Rockwell Automation 1747-SDN SLC 500 DeviceNet Scanner Module User Manual - Manual (Page 145)

Publication 1747-UM655B-EN-P - June 2007
Explicit Message Program Control 145
The module requires a precisely-formatted M0 and M1 file transfer
size of 32 words including words 224…255. The module uses the file
memory content as a client/server request.
How to Format the Explicit Message Transaction Block
Up to ten 32-word transaction blocks may be queued within the
module for Explicit Message Program Control. The transaction blocks
accommodate both the download of Explicit Message Requests and
the upload of Explicit Message Responses.
The module can accommodate one request or response for each
transaction block. You must format each transaction block as shown
in the following figure.
The transaction block is divided into two parts.
•
Transaction header – contains information that identifies the
transaction to the scanner and processor.
•
Transaction body – in a request, this contains the DeviceNet
Class, Instance, Attribute and Service Data portion of the
transaction. In a response, this contains only the response
message.
Each of the data attributes in the transaction header are one byte in
length.
•
Command/status – for each download, you assign a command
code to instruct the scanner how to administer the request.
Transaction Header
(3 words) TXID CMD/Status
Port Size
Service MAC ID
Word 224
Word 225
Word 226
Transaction Body (29
Words)
One Word = Two Bytes = 16 Bits
Word 255
15 0