Hardware manual

RX600 Series CAN Application Programming Interface
R01AN0339EU0203 Rev. 2.03 Page 26 of 29
Mar 23, 2013
Figure 6. CAN Internal Loopback mode.
This lets you test the functionality of a node without having a CAN bus connected.
Internal Loopback can be convenient when testing as this mode allows the CAN controller to run without sending CAN
errors due to no Acks received when the node is alone on the bus, it acknowledges transmitted frames itself.
10.2 External Loopback - Test Lone Node On Bus
External Loopback is like Internal Loopback with the only difference that there must be a CAN bus connected to the
node. The messages are acknowledged by the node so the node can be alone on the bus. This is an advantage as nodes
can be tested standalone.
Figure 7. External Loopback. The message is transmitted onto the CAN bus and can be received
back on the same node. This is convenient when testing code and when a node is alone on the bus.
10.3 Listen Only (Bus Monitoring) - Test a Node Without Affecting Bus
In Listen Only, or Bus Monitoring, the node is quiet. A node in Listen Only mode will not acknowledge messages or
send Error frames etc.
Caution: Mark entering listen only mode clearly in your code so you remember to disable Listen Only mode again! If
you only have two nodes on the network and one of them goes into Listen Only, the other node will not get any Acks
and will eventually go Bus Off. Also, don’t request any transmissions in Listen Only as that is not a correct behavior
and the CAN module has not been designed for this.