Installation and Operation Manual
X-DPT-DeviceNet-SLA5800-SLAMf-Series-RevB-PC-eng
Part Number: 541B200AAG
March, 2015
101
Section 8 - Glossary
Brooks DeviceNet PCs
Explicit Connection
An Explicit Connection dictates a request and response exchange between
two devices. The device sending the request must get a response from the
device receiving the request message. Embedded in the Explicit Message is
information about the Class, Instance, Attribute, Service, and any service
data needed to process the message. As a result, processing of Explicit
Messages generally takes longer than I/O messaging. This is why Explicit
Connections are typically used for commissioning/configuration.
I/O Con
n
ection
I/O Connections are used for the exchange of data only. How a device
processes the data and/or responds with data via an I/O Connection is
defined within the Produce and Consume Path attributes of the I/O
Connection instance (See EPATH and Assembly above).
Instance
An instance of a Class is a particular invocation of a Class (sometimes
referred to as an Object). An Instance of a Class is unique in describing the
behavior for a particular kind of object. Each instance of the class contains
the same set of attributes defined by the class. The uniqueness of the
instance is defined by the attribute values.
Example:
Assume that a device contains two sensors, one to measure pressure, the
other to measure temperature. To access information about one or the other
sensor, two Instances of the class
S-Analog Sensor
class would need to
exist. Each sensor would have the same attribute set because they were
both created from the class S-Analog Sensor, but the values in each attribute
set would be unique to the sensor to describe pressure or to describe
temperature.
Example:
The class Connection contains information about configuring a Connection.
With most kinds of DeviceNet devices, multiple Connections are established
within a device to exchange information. In most cases one Explicit type
Connection is created to configure the device, another I/O type Connection is
created to transfer larger amounts of data. Each type of Connection is
created from the Connection class. Each Connection has unique information
in its Attribute set that defines the behavior of the Connection et. al. an
Explicit type Connection or an I/O type Connection.
