The code FF8B in your ABB ACS800 drive indicates a warning related to the configuration of optional I/O extension modules or fieldbus modules. These modules are used to expand the drive's functionality by providing additional digital or analog input/output (I/O) capabilities or allowing communication with other devices on a network.

The FF8B warning signifies that there's a mismatch between the way the I/O extension module or fieldbus module is configured and how it's being used in the application program of the ABB ACS800 drive. There are two main possibilities:

• Incorrect Program Settings: The program might be referencing an input or output signal that's defined as being connected to the optional module, but the communication with the module itself hasn't been properly set up in the drive parameters. Check parameter group 98 OPTION MODULES.
• Module Configuration Issue: The optional module itself might not be configured correctly for the desired functionality within your application.