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Chapter 4. Data Communication Protocol of the CANopen
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4.3.1 Protocol node guarding
Master inquires the Slave for normal operation via the RTR Frame, and the
Slave returns the current NMT State to the Master.
The NMT status of the Slave is indicated by the value of S;
-. 4: Stopped
-. 5: Operational
-. 127: Pre-operational
The ’t’ of the top bit is the Toggle Bit which toggles at every response of the
Slave.
The Master sends the RTR Frame at every preset Node guard time. If the
Master fails to send RTR Frame until the expiration of the Node life time, or
the Slave fails to response to the Mater until the expiration of the Node life
time, a Guard Error is generated. Then, the Guard Error Event set up in
each Master and Slave is executed. In the case of iG5A, the CANopen
NMT State is changed to Pre-operational.
4.3.2 Protocol heartbeat
If the Error Control Protocol is set to Heartbeat, the MNT State
information of itself is sent at the time intervals set up in the Heartbeat
Producer. If the Heartbeat Producer fails to send the Heartbeat within the
preset time, the Heartbeat consumer generates a Heartbeat event.