#define RXBEID0_OFF 4
#define RXBDLC_OFF 5
#define RXBDAT_OFF 6
-#define RXFSIDH(n) ((n) * 4)
-#define RXFSIDL(n) ((n) * 4 + 1)
-#define RXFEID8(n) ((n) * 4 + 2)
-#define RXFEID0(n) ((n) * 4 + 3)
+#define RXFSID(n) ((n < 3) ? 0 : 4)
+#define RXFSIDH(n) ((n) * 4 + RXFSID(n))
+#define RXFSIDL(n) ((n) * 4 + 1 + RXFSID(n))
+#define RXFEID8(n) ((n) * 4 + 2 + RXFSID(n))
+#define RXFEID0(n) ((n) * 4 + 3 + RXFSID(n))
#define RXMSIDH(n) ((n) * 4 + 0x20)
#define RXMSIDL(n) ((n) * 4 + 0x21)
#define RXMEID8(n) ((n) * 4 + 0x22)