Allen-Bradley 1756 Series, User Manual, Page: 40 / 136

40 Rockwell Automation Publication 1756-UM013B-EN-P - October 2019
Chapter 2 Features Common to 1756 ControlLogix Digital Safety I/O Modules
Module Data
Quality Reporting
The digital safety I/O modules indicate the quality of channel data that is
returned to the owner-controller. Data quality represents accuracy. Levels of data
quality are reported via module input tags.
These input tags indicate the level of data quality.
• I.Ptxx.Fault - This tag indicates that the reported channel data is
inaccurate and cannot be trusted for use in your application. Do not use
the reported channel data for control.
If the tag is set to 1, you cannot trust the data reported. You must
troubleshoot the module to correct the cause of the inaccuracy.
Example causes of inaccurate data include:
– Field Power Loss condition (output modules)
– Short Circuit condition (output modules)
We recommend that you troubleshoot the module for the typical causes
first.
• I.Ptxx.Uncertain - This tag indicates that the reported channel data can be
inaccurate but the degree of inaccuracy is unknown. We recommend that
you do not use the reported channel data for control.
If the module sets this tag to 1, you know that the data can be inaccurate.
You must troubleshoot the module to discover what degree of
inaccuracy exists.
Example cause of uncertain data includes:
– Module is operating outside its designed operating temperature range
IMPORTANT Once the condition that causes the Fault or Uncertain tag to change to 1 is
removed, the tag automatically resets to 0. The Logix Designer application
controls the tags. You cannot change the status of the tags.
Keep in mind that in some system configurations, the tag is not reset
immediately after the condition is removed. The tag typically resets after a
small delay.
IMPORTANT We strongly recommend that you monitor the tags in your program to make
sure that the application is operating as expected with accurate channel input
data.