CDN36X User Manual
revision 1.30
DeviceNet Object Model
The DeviceNet Specification defines an Object Model that consists of Objects and Attributes.
An Object is a predefined software process, and an Object Attribute is a data value used or
created by that process. An Object can have multiple Instances, or the same process operating
with different sets of Attributes or data values. For the purpose of this document, an Object
Instance is an independent program or process, and its Attributes are configuration parameters
and data values that are unique to that specific Object Instance.
The CDN36X gateway has eight different Object Classes, or types. Five are standard objects
defined by the DeviceNet Specification (
Identity, Router, DeviceNet, Assembly, Connection
).
Three are specific objects defines for the CDN36X gateway (
Serial Stream, Serial Receive,
Serial Transmit
). The
Serial Stream Object
configures the serial channel, and scans the incoming
serial stream for valid message packets. The
Serial Receive Object
processes the received
message packet, converts it into input data, and returns it to the DeviceNet master. The
Serial
Transmit
Object
receives output data from the DeviceNet master, converts it into a message
packet, and transmits it out the serial channel. You can configure up to 8 Instances each for the
Serial
Receive
Object
and
Serial
Transmit
Object
. Chapter 5 contains detailed information on
each DeviceNet object class.
DeviceNet Interface
The CDN36X gateway operates as a DeviceNet slave. It supports Explicit Messages, Polled I/O
Messages, and Change-of-State (COS) I/O Messages of the predefined master/slave connection
set. The Explicit Unconnected Message Manager (UCMM) is not supported.
The I/O Messaging process consists of the DeviceNet master sending output data to the
CDN36X in the form of a Poll/COS Command Message, and the CDN36X returning input data
to the DeviceNet master in a Poll/COS Response Message. The difference between Poll and
Change-of-State is Polled I/O Messaging is initiated by the DeviceNet master and responded to
by the slave device. Change-of-State I/O Messaging is initiated by changes to the master’s
output data values or the slave’s input data values, causing the master or slave to immediately
transmit its new output or input data when it changes. Please refer to DeviceNet Specification
for detailed information on Polled I/O and Change-of-State I/O Messaging.
The output and input data bytes are typically mapped into data files inside the DeviceNet master.
These data files are exchanged with the user application program, which acts upon the received
input data and writes new output data to the DeviceNet master.
MKS Instruments, Inc.
D.I.P. Products Group
10
