add important note to byte_reverse's docs

diff --git a/src/nmutil/byterev.py b/src/nmutil/byterev.py
index b0c9daf4afa61ed3aaeef570eb228b217a8383cb..a7f0a68aeacc1fd78609dcc9b60734c79e105381 100644 (file)
--- a/src/nmutil/byterev.py
+++ b/src/nmutil/byterev.py
@@ -15,6 +15,8 @@ def byte_reverse(m, name, data, length):
 
     nmigen Signal.word_select may only take a fixed length.  we need
     bigendian byte-reverse, half-word reverse, word and dword reverse.
+
+    This only outputs the first `length` bytes, higher bytes are zeroed.
     """
     comb = m.d.comb
     data_r = Signal.like(data, name=name)