Sensors & Transducers e-Digest, Vol. 102, Issue 3, March 2009: Standardization
Nuremberg, 2009-03-10. - CAN in Automation (CiA) has released the CiA 302 specification series of CANopen additional functions. This set of specifications comprises descriptions of CANopen manager including Flying NMT (network management) master, SDO (service data object) manager, configuration manager, bus-line redundancy, and CANopen-to-CANopen gateways. The CiA 302 series version 4.1 substitutes the CiA 302 version 3.3 published 2003.
Part 1 contains some general definitions.
Part 2 defines in detail the NMT boot-up procedure and the flying NMT master concept. Flying NMT masters are required in mission- or safety-critical network applications, where single failure should not lead to a complete network shutdown. In case that the NMT master device fails, another NMT master capable device takes over. If the original NMT master device recovers from the failure situation, the actual redundant NMT master device gives the NMT master functions back to the original one.
Part 3 of CiA 302 specifies the program download and configuration manager. These additional functions are used in decentralized control systems, where one entity – the CANopen manager device – configures all devices after power-on. The software download is performed by means of segmented SDO communication.
In part 4, the use of network variables is described. Programmable devices have no pre-defined process data. For that reason, the object dictionary provides in the address range from A000h und AFFFh network variables.
Part 5 specifies the SDO manager, an additional CANopen function for NMT master devices. The SDO manager is necessary, if a simple CANopen device with just the SDO default server should be configured on-line by an external tool. In this case, the tool rents the correspondent SDO client from the NMT master device.
Part 6 defines bus-line redundancy as requested in marine and other mission-critical applications. There is a default bus-line and a redundant bus-line. If the default bus-line is corrupted, all connected devices will automatically switch to the redundant bus-line.
Part 7 describes the CANopen-to-CANopen router and bridge functions. The original request comes from companies that use cascaded CANopen networks. SDO and Emergency communication is routed, while PDOs (process data object) are forwarded with the bridge functionality. The SDO router function requires an additional SDO command, which is send before the normal or expedited SDO. With the additional CANopen functions defined in the CiA 302 specification set, the CANopen users can design very complex and sophisticated network systems also for mission-critical applications. Some of these additional functions are required in rail-vehicles, an application domain where CANopen gains increasingly importance. Another new application field is battery-powered service robots.
CAN in Automation (CiA) GmbH
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