documentation update, added STATUS.md document

c64/kernal/save.s

@@ -1,3 +1,13 @@
-; Function defined on pp272-273 of C64 Programmers Reference Guide
+
+;;
+;; Official Kernal routine, described in:
+;;
+;; - [RG64] C64 Programmer's Reference Guide   - page 293/294
+;; - [CM64] Compute's Mapping the Commodore 64 - page 231/232
+;; - IEC reference at http://www.zimmers.net/anonftp/pub/cbm/programming/serial-bus.pdf
+;;
+;; CPU registers that has to be preserved (see [RG64]): none
+;;
+
 save:
 	rts