To finish off, there are several test modes available that may be useful, for example, during product development. There are two Loopback modes called Self Test Mode 1 and 2, and also a Listen only Mode. With Self Test Mode 1, the node can acknowledge its own data, and also store its own transmitted messages into a receive mailbox. This is normally not possible. The message is in other words transmitted via the CAN bus back to the same node. This can be convenient when testing code and when it is the only node on the bus. There needs to be a bus, but the node can be the only one on the bus.