vibed jtagram with script as drop in replacement of serving_ram

rtl/arch/spartan-6/jtag_tap_spartan6.v

@@ -0,0 +1,49 @@
+`default_nettype none
+
+// Spartan-6 JTAG TAP wrapper with an architecture-neutral interface.
+// Re-implement this module for other FPGA families with the same port list.
+module jtag_tap_spartan6
+  #(parameter USER_CHAIN = 1)
+   (
+    output wire o_drck,
+    output wire o_capture,
+    output wire o_shift,
+    output wire o_update,
+    output wire o_reset,
+    output wire o_sel,
+    output wire o_tdi,
+    input wire  i_tdo
+    );
+
+   wire drck1;
+   wire drck2;
+   wire sel1;
+   wire sel2;
+   wire tdo1;
+   wire tdo2;
+
+   localparam USE_CHAIN2 = (USER_CHAIN == 2);
+
+   assign o_drck = USE_CHAIN2 ? drck2 : drck1;
+   assign o_sel  = USE_CHAIN2 ? sel2  : sel1;
+   assign tdo1   = USE_CHAIN2 ? 1'b0  : i_tdo;
+   assign tdo2   = USE_CHAIN2 ? i_tdo : 1'b0;
+
+   BSCAN_SPARTAN6
+     #(.JTAG_CHAIN(USER_CHAIN))
+   bscan_spartan6
+     (
+      .CAPTURE(o_capture),
+      .DRCK1(drck1),
+      .DRCK2(drck2),
+      .RESET(o_reset),
+      .SEL1(sel1),
+      .SEL2(sel2),
+      .SHIFT(o_shift),
+      .TDI(o_tdi),
+      .UPDATE(o_update),
+      .TDO1(tdo1),
+      .TDO2(tdo2)
+      );
+
+endmodule