Canopen Access Procedure; Introduction - Festo CiA 402 Manual

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CANopen access procedure

3 CANopen access procedure
3.1

Introduction

CANopen makes available a simple and standardised possibility to access the parameters of the motor
controller (e.g. the positioning speed). To achieve this, a unique number (index and subindex) is as-
signed to each parameter (CAN object). The totality of all adjustable parameters is designated an ob-
ject directory.
For access to the CAN objects through the CAN bus, there are fundamentally two methods available: A
confirmed access type, in which the motor controller acknowledges each parameter access (via so-
called SDOs), and an unconfirmed access type, in which no acknowledgement is made (via so-called
PDOs).
Order from the
controller
Controller
SDO
Confirmation from
the motor controller
Fig. 3.1 Access procedure
As a rule, the motor controller is parametrised via SDOs and controlled via PDOs. In addition, other
types of messages (so-called communication objects), which are sent either by the motor controller or
the higher-level controller, are defined for special application cases:
Festo – GDCP-CMMS/D-C-CO-EN – 1404NH – English
CMMS Controller
Controller
CMMS
PDO
(transmit PDO)
Data for the controller
(actual values)
CMMS
PDO
(receive PDO)
Data from the
controller (setpoint
values)
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