For all SCSI devices, including disks, CD-ROMs, read/write optical drives, tapes, target mode, and initiator devices, the location code format is AA-BB-CC-S,L. The AA-BB fields identify the location code of the SCSI adapter controlling the SCSI device. . A value of 00 for the AA field indicates the controlling adapter card is located in the CPU drawer or system unit, depending on the type of system. . The BB field identifies the I/O bus and slot containing the card. The first digit indicates the I/O bus. It is 0 for the standard I/O bus and 1 for the optional I/O bus. The second digit is the slot on the indicated I/O bus containing the card. A value of 00 for the BB field indicates the standard SCSI controller. . The CC field identifies the card's SCSI bus that the device is attached to. For a card that provides only a single SCSI bus, this field will be set to 00. Otherwise, a value of 00 indicates a device attached to the card's internal SCSI bus and a value of 01 indicates a device attached to the card's external SCSI bus. . The S,L field identifies the SCSI ID and logical unit number (LUN) of the SCSI device. The S value indicates the SCSI ID, and the L value indicates the LUN.