Ascon tecnologic CU-02, Руководство пользователя

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Chapter 4 - Programming the CPU
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4-6 CANopen Extension for Ascon sigma due CPU
4-6-1 Introduction
sigma due is a system based on two main concepts: the CANopen technology and
the IEC61131 standard languages. The integration of these two different worlds is
performed by:
• Use of networked variables;
• Direct access to CANopen parameters and functions via predefined low level
communication function blocks. CANopen services for CPU programs according
to the IEC61131-3 standard are defined in the CiA (CAN in Automation e.V.)
Draft Standard 405;
• Use of Ascon IO Library.
Using
Networked
Variables
Networked variables are the easiest way of data exchange in a CANopen network
system. Within the CPU, program access to the network variables occurs in the
same way as access to internal, local variables on the CPU. From the point of view
of a CPU programmer it is unimportant whether a input variable is assigned to a
local input on the CPU device or to an input on a networked expansion device. The
use of networked variables only requires basic knowledge of CANopen. In general,
a CANopen configuration tool as well as the availability of EDS files for the individ-
ual CANopen devices are required for integrating network variables into a CPU.
With the help of network variables it is possible:
• to expand the number of inputs and outputs on the PLC using distributed
CANopen I/O devices;
• to exchange process data between various control units, thus realizing decen-
tralized automation control projects;
• to integrate other special CANopen devices from third party vendors into a
complex control project and furthermore to build very specific automation con-
trol systems using modular components in addition to Ascon
sigma due CAN-
open IO modules.
For a detailed description see [3]
and
[4] .
Using
CANopen
Function blocks
CANopen function blocks enable direct access to specific CANopen services, thus
offering a high degree of flexibility in the target application. Furthermore, using
these function blocks does not require an additional CANopen configuration tool or
EDS files. However, using the CANopen function blocks assumes that the user
has detailed knowledge about CANopen and its services.
With the help of CANopen function blocks it is possible:
• to directly exchange data with other CANopen nodes via SDO (Service Data
Object) or PDO (Process Data Object);
• to enquire and change the state of other CANopen nodes;
• to receive error messages from other CANopen nodes;
• to allow generation of SYNC messages.
For a detailed description see [3]
and
[4] .
Using
Ascon I/O
Library
The function blocks present in the Ascon IO Library enable the access to Ascon
sigma due CANopen IO modules, providing services that allow the CPU program-
mer to do not deal with the fieldbus directly. To provide this level of abstraction,
the function blocks are based on those described above.
With the help of the function blocks present in the library is possible:
• to directly exchange data with all sigma due CANopen module;
• to setup all the module’s functionalities;
• to enquire and see the state of the modules;
• to reset the module.
For a detailed description see [11]
and
[12]
.