documentation update, added STATUS.md document

c64/kernal/stop.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 301
+;; - [CM64] Compute's Mapping the Commodore 64 - page 232
+;;
+;; CPU registers that has to be preserved (see [RG64]): .Y
+;;
+
 stop:
 	;; Bit 7 of BUCKYSTATUS contains the state of the STOP key
 	;; (Compute's Mapping the 64, p27)
@@ -8,10 +17,10 @@ stop:
 	and #$80
 	beq stop_pressed
 
-	;;  By trial and error, we know that Z + C = BREAK
+	;; By trial and error, we know that Z + C = BREAK
 	;; and that neither should be set otherwise
 	lda #$ff
-	clc	
+	clc
 	rts
 
 stop_pressed: