HP LTO Ultrium 4 drives technical reference manual, volume 2: software integration 37
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Automation Control Interface (ACI)
The Automation Control Interface (ACI) protocol allows the activities of the drive to be coordinated
within a library. The protocol has been designed so that it can be made into a standard feature of
tape drives. It provides a rich and extensible functionality to allow automation manufactures to add
value in their application of it.
The interface is a serial bus with additional control lines, designed to connect the Ultrium tape drive
to an automation controller in a tape library. Each tape drive position has a separate ACI
connection allowing communication to the drive via its RS 422 serial port.
The ACI protocol provides the following fundamental functions:
• Coordinating the automation controller and the tape drive for Load and Unload operations
• Allowing the automation controller to retrieve information from the tape drive
• Setting tape drive configuration information
In addition, the following functions may be supported depending on the way that the tape library is
configured:
• Providing upload and download of firmware images
• Providing access to Cartridge Memory contents
• Providing a protocol for passing SCSI commands to the tape drive over the interface.
The ACI protocol allows for “packetized” SCSI commands to be sent from the attached controller
and submitted to the tape drive as if they have been received on the drive’s own SCSI bus. For
example, the ACI protocol allows the sending of load/unload commands from a specially defined
automation command set to cause drive action. This ability enables the attached controller to access
and control the drive in exactly the same way as it would over the SCSI bus.
NOTE: Ultrium SCSI Parallel drives implement a limited subset of the SCSI commands, including
INQUIRY, LOG SENSE, LOG SELECT and MODE SENSE.
The following notes should be regarded as supplementing the ACI protocol specification rather than
replacing them. Please refer to the specification for further implementation details. These notes refer
to the “standard” automation drive variant. Different behavior may be exhibited in certain areas for
specific OEM variants as requested by OEMs.
Modes of usage through ACI
Slave to a library controller
The ACI can receive commands such as LOAD and UNLOAD from a specially defined automation
command set to control the action of the drive.
Most tape libraries need to have a means of communication between controller and tape drives, to
enable correct synchronization of mechanical operations between drive and picker arm. For
instance, in a soft load capable device such as an Ultrium drive, the picker must let go of the
