Rockwell Automation 5720 DriveLogix System - Manual (Page 186)

Publication 20D-UM002C-EN-P - November 2003
8-6 Communicating with Devices on a DeviceNet Link
Defining the data blocks
How you configure the DeviceNet devices determines how many words you
use per device. The 1788-DNBO card supports a
maximum of:
• 124 32-bit words of input data
• 123 32-bit words of output data
• 32 32-bit words of status data
Once you define the scanlist, you define how the data for the devices maps
into the input, output, and status data blocks. Use the Input, Output, or Status
tabs to define the associated data block
Use the AutoMap button to simplify defining the data block for each
DeviceNet device. The above screens show how many 32-bit words are
mapped for the devices on this example network. These words map directly
into the array tags that the software creates for the 1788-DNBO card.
Most DeviceNet devices support 16-bit words. Take care how you map these
into the 32-bit words used in RSLogix 5000 programming software.
RSNetWorx for DeviceNet lets you DINT-align the device data. While this
might simplify the organization of the data, it might also limit the data you
have available.
Accessing DeviceNet
Devices I/O information is presented as a structure of multiple fields, which depend
on the specific features of the I/O module. The name of the structure is based
on the location of the I/O module in the system. Each I/O tag is