Seagate ST39102LW/LC, ST34502LW/LC manual Drive termination

22 Cheetah 9LP Installation Guide, Rev. B

Drive termination

If you are installing a Cheetah drive in a system that has other SCSI devices installed, terminate only the end devices on the SCSI chain. A SCSI “device” is any disc drive, scanner, tape backup unit, or other piece of hardware connected to your sys- tem using the SCSI bus.

Note. Use active (ANSI SCSI-2 Alternative 2) single-ended ter- minators when terminating a bus operating in single- ended mode. Use SPI-2-compliant active low voltage dif- ferential terminators when terminating a SCSI Ultra2 bus operating in LVD mode.

The top example in Figure 2 shows an internal hard disc at one end of the SCSI bus with the SCSI controller at the other end (both are terminated). The bottom example shows two additional SCSI devices connected externally—this means the SCSI con- troller is no longer on the end of the SCSI chain and should not be terminated.

Note. Some controllers prefer to remain terminated even if they are in the middle of the chain. Also, some controllers treat the internal and external chains as separate logical buses. This means you may need to terminate both the first and last devices on both logical buses to achieve proper termination. If necessary, refer to your system or controller documentation to see how this is handled in your particular system.

These drives do not have on-board terminators, so you must ter- minate external to the drive when termination is required. For ST39102LC and ST34502LC drives, this is normally accom-