This bit is active when the 6K controller disables the drive. This may be simply that the drive is disabled via the DRIVE command. If any other TASF bits in the 6K are active, they may indicate that the drive is not shutdown because of the DRIVE command but because of some other fault in the controller. For instance, a Maximum Position Error (Bit 23) will cause the 6K to shut the drive down. If the Drive Fault bit is active, it is due to the drive being faulted.
Check the other TASF bits for controller faults and see the appropriate Frequently Asked Question for further help in resolving it.
If the Drive Fault bit (Bit 14) is active, then see the Frequently Asked Question titled "TASF Bit 14 -- Drive Fault" for more information.
Issue a DRIVE1 on the appropriate axis to re-enable the drive.