documentation update, added STATUS.md document

c64/kernal/setmsg.s

@@ -1,4 +1,13 @@
-; Function defined on pp272-273 of C64 Programmers Reference Guide
+
+;;
+;; Official Kernal routine, described in:
+;;
+;; - [RG64] C64 Programmer's Reference Guide   - page 298
+;; - [CM64] Compute's Mapping the Commodore 64 - page 239
+;;
+;; CPU registers that has to be preserved (see [RG64]): .A, .X, .Y
+;;
+
 setmsg:
 	sta MSGFLG
 	rts