Added JTAG interface with testbench

rtl/core/jtag_if.v

@@ -0,0 +1,34 @@
+`timescale 1ns/1ps
+
+// =============================================================================
+// JTAG interface
+// Generic stub model with inactive/tied-off outputs.
+// =============================================================================
+module jtag_if #(
+    parameter chain = 1
+)(
+    input wire i_tdo,
+    output wire o_tck,
+    output wire o_tdi,
+    output wire o_drck,
+    output wire o_capture,
+    output wire o_shift,
+    output wire o_update,
+    output wire o_runtest,
+    output wire o_reset,
+    output wire o_sel
+);
+    assign o_tck = 1'b0;
+    assign o_tdi = 1'b0;
+    assign o_drck = 1'b0;
+    assign o_capture = 1'b0;
+    assign o_shift = 1'b0;
+    assign o_update = 1'b0;
+    assign o_runtest = 1'b0;
+    assign o_reset = 1'b0;
+    assign o_sel = 1'b0;
+
+    // Keep lint tools quiet in generic builds where TDO is unused.
+    wire _unused_tdo;
+    assign _unused_tdo = i_tdo;
+endmodule