Rockwell Automation 20-COMM-Q ControlNet Adapter - Manual (Page 131)

Using Explicit Messaging 6-3
20-COMM-C/Q ControlNet Adapter User Manual
Publication 20COMM-UM003F-EN-P
Performing Explicit
Messages There are five basic events in the Explicit Messaging process. The details of
each step will vary depending on the type of controller being used. See the
documentation for your controller.
Important: There must be a request message and a response message for all
Explicit Messages, whether you are reading or writing data.
Figure 6.1 Explicit Message Process
For information on the maximum number of Explicit Messages that can be
executed at a time, see the documentation for the scanner or bridge and/or
controller that is being used.
Event Description
➊
You format the required data and set up the ladder logic program to send an Explicit
Message request to the scanner or bridge module (download).
➋
The scanner or bridge module transmits the Explicit Message Request to the slave device
over the network.
➌
The slave device transmits the Explicit Message Response back to the scanner. The data is
stored in the scanner buffer.
➍
The controller retrieves the Explicit Message Response from the scanner’s buffer (upload).
➎ The Explicit Message is complete.
➎
➊
➋ ➌
➍
Complete Explicit
Message
Retrieve Explicit
Message Response
Set up and send Explicit
Message Request
(optional redundancy)
Channel A
Channel B
ControlNet
Network