+extern char _nvram[]; /* 2048 bytes of nvram! */
+// uncomment for testing. char _nvram[20]; /* 2048 bytes of nvram! */
+/* NVRAM map:
+ *
+ * START LEN
+ * 0x800 0x02 mic.h - current challenge
+ * 0x802 0x10 mic.h - current secret password
+ * 0x812
+ *
+ */