Rockwell Automation Allen-Bradley 842D, Руководство пользователя

Страница: 27 / 58

Chapter
5
Configuring a Scanner to
Communicate with the Encoder
Chapter Objectives
Chapter 5 provides instructions for configuring a PLC or SLC scanner
to communicate with the encoder.
Required Equipment and
Software
Before configuring the scanner, your PC must be:
• Running RSNetWorx for DeviceNet. Refer to
http://www.software.rockwell.com for more information.
• Connected to and communicating with the DeviceNet network
using a DeviceNet interface such as a 1784-PCD card or a
1770-KFD adapter.
Operating Modes of the
Encoder
There are two fundamentally different DeviceNet protocols:
• Explicit messaging
• I/O messaging
Explicit messaging
Explicit messaging is used for modifying the device configurations,
reading diagnostic values, program upload / download, etc.
Characteristics of explicit messaging:
• Very flexible
• Less efficient because each device must interpret and generate a
response
• "Unbound" connections ("Hit and Run")
• Contents of the data field:
– Protocol information
– Instructions for service to be performed
– Internal address to which the service is to be applied
I/O messaging
I/O messaging is used for fast or time-critical data transfer. All of the
8 data bytes of the CAN telegram can be used for data transmission.
Characteristics of I/O messaging:
• Less flexible