Devices related to the CANopen bus protocol

We have previously introduced the basic concepts of the CANopen bus protocol. Now we will take a look at the CANopen bus protocol equipment. First, let's take a look at the features of these devices through the following aspects. We will also know why CANopen bus is becoming increasingly popular in the market.

Object Directory)

The object dictionary is the central element of each CANopen bus protocol device. It describes all the functions of devices on the network. The object dictionary describes the interfaces between networks and applications. All object dictionary entries reference 16-bit indexes and 8-seat indexes. The object dictionary contains all network access parameters, such as device identifiers, producer names, PDOs and SDOs communication parameters, and device monitoring error control ") are stored in the common area of the object dictionary. The device description area includes input and output of the I/O function switch and analog quantity), device parameters, and PLC ing. If an error occurs, you can configure the behavior of the object dictionary. Therefore, the object dictionary can adapt device behavior to their respective applications.

Device description

The device description table describes the attributes and features of the main device types in the automatic control system. Defines the features and parameters of the standard device type. All parameters are saved in the object dictionary. This ensures that CANbus accesses the CANopen bus protocol device in the same way. The interoperability and interchangeable nature of devices of different manufacturers provide preconditions for a wide range of customers. For switch and analog I/O devices, a device description table is defined for PLC devices and controllers. The parameters and properties of the CANopen bus protocol device are described in ASCII format in the standard EDS file. It accesses the network as a table containing all device properties. DCFdevice configuration file exists in the real-name insured instance configured by the dedicated device). DCF inherits from EDS.

Use PDO/SDO for data transmission

CANopen bus protocol Data transmission includes two different Data transmission mechanisms, CANopen is a Process Data Object PDOs, Process Data Object) to Process short Process Data fast exchange. Through SDOService Data Object) to access the Object dictionary entry. PDO is transmitted cyclically or query based on event constraints. Its transmission is in the form of no protocol broadcast. One PDO can be transmitted in eight bytes, and one synchronization information is synchronized to the transmission and migration of data on the network. The attributes of each pdo can be configured in the object dictionary, including the communication parameter CAN identifier, transmission type, and so on) and process data is allocated for each PDO ing. SDO verifies data transmission through two CAN-telegrams and establishes point-to-point communication between the two devices. In this way, large data packets larger than 8 bytes can be transmitted to each SDO.

Network Management

Network Management (NMT) is used to manage the status of network devices. It is a structure of the master-slave relationship. The CANopen device sends a signal to the NMT master through a startup packet, Which is initialized and activated on the network. The NMT command can be used to change the status of a single device or the entire network device. The status of each device is determined by a specific attribute. PDO can be transmitted only in the OPERATIONAL status; configure the device under the PRE_OPERATIONAL condition. To monitor the Communication Status of CANopen Bus Protocol devices, you can select Node-Guarding or Heartbeat to define alarm messages for reporting device errors. These emergency messages are event-oriented; when an error occurs, the standard error code details the error message.

CANopen Safety

CANopen bus integrates security functions such as Emergency OFF and Two-handed operation to transmit information securely. The dedicated safety-relevant servicesSRDO, Safety Relevant Data Object) receives communication, and an SRDO transmits up to 8 bytes of security information, which is completed in a defined time window.

Introduction to CANopen bus protocol

CiA DS 301: CANopen application layer and communication description

CiA DS 304: Communication racks related to CANopen Security

CiA DS 401: Device description of the CANopen local I/O module

CiA DS 404: CANopen detection device and Closed-Loop Controller Device description

CiA DS 405: CANopen complies with the device and interface descriptions of IEC61131-3-ready Programmable Devices

CiA DS 406: CANopen encoder device description

DS301: defines the application layer and communication specifications, including object dictionaries, service data objects, process data objects, and network management objects.

DS302: defines the network startup steps, the definitions of the master and management nodes, the input/output definitions of programmable devices, and the redundant communication methods.

DS305: awaiting Query

DS401: defines the device specification of the general I/O module, mainly defines the content between 6000H and 6FFFFH in the object dictionary.

DS402: defines the device specification for motion control.

DS405: defines the standard device specification of IEC61131, mainly defines the content between A000H and A6FFH.

DS401, DS402, and DS405 all provide default ing data.