I/o modules and devicenet, I/o modules and devicenet -21 – Rockwell Automation 198 Series C Modular DeviceNet Starter Auxiliary User Manual User Manual
Page 42
3-21 Operation
Publication 198-UM002A-EN-P December 2001
Modular DSA system using explicit messaging. Explicit messages contain the following
information:
•
Service – Tells the device what action to take in response to the message. Service
reads information from a device and for writes information to a device.
•
Class – Tells the device which object class to send the service to. Classes are
identified by their numeric “class code”. Appendix A contains a complete list of the
classes that are implemented in the Modular DSA system.
•
Instance – Each object class can contain one or more “instances” of that class in a
given device. Instances are numbered starting with instance 1. The value “0” refers to
the class itself, not any individual instance of that class. Appendix A contains a
complete list of instances that are implemented for each class in the Modular DSA
system.
•
Attribute – An attribute is a single piece of information related to an object class or
instance. Attributes are numbered starting at attribute number 1. Note that attributes
need to be numbered sequentially. Appendix A contains a complete list of attributes
for each class and instances implemented in the Modular DSA system.
I/O Modules and DeviceNet
The discrete inputs and discrete outputs of the MDSA I/O modules are modeled on
DeviceNet by DeviceNet Discrete Input Point Objects (DIPs) and DeviceNet Discrete
Output Point Objects (DOPs), respectively. Each DIP and each DOP is assigned an instance
number based on the physical location of its I/O module on the MDSA back-plane. Instance
numbers are assigned starting with instance number 1, which is the first DIP or DOP that is
on the I/O module closest to the MDSA DeviceNet module (Cat. Nos. 198-DN, 198-DNG)
on the back-plane.
EXAMPLE
Sample Module Assembly
Table 3.2 Sample Module Assembly
Mod 0
Mod 1
Mod 2
Mod 3
Mod 4
Mod 5
Mod 6
Mod/Net
Out 1
In 1
In 1
In 1
In 1
In 1
I/O
Out 2
In 2
In 2
In 2
In 2
In 2
In 3
Out 1
Out 1
In 4
Cat. No.
198-DNG
Cat. No.
198-OW2
Cat. No.
198-IB4
Cat. No.
198-IB2XOW1
Cat. No.
198-IB2XOB1
Cat. No.
198-IA2
Cat. No.
198-IB2S