Rockwell Automation RECOMM-ENET EtherNet/IP Communications Module - Manual (Page 185)

Glossary Glossary-7
zero data - When communications are disrupted (for example, a
cable is disconnected), the module and drive can respond with zero
data. Zero data results in the drive receiving zero as values for
command data. If the drive was running and using the reference
from the module, it will stay running but at zero reference.