D.8.7 Node Monitoring (Node Guarding)/(Error Control Message) - Festo EMCA-EC-67 Series Translation Of The Original Instructions

D CANopen communication
D.8.7 Node monitoring (Node guarding)/(Error control message)
Overview
The Node guarding protocol can be used to monitor communication between slave (e.g. EMCA) and
master (e.g. higher-order controller). With the Node guarding protocol, master and slave monitor each
other: The master queries the EMCA cyclically about its NMT status. In every response of the EMCA, the
Toggle-Bit (bit 7) is inverted (toggled). If these responses are not made or the EMCA always responds
with the same toggle bit, the master can react correspondingly. Likewise, the EMCA monitors the regu­
lar arrival of the master's node guarding requests. If the message is not sent within the parameterised
cyclical monitoring time (Life time) è page 267, the EMCA triggers the error "CAN Node Guarding, FB
has master control" (FCT code: 1Ch).
Interruption of the CAN bus connection (e.g. wire break) can be reliably detected only
through the Node guarding. The Node guarding is active when Guard time (100C
Life time factor (100D
Node guarding messages:
The master's request must be answered as a remote frame with the CAN-ID "700h + node ID". In the
remote frame, the RTR bit is also set in the message (= 1). Remote frames have no data.
CAN-ID: 700h + node ID (example: node ID = 1)
701
h
Fig. D.17 Structure: Node guarding with remote bit
The response of the EMCA is structured as follows. It contains only 1 byte of user data, the toggle bit
and the NMT status of the EMCA è chapter D.8. In the remote frame, the RTR bit is also not set in the
message (= 0).
CAN-ID: 700h + node ID (example: node ID = 1)
701 1
h
Data length
Fig. D.18 Structure: Node guarding with toggle bit
266
) are > 0.
h
1st data byte: toggle bit/NMT status
T/N
Festo – GDCE-EMCA-EC-C-HP-EN – 1611b – English
) and
h