Emerson SI-DeviceNet, User Manual

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SI-DeviceNet User Guide
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Issue Number: 2
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13 Glossary Of Terms
Address: This is the unique network identification given to a networked device to allow
communication on a network. When a device sends or receives data the address is
used to determine the source and the destination of the message.
Alignment: By default SI-DeviceNet transmits values as 32 bits on the network. It is
possible by using alignment to reduce the number of bits transmitted when sending 16-
bit (or smaller) values on the network to 16-bit (32-bit values will still be transmitted as
32-bit values). This has the advantage of reducing the volume of traffic on the network
and allowing more parameters to be mapped within SI-DeviceNet.
Bit: A binary digit, this may have the value of 1 or 0.
Byte: A collection of 8 binary digits that collectively store a value. This may be signed or
unsigned.
CAN: The base network used for DeviceNet. The DeviceNet module does not support
CAN commands.
DeviceNet: Builds on the basic CAN protocol by offering higher level functionality.
Casting: The process of changing between data sizes without changing the value
represented, e.g. changing from 16-bit to 32-bit.
Consistency: Describes how data is transmitted between nodes on the network. If data
is consistent it is transmitted from node to node as a single entity. Thus preventing data
corruption where multiple bytes are transmitted or received individually.
Control word: A collection of binary digits that are used to control the drive. Features
typically include directional controls, run controls and other similar functions.
Cyclic data: This consists of values that are sent at regular or cyclic intervals across the
network. A typical use of cyclic data would be the transmission of a speed reference or a
control word.
Data format: Determines the quantity and function of the data sent and received across
the network.
Data rate: Determines the communication speed of the network, the higher the value
the more data can be sent across the network in the same time period.
Device: A piece of equipment connected to a network, this may be any type of
equipment including repeaters, hubs, masters or slaves.
Double word: A 32-bit word, this may be signed or unsigned.
Earthing/Grounding: Describes the electrical safety or shielding connections for the
module.