Bitfield('flag', 1,
                 Bitfield.Bit('receive_message_available', 1, 0),
                 Bitfield.Bit('event_message_buffer_full', 1, 0),
                 Bitfield.ReservedBit(1, 0),
                 Bitfield.Bit('watchdog_pretimeout_interrupt_occurred', 1, 0),