CANopen gateway
Wieland Electric GmbH | BA000970 | 07/2019 [9855]
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Guarding protocols
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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 samosPRO system
cannot detect an interruption of the CANopen communication, for example an interrupted net-
work 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 pos-
sible for all other CANopen devices to detect whether the heartbeat producer still functions cor-
rectly and what its current status is. Heartbeat messages are transmitted at regular intervals, 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 message 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 mo-
nitored, which must respond within a certain time, which is monitored by the NMT master. If the de-
vice 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 calculated
from the values of SDO 100C (guard time) and SDO 100D (life time factor). If the gateway does not
receive a node guarding message from an NMT master once within this life guarding time, the gate-
way sends an internal "cable break" error message, which can be processed by the controller modu-
le, and the LED NS starts to flash red.
NOTICE
• 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 gateway 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 acti-
vated, the entire samosPRO system must be restarted, so that the CANopen network commu-
nication can again be correctly established.
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