Mitsubishi Electric FX3U-CAN, User Manual

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5 Introduction of Functions
5.6 Communication Profile Area
66
FX
3U
-CAN User's Manual
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
3U
-CAN (firmware Ver. 1.10 or later) supports Node Guarding.
Use the heartbeat service for FX
3U
-CAN not supporting Node Guarding.
• Node guarding produces a high bus load. It is recommended to use heartbeat instead.
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
3U
-CAN firmware Ver. 1.10 or later.
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
3U
-CAN firmware Ver. 1.10 or later.
2. Master Setting
1) Object H1F81: NMT slave assignment
→ Refer to Subsection 5.8.7
NMT Master
Request
H100C : Guard time
H100D : Life time factor
H1F81 : Retry factor
Indication
Indication
Response
Response
Confirmation
Confirmation
Request
NMT Slave
COB-ID = 1792 + Node-ID
t s
s: NMT slave state
t: Toggle Bit
4 Stopped
5 Operational
127 Pre-Operational
s t
H1F81
: Guard time