Error Control - Node Guarding - WEG SSW900-CAN-W User Manual

for operation. In the operational state all the objects are available, whereas in the stopped state only the NMT object
can receive or transmit telegrams to the network. The next table shows the objects available for each state.
This state machine is controlled by the network master, which sends to each slave the commands so that the desired
state change be executed. These telegrams do not have confirmation, what means that the slave does only receive
the telegram without returning an answer to the master. The received telegrams have the following structure:
1 = START node (transition 3)
2 = STOP node (transition 4)
128 = Enter preoperational (transition 5)
129 = Reset node (transition 6)
130 = Reset comunication (transition 7)
The transitions indicated in the command code correspond to the state transitions executed by the node after
receiving the command (according to the figure 8.4). The Reset node command makes the slave execute a complete
reset of the device, while the Reset communication command causes the device to reinitialize only the objects
pertinent to the CANopen communication.

8.5.2 Error Control - Node Guarding

This service is used to make it possible the monitoring of the communication with the CANopen network, both by
the master and the slave as well. In this type of service the master sends periodical telegrams to the slave, which
responds to the received telegram. If some error that interrupts the communication occurs, it will be possible to
identify this error, because the master as well as the slave will be notified by the Timeout in the execution of this
service. The error events are called Node Guarding for the master and Life Guarding for the slave.
Table 8.11: Objects accessible in each state
Initialization Préoperational
PDO
SDO
SYNC
EMCY
Boot-up •
NMT
Identifier byte 1
00h Command Code
Table 8.12: Commands for the state transition
Command Code
COMMUNICATION OBJECTS DESCRIPTION
Operational Stopped
•
• •
• •
• •
• •
byte 2
Destination Node-ID
Destination Node ID
0 = All the slaves
1 ... 127 = Specific slave
•
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