GE LM10, Instruction Manual

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A–4 LM10 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
DEVICENET OVERVIEW CHAPTER A:
A.1.8 DeviceNet Specification Highlights
Description:
The DeviceNet specification defines a network communication system for transferring
data between elements of an industrial control and automation system. The specification
is divided into two volumes and defines the following elements:
Volume 1:
• DeviceNet communication protocol and application (Layer 7: Application layer)
• CAN and its use in DeviceNet (Layer 2: Data Link Layer)
• DeviceNet physical layer and media (Layer 1: Physical Layer)
• Volume 2:
• Device profiles for interoperability and interchangeability among like products
CAN defines the syntax or form of the data transfer. The DeviceNet application layer
defines the semantics or meaning of the data transferred
Communication Protocol and Application:
Standard or application specific objects are combined together into Device Profiles by the
applications using DeviceNet. The Device Profile defines the device as viewed from the
network: DeviceNet specifications contains a library of objects and Device Profiles. ODVA
coordinates the work of industry experts in the development of both new Object and
Device Profile specifications.
DeviceNet supports strobed, polled, cyclic, change-of-state, and application-triggered
data transfer. The user can choose master/ slave, multi-master and peer-to-peer, or a
combination depending on device capability and application requirements. The choice of
data transfer can significantly speed up system response time. One popular application for
DeviceNet is to use a standard, predefined set of connections that allow devices to
operate in a master/slave connection set.
Connections:
The DeviceNet communication protocol is based on the idea of connections. Connections
must be established with a device in order to exchange information with that device.
Table A–1: Trunk Cable Length Specification
Baud rate 100% thick cable 100% thin cable Flat cable
125 kbps 500 meters 100 meters 420 meters
250 kbps 250 meters 100 meters 200 meters
500 kbps 100 meters 100 meters 100 meters
Table A–2: Drop Cable Length Specification
Baud rate Maximum Cumulative
125 kbps 6 meters 156 meters
250 kbps 6 meters 78 meters
500 kbps 6 meters 39 meters