Take the machinery offline. Put the controller keyswitch into "Program" mode.
It contains vital security patches addressing vulnerabilities related to unauthorized firmware updates and communication port exploitation.
RSLogix 5000 firmware 20.12 (listed as 20.012 in the PCDC) is a maintenance release for ControlLogix and CompactLogix controllers that resolves specific hardware anomalies and ensures compatibility with version 20 software. The firmware supports various legacy hardware, including CompactLogix L3x/L2x and 1756-L6x controllers, and requires a two-step upgrade process for older revisions. For detailed release notes on specific hardware, visit Rockwell Automation Literature .
If your system uses redundancy, standard firmware like 20.012 will not work; you must use specific redundancy firmware (typically ending in a different suffix, like 20.05x ).