U42093-J-Z716-1-74 Operating Manual
Appendix B

Addressing, Structures and Operation

Fibre Channel and SCSI systems employdifferent methods of addressing
devices.The inclusion of a bridge or router requires that a method of translating
deviceIDs be implemented so that each SCSI device is mapped to the appro-
priateFibre Channel LUN. The SCSI bus establishes bus connections between
devices.Targets on the SCSI bus may internally address logical units. The
addressingof a specific SCSI device is represented by the BUS:TARGET:LUN
triplet.
Whena Fibre Channel initiator initializes on an arbitrated loop, the first order of
businessis to determine what devices exist on the loop. Device discovery is
performed,and an FCP target device list is built. Each device is queried for FCP
logicalunits. The logical units are the actual devices that the operating system
will address.When an initiator addresses a logical unit, the LUN field used is
consistent inform with the SCC defined fields. All current Fibre Channel host
busadapter drivers are consistent with these methods. The addressing used is
the SCC LogicalUnit Addressing and Peripheral Device Addressing methods,
shownin Table “SCC Addressing structure” and “Peripheral DeviceAddressing
LUN structure”. First leveladdressing is supported, so only the first 2 bytes of
the 8 byteFCP LUN are used.
SCC Addressing structure
PeripheralDevice Addressing LUN structure
Bit
Byte 76543210
n AddressMethod Address Method Specific
n+1 Address Method Specific
Bit
Byte 76543210
n00 Bus
n+1 Target/LUN