144
ifm
System Manual
ecomat
mobile
SmartController (CR2500) V05
CAN in the ecomatmobile controller
Summary CAN / CANopen
8.8
Summary CAN / CANopen
•
The COB ID of the network variables must differ from the CANopen Device ID in the controller
configuration and from the IDs of the functions CANx_TRANSMIT and CANx_RECEIVE!
•
If more than 8 bytes of network variables are put into one COB ID, CANopen automatically
expands the data packet to several successive COB IDs. This can lead to conflicts with manually
defined COB IDs!
•
Network variables cannot transport any string variables.
•
Network variables can be transported...
- if a variable becomes TRUE (Event),
- in case of data changes in the network variable or
- cyclically when the timer has elapsed.
•
The interval time is the period between transmissions if cyclical transmission has been selected.
The minimum distance is the waiting time between two transmissions, if the variable changes too
often.
•
To reduce the bus load, split the messages via network variables or CANx_TRANSMIT to several
plc cycles using several events.
•
Each call of CANx_TRANSMIT or CANx_RECEIVE generates a message packet of 8 bytes.
•
In the controller configuration the values for [Com Cycle Period] and [Sync. Window Length]
should be identical. These values must be higher than the plc cycle time.
•
If [Com Cycle Period] is selected for a slave, the slave searches for a Sync object of the master
during exactly this period. This is why the value for [Com Cycle Period] must be higher than the
[Master Synch Time].
•
We recommend to select "optional startup" for slaves and "automatic startup" for the network. This
reduces unnecessary bus load and allows a briefly lost slave to integrate into the network again.
•
Since we have no inhibit timer, we recommend to set analogue inputs to "synchronous
transmission" to avoid bus overload.
•
Binary inputs, especially the irregularly switching ones, should best be set to "asynchronous
transmission" using an event timer.
•
To be considered during the monitoring of the slave status:
- after the start of the slaves it takes a while until the slaves are operational.
- When the system is switched off, slaves can indicate an incorrect status change due to early
voltage loss.
