User Manual of iSV2-CAN Servo
www.leadshine.com
57
Example of NMT heartbeat:
COB-ID(hex) Number of Bytes
Data(hex)
Description
705
1
7F
Node 5 sends a heartbeat indicating pre-operational state
705
1
7F
After producer heartbeat time, Node 5 sends again a
heartbeat indicating pre-operational state
Protocol life guarding
In Life guarding protocol the NMT slave monitors the status of the NMT master. This protocol utilizes the
objects Guard time (0x100C) and Life time factor (0x100D) to determine a "Lifetime" for each NMT slave
(Lifetime = Guard Time * Life Time Factor). If a node does not receive a Node Guard message within its
Lifetime, the node assumes communication with the host is lost sends an emergency message and performs a
fault reaction. Each node may have a different Lifetime.
Example of NMT life guarding:
COB-ID(hex)
Number of
Bytes
RTR
Data(hex)
Description
705
1
1
-
Master sends a CAN remote frame without data
to node 1
705
1
1
-
Master sends a CAN remote frame without data
to node 1
…
…
…
…
Delay Higher than Guard Time*Life Time Factor
81
8
0
30 81 11 00
00 00 00 00
Node 1 send an EMCY indicating the lifeguard
error
Protocol boot-up
An NMT slave issues the Boot-up message to indicate to the NMT-Master that it has entered the state
Pre-operational from state Inititalising
Example of NMT Boot-up:
COB-ID(hex) Number of Bytes
Data(hex)
Description
705
1
00
Node 5 sends a boot-up NMT message
5.4 SDO
The SDO are communication channels with two basic characteristics:
⚫
Client / Server relationship
⚫
It provides access to the dictionary of CANopen objects of the device.
The SDO are used to transfer multiple object content simultaneously (each with an arbitrary amount of
information) from client to server and vice versa.
SDO are transferred as a sequence of segments. Before sending the segments there is an initialization process
in which the server and clients prepare themselves to send the segments. However, it is also possible to send
information (up to 4bytes) during the initialization process. This mechanism is called SDO expedited transfer.
The SDO message will be as follows: