Because RSLogix 500 is a licensed industrial product, it is not available as a simple "one-click" public download. You must use official Rockwell Automation channels:
There is no official "Version 81". Versions follow a major.minor format – 8.10, 8.20, etc. If you see "8.1", it usually means 8.10. rslogix 500 version 81 download install
Rockwell Automation distributes this software through its Product Compatibility and Download Center (PCDC) . RSLogix 500 Ver 8 | PLCtalk - Interactive Q & A Because RSLogix 500 is a licensed industrial product,