Rockwell Automation 1756-XXXX ControlLogix Digital I/O Modules - Manual (Page 230)

230 Rockwell Automation Publication 1756-UM058G-EN-P - November 2012
Appendix C Use Ladder Logic To Perform Run Time Services and Reconfiguration
The illustration shows an example WHO ladder logic application.
The rungs perform these functions:
• Rung 0 constantly polls the module for WHO status. To conserve
bandwidth, only poll for status when necessary.
• Rung 1 extracts the product type and catalog code.
• Rung 2 extracts the module’s major and minor revisions.
• Rung 3 extracts the module’s status information.
• Rung 4 extracts the vendor ID and serial number.
• Rung 5 extracts the module’s ASCII text string and the length of the text
string in bytes.