fix for STOP key detection

c64/kernal/f6ed.stop.s

@@ -14,8 +14,7 @@ stop:
 
 	;; BASIC checks carry flag to indicate STOP or not
 	lda STKEY
-	and #$80
+	bpl stop_pressed
-	beq stop_pressed
 
 	;; By trial and error, we know that Z + C = BREAK
 	;; and that neither should be set otherwise

c64/kernal/scnkey.s

@@ -204,6 +204,10 @@ ReturnNoKeys:
 
 NoActivityDetected:
 
+	;; Cancel STKEY status
+	lda #$FF
+	sta STKEY ; XXX this variable should be set by UDTIM
+
 	;; So cancel all bucky keys
 	lda key_bucky_state
 	sta key_last_bucky_state
@@ -334,7 +338,7 @@ next_row:
 	;; so that RUN/STOP etc can be checked easily
 	;; (Compute's Mapping the 64, p27)
 	lda ScanResult+0
-	sta STKEY
+	sta STKEY ; XXX this variable should be set by UDTIM
 
 	;; Store de-bounce data for bucky keys
 	;; (Compute's Mapping the 64, p58-59)