User Manual for ELD2-CAN Servo
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two different values due to a toggle bit in the returned value. If there is no response, or an unacceptable state
occurs, the NMT master could report an error to its host application.
The NMT master sends a node guarding request using the following a Remote Frame message:
COB-ID(hex)
Number of Bytes
RTR
0x700+Node-ID
0
1
The NMT slave will generate a node guarding answer using the following message:
COB-ID(hex)
Number of Bytes
RTR
Data field(Byte 1)
Bit 7
Bit 6 to 0
0x700+Node-ID
1
1
Toggle
NMT communication state
Note that the slave answers toggling a bit between consecutive responses. The value of the toggle bit of the
first response after the guarding protocol becomes actives is zero.
The state of the heartbeat producer could be one of the followings:
Communication State value(hex)
State definition
00
Boot-up
04
Stopped
05
Operational
7F
Pre-operational
Example of NMT Node guarding:
COB-ID(hex) Number of Bytes
Data(hex)
Description
701
0
-
Master sends a CAN remote frame without data to node 1
701
1
7F
Node 1 sends the actual NMT state (pre-operational)
toggling the 7
th
bit
701
0
0
Master sends a CAN remote frame without data to node 1
701
1
FF
Node 1 sends the actual NMT state (pre-operational)
toggling the 7
th
bit
Protocol heartbeat
The heartbeat protocol defines an error control service without need for remote frame. A heartbeat producer (in
this scope a controller) transmits a Heartbeat message cyclically. Transmit cycle of heartbeat message could be
configured using the object Producer heartbeat time (0x1017). If the Heartbeat is not received by the consumer
(in this scope a master) within an expected period of time (normally specified as Consumer heartbeat time)
It could report an error to its host application.
The heartbeat message generated by the producer will be as follows:
COB-ID(hex)
Number of Bytes
Data field(Byte 1)
Bit 7
Bit 6 to 0
0x700+Node-ID
1
Reserved
NMT communication state
The state of the heartbeat producer could be one of the followings:
Communication State value(hex)
State definition
00
Boot-up
04
Stopped
05
Operational
7F
Pre-operational