STOP + RESTORE now works (bad news: works even without STOP)

c64/kernal/interrupts/fe47.default_nmi_handler.s

@@ -1,12 +1,25 @@
 
 default_nmi_handler:
 
-	;; XXX implement according to Compute's Mapping the Commodore 64, page 74
+	;; Implemented according to Compute's Mapping the Commodore 64, page 74
+	;; and to https://www.c64-wiki.com/wiki/Interrupt
+
+	;; Save registers, sequence according to Compute's Mapping the Commodore 64, page 73
+	pha
+	txa
+	pha
+	tya
+	pha
+
+	;; XXX: RS-232 support is not implemented
 
-	;; XXX check if the source was RESTORE key, quit if it wasn't (no RS-232 support)
 	;; XXX if cartridge present, enter it through warm start vector
-	;; XXX if stop pressed, go to default_brk_handler
 
-	inc $D020
-	rti
+	;; According to C64 Wiki, if STOP key is pressed, the routine assumes warm start request
+
+	jsr JSTOP
+	bcs +
+	jmp return_from_interrupt ; no STOP pressed
+*
+	jmp (CBINV) ; STOP + RESTORE