Rockwell Automation 2098-IPD-020-DN Ultra5000 Series Intelligent Positioning Drives with DeviceNet Reference Manual - Manual (Page 23)

Publication 2098-RM002A-EN-P – October 2001
DeviceNet Overview 3-3
polled. The Poll Response is the I/O message that the slave device
transmits back to the master device.
I/O Messaging and Explicit
Messaging with DeviceNet
You can configure and monitor the drive with either I/O Messaging or
Explicit Messaging. I/O messages are for time-critical, control-oriented
data. I/O messages typically are used for moving predefined data
repeatedly with minimum protocol overhead. Explicit Messages
provide multi-purpose, point-to-point communication paths between
two devices. Explicit Messaging typically would not be used to
exchange data periodically since I/O Messages have a higher priority
and lower protocol overhead than Explicit Messages. However,
Explicit Messages have more flexibility by specifying a service to be
performed and a specific address.
Selecting Input and Output
Assemblies for I/O
Messages
The Ultra5000 with DeviceNet provides sixteen generic Input and
Output Assemblies. The choice of which Input and/or Output
Assembly to use should be based on the type of information that is
appropriate in the particular system. The I/O Assemblies are mapped
to the first four 32-bit values of the Long Integer (DNetIntArray) and
Floating-point (DNetFltArray) arrays
The Ultra5000 has no pre-defined information stored in these
locations. The contents of the locations are under user program
control, and it is the responsibility of the user program(s) to update
and utilize the values as necessary.
The choice of which Input and Output Assembly to use should be
based on what sort of information is appropriate in a particular
system. You should keep in mind that larger assemblies utilize more
network bandwidth. Information on the data format of all the
Assemblies is given in Assembly Object (Class ID 04H) on page 4-11.