documentation update, added STATUS.md document

c64/kernal/talk.s

@@ -1,9 +1,20 @@
-; Function defined on pp272-273 of C64 Programmers Reference Guide
+
+;;
+;; Official Kernal routine, described in:
+;;
+;; - [RG64] C64 Programmer's Reference Guide   - page 301/302
+;; - [CM64] Compute's Mapping the Commodore 64 - page 223
+;;
+;; CPU registers that has to be preserved (see [RG64]): .X, .Y
+;;
+
+;; XXX currently does not preserve registers, to be fixed!
+;; XXX shouldn't this do a turnaround?
 
 talk:
 
-	;; This routine is documented in 'Compute's Mapping the Commodore 64', page 223 and
-	;; https://www.pagetable.com/?p=1031, , https://github.com/mist64/cbmbus_doc
+	;; See also https://www.pagetable.com/?p=1031, https://github.com/mist64/cbmbus_doc
+
 	and #$1F ; make sure bits encoding the command are cleared out
 	ora #$40
 	jmp iec_tx_command