Debug regressions: use a plusarg to enable remote bitbang.

src/main/scala/devices/debug/Periphery.scala

@@ -130,7 +130,7 @@ class SimJTAG(tickDelay: Int = 50) extends BlackBox(Map("TICK_DELAY" -> IntParam
     io.clock := tbclock
     io.reset := tbreset
 
-    io.enable    := ~tbreset
+    io.enable    := PlusArg("jtag_rbb_enable", 0, "Enable SimJTAG for JTAG Connections. Simulation will pause until connection is made.")
     io.init_done := ~tbreset
 
     // Success is determined by the gdbserver