A look ahead, round-robing parameterized arbiter.
+ *
+ * <> request
+ *  each bit is controlled by an actor and each actor can 'request' ownership
+ *  of the shared resource by bring high its request bit.
+ *
+ * <> grant
+ *  when an actor has been given ownership of shared resource its 'grant' bit
+ *  is driven high
+ *
+ * <> select
+ *  binary representation of the grant signal (optional use)
+ *
+ * <> active
+ *  is brought high by the arbiter when (any) actor has been given ownership
+ *  of shared resource.
+ *
+ *
+ * Created: Sat Jun  1 20:26:44 EDT 2013
+ *
+ * Author:  Berin Martini // berin.martini@gmail.com
+ */
+ `ifndef _arbiter_ `define _arbiter_
+ `include "../util/clog2.vh"
+
+module arbiter
+  #(parameter
+    NUM_PORTS = 6,
+    SEL_WIDTH = ((NUM_PORTS > 1) ? `CLOG2(NUM_PORTS) : 1))
+   (input wire                  clk,
+    input wire                  rst,
+    input wire [NUM_PORTS-1:0]  request,
+    output reg [NUM_PORTS-1:0]  grant,
+    output reg [SEL_WIDTH-1:0]  select,
+    output reg                  active
+);
+
+    /**
+     * Local parameters
+     */
+
+    localparam WRAP_LENGTH = 2*NUM_PORTS;
+
+
+    // Find First 1 - Start from MSB and count downwards, returns 0 when no
+    // bit set
+    function [SEL_WIDTH-1:0] ff1 (
+        input [NUM_PORTS-1:0] in
+    );
+        reg     set;
+        integer i;
+
+        begin
+            set = 1'b0;
+            ff1 = 'b0;
+
+            for (i = 0; i < NUM_PORTS; i = i + 1) begin
+                if (in[i] & ~set) begin
+                    set = 1'b1;
+                    ff1 = i[0 +: SEL_WIDTH];
+                end
+            end
+        end
+    endfunction
+
+
+`ifdef VERBOSE
+    initial $display("Bus arbiter with %d units", NUM_PORTS);
+`endif
+
+
+    /**
+     * Internal signals
+     */
+
+    integer                 yy;
+
+    wire                    next;
+    wire [NUM_PORTS-1:0]    order;
+
+    reg  [NUM_PORTS-1:0]    token;
+    wire [NUM_PORTS-1:0]    token_lookahead [NUM_PORTS-1:0];
+    wire [WRAP_LENGTH-1:0]  token_wrap;
+
+
+    /**
+     * Implementation
+     */
+
+    assign token_wrap   = {token, token};
+
+    assign next         = ~|(token & request);
+
+
+    always @(posedge clk)
+        grant <= token & request;
+
+
+    always @(posedge clk)
+        select <= ff1(token & request);
+
+
+    always @(posedge clk)
+        active <= |(token & request);
+
+
+    always @(posedge clk)
+        if (rst) token <= 'b1;
+        else if (next) begin
+
+            for (yy = 0; yy < NUM_PORTS; yy = yy + 1) begin : TOKEN_
+
+                if (order[yy]) begin
+                    token <= token_lookahead[yy];
+                end
+            end
+        end
+
+
+    genvar xx;
+    generate
+        for (xx = 0; xx < NUM_PORTS; xx = xx + 1) begin : ORDER_
+
+            assign token_lookahead[xx]  = token_wrap[xx +: NUM_PORTS];
+
+            assign order[xx]            = |(token_lookahead[xx] & request);
+
+        end
+    endgenerate
+
+
+endmodule
+
+`endif //  `ifndef _arbiter_