Monitoring Discrepancy Error - Secure Input Group

What does FB MON Bit 2 mean?

A discrepancy has been detected between the 'Secure1' and 'Secure2' input channels in the FB MON function block. These inputs are used to switch off the evaluation of 'MonIn(x)' inputs. A discrepancy here means the redundant secure inputs are not in agreement, which can lead to unintended disabling of monitoring functions, potentially bypassing safety.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Review the discrepancy time parameter for the Secure input pair in the FB MON configuration; adjust if the application legitimately has different timing requirements.

2. 4

   Monitor the 'Secure1' and 'Secure2' signals in real-time using diagnostic tools to identify which channel is deviating.