Rockwell Automation 2098-DSD-xxx Ultra3000 Digital Servo Drives with DeviceNet - Manual (Page 13)

Publication 2098-RM004A-EN-P – August 2002
Overview 1-3
Predefined Master/Slave Connection Set
A set of messaging connections that facilitate communications and is
typically seen in a master/slave relationship is known as the
Predefined Master/Slave Connection set. The master is the device that
gathers and distributes I/O data for the process controller. A
DeviceNet master scans its slave devices based on a scan list it
contains. Each slave device returns I/O data to its master device.
The I/O data exchanged over this connection is pre-defined.
Explicit Response/Request Messages
Explicit Request messages are used to perform operations such as
reading and writing parameter values. Explicit Response messages
indicate the results of the attempt to service an Explicit Request
message.
Polled I/O Command/Response Messages
The Poll Command is an I/O message transmitted by the master
device. A Poll Command is directed toward a specific slave device. A
separate Poll Command must be sent to each slave device that is to be
polled. The Poll Response is the I/O message that the slave device
transmits back to the master device.
Change-of-State/Cyclic Messages
A Change-of-State/Cyclic message is directed towards a single specific
node (master or slave). An Acknowledge response may or may not be
returned to this message. A Change-of-State message is sent at a
user-configurable heart rate or whenever a data change occurs. A
Cyclic message is sent only at a user-configurable rate.