Connect tdi to tdo for boundary scan without IOs.

[c4m-jtag.git] / c4m / nmigen / jtag / tap.py

diff --git a/c4m/nmigen/jtag/tap.py b/c4m/nmigen/jtag/tap.py
index 13a78b235b7310bce65c0868cb3d33f69509692d..a6b702fd7786c751355eac1f2a0ab92a8307c53a 100755 (executable)
--- a/c4m/nmigen/jtag/tap.py
+++ b/c4m/nmigen/jtag/tap.py
@@ -438,6 +438,8 @@ class TAP(Elaboratable):
             IOType.InTriOut: 3,
         }
         length = sum(connlength[conn._iotype] for conn in self._ios)
+        if length == 0:
+            return self.bus.tdi
 
         io_sr = Signal(length)
         io_bd = Signal(length)
@@ -499,7 +501,6 @@ class TAP(Elaboratable):
 
         return io_sr[-1]
 
-
     def add_shiftreg(self, *, ircode, length, domain="sync", name=None, src_loc_at=0):
         """Add a shift register to the JTAG interface