CAN-8123/CAN-8223/CAN-8423 user’s manual (Revision 3.00, May/22/2009) ------
46
Node Guarding Protocol
The Node Guarding Protocol follows the Master/Slave relationship. It
helps users monitoring the node in the CAN bus. The communication method
of node guarding protocol is defined as follows.
Slave state
Slave state
NMT Master
NMT Slave
request
request
confirm
confirm
indication
indication
indication
indication
Node Guarding Event
Life Guarding Event
Node
Guard
Time
Node
Life
Time
Guarding error
Remote transmit request
Remote transmit request
response
response
The NMT master will inspect each NMT slave at regular time intervals.
This time-interval is called the node guard time, given by the “guard time * life
time factor”, and may be different from each NMT slave. And the response of
the NMT slave contains the state of that NMT slave, which may be in a
"
Stopped
", "
Operational
", or "
Pre-operational
" state. The node life time
factor can also be different for each NMT slave. If the NMT slave has not been
inspected during its life time, a remote node error will be given, and indicate
through the "Life Guarding Event" service.
In addition, the reported NMT slave state, which does not match the
expected state, will also produce the “Node Guarding Event”. This event may
occur in the DO and AO channels, and output the error mode value, recorded
in the object with index 0x6207 and index 0x6444. Moreover, the object with
index 0x6206 and 0x6443 can control the error mode value of the DO or AO
channels in enabling or disabling when the “Lift Guarding Event” has been
indicated. For more information about objects with index 0x6206, 0x6207,
0x6443, and 0x6444, please refers to the chapter 6.
