Various CANopen performances are detailed below.
Impact on Task Cycle Time
The time given to each task cycle is as follows:
|
Task
|
Typical
|
|
CANopen inputs
|
10 μs / PDO
|
|
CANopen outputs
|
80 μs + 15 μs / PDO
|
|
Diagnostics
|
120 μs
|
The following figure gives an overview of the SDO management:
The following table defines the terms that are used to describes the ‘Communication by SDO’ graphic:
|
Term
|
Definition
|
|
Tcycle
|
User task cycle
|
|
n
|
Number of SDO to execute in parallel
|
|
Tsdo
|
Time to process the n SDOs (multiple of 5 ms due to the polling task)
|
|
Average time
|
Average time to execute all the SDO from SDO1 to SDOn.
The average time depends on the Tcycle, n and Tsdo:
|
NOTE: A polling task runs every 5 ms and at each task cycle in order to check the end of the exchange.This is useful if the user runs many SDOs.
Example: for a task cycle of 50 ms, a number of 10 SDOs/Mast Cycle and a SDO exchange time of 3 ms.
With the polling task, you can treat 2 SDOs/5ms. In order to do that, these SDOs must be addressed to two different devices.
Therefore, we can launch 10 SDOs/task cycle.
The CANopen bus start time depends on the number of devices.
The minimum time to start a CANopen bus is 7 seconds.
The time to configure one device is about 0.8 second.
The start time of a CANopen bus with 64 devices is about 1 minute.
Disconnection/Reconnection of a Device
Disconnection:
The time to detect the disconnection of a device depends on the error control:
|
Error control
|
Description
|
|
Guardtime
|
The time to detect the disconnection is Guardtime * life time factor
|
|
Heartbeat
|
The time to detect the disconnection is Heartbeat producer time + (Heartbeat producer time /2)
|
Reconnection:
Each second, the master polls on the device to check the reconnection of the device. The time to reconnect the device is about 1 second if the device is not alone on the bus.
If the device is alone on the bus, the disconnection of the device set the master in the same case as the disconnection of the complete bus. After this state, the master restarts the bus and the reconnection time of the device is about 7 seconds.
