1 files changed, 1 insertions, 0 deletions
diff --git a/TODO b/TODO
index 818b78c3..614aaa85 100644
--- a/TODO
+++ b/TODO
@@ -27,6 +27,7 @@ Well-formed high firrtl
    UInt only has positive ints
    No combinational loops
    cannot connect to a pad, or a register. only connct to a reference
+   expression in pad must be a ground type
 After adding dynamic assertions, insert bounds check with accessor expansion
 Well-formed low firrtl
    All things only assigned to once