Node Guarding - Mitsubishi Electric MELSEC-F FX3U-CAN User Manual

FX -CAN User's Manual
3U
5.6.8

Node guarding

This protocol is used to detect remote errors in the network. Each NMT slave serves one requests message
for the node guarding protocol.
The NMT master polls each NMT guarding slave at regular time intervals. This time-interval is called the
guard time and may be different for each NMT slave. The response of the NMT slave contains the NMT state
of that NMT slave. The node lifetime is given by guard time multiplied by lifetime factor. The node lifetime may
be different for each NMT slave. If the NMT slave has not been polled during its lifetime, a remote node error
is indicated through the NMT service life guarding event. A remote node error is indicated through the NMT
service node guarding event if:
NMT master:
• The NMT master does not receive confirmation after the Guarding request within the node life time.
• The response of the NMT guarding slave state does not match the expected state.
NMT slave:
• The NMT guarding slave did not receive the NMT master Guarding request polling for time set in H100C
and H100D.
If a remote error occurred previously but the errors in the guarding protocol have disappeared, it will be
indicated that the remote error has been resolved through the NMT service node guarding event and the NMT
service life guarding event.
If Heartbeat is activated, the Node guarding settings will be ignored.
Note
• As Slave, the FX
Use the heartbeat service for FX
• Node guarding produces a high bus load. It is recommended to use heartbeat instead.
NMT Master
1. Slave Setting
1) Object H100C: Guard time
The 16bit guard time in units of ms is the time limit for which the response must be sent. The value 0
disables life guarding.
Applicable for FX
2) Object H100D: Life time factor
The 8bit life time factor value multiplied by the guard time gives the life time for which the NMT Master
has to send the guarding request. The value 0 disables life guarding.
Both Objects have to be set to activate Node guarding. The order in which Guard time and Life time factor
are set does not matter.
Applicable for FX
2. Master Setting
1) Object H1F81: NMT slave assignment
66
-CAN (firmware Ver. 1.10 or later) supports Node Guarding.
3U
-CAN not supporting Node Guarding.
3U
COB-ID = 1792 + Node-ID
Request
Confirmation
t
Request
Confirmation
t
s:
t:
-CAN firmware Ver. 1.10 or later.
3U
-CAN firmware Ver. 1.10 or later.
3U
s
s
NMT slave state
4 Stopped
5 Operational
127 Pre-Operational
Toggle Bit
5 Introduction of Functions
5.6 Communication Profile Area
NMT Slave
Indication
Response
Indication
Response
→ Refer to Subsection 5.8.7