8/17/2023 0 Comments Messages openThe data frame with an 11-bit identifier is also called "base frame format". Using a low code number for time critical functions ensures the lowest possible delay. In case of a transmission collision, the bus arbitration used in the CAN bus allows the frame with the smallest id to be transmitted first and without a delay. In CANopen the 11-bit id of a CAN-frame is known as communication object identifier, or COB-ID. An extension to the CAN bus standard (CAN 2.0 B) allows extended frame ids of 29 bits, but in practice CANopen networks big enough to need the extended id range are rarely seen. This limits the number of devices in a CANopen network to 127 (0 being reserved for broadcast). The CANopen standard divides the 11-bit CAN frame id into a 4-bit function code and 7-bit CANopen node ID. Ĭommunication Communication objects ĬAN bus, the data link layer of CANopen, can only transmit short packages consisting of an 11-bit id, a remote transmission request (RTR) bit and 0 to 8 bytes of data. There is an upcoming XML-style format, that is described in CiA 311. According to CiA 306, the format of the EDS-file is the INI file format. Given suitable tools, the content of the object dictionary of a device, based on an electronic data sheet (EDS), can be customized to a device configuration file (DCF) to integrate the device into a specific CANopen network. The first few entries in this area are as follows: The composite datatypes can be subindexed with an 8-bit index the value in subindex 0 of an array or record indicates the number of elements in the data structure, and is of type UNSIGNED8.įor example, the device communication parameters, standardized in the basic device profile CiA 301 are mapped in the index range 0x1000–0x1FFF ("communication profile area"). The basic datatypes for object dictionary values such as booleans, integers and floats are defined in the standard (their size in bits is optionally stored in the related type definition, index range 0x0001–0x001F), as well as composite datatypes such as strings, arrays and records (defined in index range 0x0040–0x025F).
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