vendor.lattice_ice40: reword confusing comment. NFC.

diff --git a/nmigen/vendor/lattice_ice40.py b/nmigen/vendor/lattice_ice40.py
index 4617d0374b8a389f8e6626faa7e183e61543ef4b..fcfa1c0ffdc8754a7866bbda615886a9201f7aec 100644 (file)
--- a/nmigen/vendor/lattice_ice40.py
+++ b/nmigen/vendor/lattice_ice40.py
@@ -620,8 +620,8 @@ class LatticeICE40Platform(TemplatedPlatform):
         self._get_io_buffer(m, pin, n_port, attrs, o_invert=not invert, invert_lut=True)
         return m
 
-    # Tristate and bidirectional buffers are not supported on iCE40 because it requires external
-    # termination, which is incompatible for input and output differential I/Os.
+    # Tristate bidirectional buffers are not supported on iCE40 because it requires external
+    # termination, which is different for differential pins configured as inputs and outputs.
 
     # CDC primitives are not currently specialized for iCE40. It is not known if iCECube2 supports
     # the necessary attributes; nextpnr-ice40 does not.