diff --git a/Components/6821/6821.hpp b/Components/6821/6821.hpp
index fa1b7c010..ae175f626 100644
--- a/Components/6821/6821.hpp
+++ b/Components/6821/6821.hpp
@@ -26,6 +26,8 @@ enum class Control {
 	CB1,	CB2,
 };
 
+// TODO: CB2/CA2 output.
+
 template <typename PortHandlerT, int RS0Mask = 1, int RS1Mask = 2>
 class MC6821 {
 public: