Rockwell Automation VSM500 Integrated Drive/Motor DeviceNet Option Board - Manual (Page 45)

Using Explicit Messaging 6-1
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Using Explicit Messaging
This chapter provides information about using explicit messaging. It includes
information on about using explicit messaging, how to format explicit messages, and
an example of an SLC ladder logic program.
Important: In order to use explicit messaging, you must have already configured the
VSM500 unit and DeviceNet option (see chapter 3) and the scanner (see
chapter 4).
6.1 About Explicit Messaging
Explicit messaging is a way of configuring and monitoring a slave device’s parameters
on the DeviceNet network. This form of messaging is performed by copying data to
and from the SLC controller M0 and M1 file. Explicit messaging can only be done by
the SLC controller to slave devices that are mapped in the scanner module’s scan list.
6.2 Using Explicit Messaging
With an SLC 500, there are five steps to the explicit messaging process.
Step 1. Format an M0 file transfer in the processor to send an explicit message
request to the scanner module (download).
Step 2. The scanner module transmits the explicit message request to the slave
device over the DeviceNet network.
Step 3. The slave device transmits the explicit message response back to the
scanner and is queued into a file transfer buffer.
Step 4. The processor uses an M1 file transfer to retrieve the explicit message
response from the scanner’s buffer (upload).
Step 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.
Important: There must be a request message and an response message whether
you are reading or writing a parameter.