Rockwell Automation VSM500 Integrated Drive/Motor DeviceNet Option Board - Manual (Page 93)

Glossary D-1
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PPENDIX
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Glossary
Assembly Objects: The DeviceNet Specification defines Assembly Objects as
objects that “bind attributes of multiple objects to allow data to or from each object to
be sent over a single connection.” The VSM500 unit with a DeviceNet option board
uses assembly objects to transmit data to and from a scanner over a control I/O
connection. The terms “input” and “output” are defined from the scanner’s point of
view. Output assemblies are sent by the scanner and consumed by the unit. Input
assemblies are sent by the unit and consumed by the scanner.
Bus Off: A bus off condition occurs when an abnormal rate of errors is detected on
the Control Area Network (CAN) bus in a device. The bus-off device cannot receive or
transmit messages on the network. This condition is often caused by corruption of the
network data signals due to noise or data rate mismatch.
Change of State (COS) I/O Data Exchange: A device that is configured for change of
state I/O data exchange transmits data only when its data has changed. This type of
exchange can reduce network traffic and save resources since old data does not need
to be transmitted or processed.
Classes: A device has many objects. Each type of object is grouped in a class that is
identified with a unique ID number.
Controller: A controller, also called programmable logic controller and processor, is a
solid-state control system that has a user-programmable memory for storage of
instructions to implement specific functions such as I/O control, logic, timing, counting,
report generation, communication, arithmetic, and data file manipulation. A controller
consists of a central processor, input/output interface, and memory. See also Scanner.
Cyclic I/O Data Exchange: A device configured for cyclic I/O data exchange
transmits data at a user-configured rate. This type of exchange ensures that data is
updated at an appropriate rate for the application, preserves bandwidth for
rapidly-changing devices, and allows data to be sampled at precise intervals for better
determinism.
Data Rate: The data rate, sometimes called baud rate, is the speed at which data is
transferred on the DeviceNet network. The available data rates depend on the type of
cable and total cable length used on the network:
Each device on a DeviceNet network must be set for the same data rate. You can set
the DeviceNet option board to 125K, 250K, or 500K. You can set it to Autobaud if
another device on the network has set the data rate.
Maximum Cable Length Based on Data Rate
Cable 125 K 250 K 500 K
Thick Trunk Line 500 m (1,640 ft.) 250 m (820 ft.) 100 m (328 ft.)
Thin Trunk Line 100 m (328 ft.) 100 m (328 ft.) 100 m (328 ft.)
Maximum Drop Length 6 m (20 ft.) 6 m (20 ft.) 6 m (20 ft.)
Cumulative Drop Length 156 m (512 ft.) 78 m (256 ft.) 39 m (128 ft.)