add msbasic

msbasic/kilian_extra.s

@@ -0,0 +1,28 @@
+.segment "EXTRA"
+.export MONRDKEY, MONCOUT, LOAD; SAVE; ISCNTC
+
+LOAD:
+        rts
+
+SAVE:
+        rts
+
+ISCNTC:
+        rts
+
+MONRDKEY:
+        lda $BC01
+        bmi MONRDKEY_SKIP_ECHO
+        sta $BC00       ; echo
+MONRDKEY_SKIP_ECHO:
+        rts
+
+MONCOUT:
+        sta $BC00
+
+        rts
+
+.segment "RESETVEC"
+        .word   $0000           ; NMI vector
+        .word   COLD_START      ; RESET vector
+        .word   $0000           ; IRQ vector