CANopen gateway
Wieland Electric GmbH | BA000970 | 11/2016 (Rev. F)
Guarding protocols
910844299
CANopen offers several possibilities for active monitoring of the correct function
of the field bus interface (e.g. cable break detection).
ATTENTION
Always use either node guarding or heartbeat!
Guarding is compulsory according to the CIA CANopen specifications DS 301. Please always
active either node guarding or heartbeat. When no guarding has been configured, the sa-
mosPRO system cannot detect an interruption of the CANopen communication, for example
an interrupted network cable. In this case the input and output data of the CANopen gateway
may "freeze".
Heartbeat
A heartbeat producer is a CANopen device that sends a cyclic heartbeat message. This makes
it possible for all other CANopen devices to detect whether the heartbeat producer still func-
tions correctly and what its current status is. Heartbeat messages are transmitted at regular in-
tervals, the Producer Heartbeat
Time, which may be configured with the aid of SDO 1017. The configured 16-bit value
is rounded up to the next higher multiple of 4 ms.
A heartbeat consumer is a CANopen device that expects a cyclic node guarding message
within a certain time interval, i.e. the consumer heartbeat time, which can be configured with
the aid of SDO 1016. If the heartbeat consumer does not receive a node guarding message
within the configured consumer heartbeat time, it sends a life guarding emergency message
and sets the process input data to 0. In addition, the gateway sends a "cable break" error mes-
sage that can be processed by the controller module.
Node guarding
Node guarding is carried out by a NMT master. This can be any CANopen device that can fulfill
this function as a client. The NMT master sends a cyclic node guarding message to the device
to be monitored, which must respond within a certain time, which is monitored by the NMT
master. If the device to be monitored does not respond within the node guarding time, the
NMT master treats this as a malfunction of the device and takes the corresponding actions.
Life Guarding
Life guarding is carried out by the gateway itself. In the gateway, the life guarding time is cal-
culated from the values of SDO 100C (guard time) and SDO 100D (life time factor). If the gate-
way does not receive a node guarding message from an NMT master once within this life gua-
rding time, the gateway sends an internal "cable break" error message, which can be proces-
sed by the controller module, and the LED NS starts to flash red.
• The gateway can detect a cable break when life guarding has been activated, i.e. when
both SDO 100C and SDO 100D have a value not equal to 0. In this case, Life Guarding
starts as soon as the first Node Guarding request is received from an NMT master and
ends when the master sends the “Reset Communication” command.
• Alternatively cable break detection is possible when the gateway has been configured as
a heartbeat consumer. In this case the cable break detection is carried out by the gate-
way itself.
• Heartbeat (producer) works without node guarding. In this case gateway cannot detect a
cable break on the field bus.
• Heartbeat and node guarding / life guarding cannot be simultaneously used.
• If the configuration has been changed in such a way that life guarding is deactivated or
activated, the entire samosPRO system must be restarted, so that the CANopen network
communication can again be correctly established.
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