Rockwell Automation 160 DEVICENET (DN1) MODULE FRN 1-2.XX - Manual (Page 52)

Publication 0160-5.5 - September 1997
Using 160-DN1 with DeviceNet Scanner 6-17
Explicit Messaging Explicit Messaging is a way of allowing the user to configure and
monitor a slave device’s parameters on the DeviceNet network. This
form of messaging is performed by copying data to and from the SLC
processor M0 and M1 file. Explicit Messaging can only be done by
the SLC processor to slave devices that are mapped in the scanner
module’s scan list.
How it Works
There are five steps to the Explicit Messaging process. The following
is a brief description of what happens during this process.
1. Format an M0 file transfer in the processor to send an Explicit
Message Request to the scanner module (download).
2. The scanner module transmits the Explicit Message Request to
the slave device over the DeviceNet network.
3. The slave device transmits the Explicit Message Response back
to the scanner and is queued into a file transfer buffer.
4. The processor uses an M1 file transfer to retrieve the Explicit
Message Response from the scanner’s buffer (upload).
5. Format an M0 file transfer with a Delete Response Command and
use the current transaction ID read in step 4. The transaction IDs
are deleted and can be reused.
It is important to note that there is a request message and a response
message whether you are reading or writing a parameter.
How to Format the Explicit
Message Transaction Block There are ten 32-word transaction blocks within the scanner module
reserved for Explicit Message Program Control. These transaction
blocks accommodate both downloading of Explicit Message Requests
and the uploading of Explicit Message Responses. The scanner mod-
ule can accommodate one request or response for each transaction
block. Each transaction block must be formatted as shown below.
Request Response
15 0 15 0
TXID command TXID status
port size port size
service MAC ID service MAC ID
class
service response
data
instance
attribute
service data