Mixing Single-Ended, High-Voltage Differential, And Low-Voltage Differential Devices; Cable Lengths; Termination - HP SureStore 220mx User Manual

Operating This Jukebox on a SCSI Bus
The SCSI Bus and This Jukebox
Mixing Single-Ended, High-Voltage Differential, and
Low-Voltage Differential Devices
On a low-voltage differential (LVD) bus, if the jukebox senses a
single-ended device on the bus, the bus will be operated as a single-ended
bus. You must not mix high-voltage differential buses with either
low-voltage differential or single-ended buses. High-voltage signals are on
different pins and may damage low-voltage differential circuits.

Cable Lengths

This jukebox can use either a single-ended or low-voltage differential
bus. When using a single-ended bus, you have 8.50 feet (2.59 metres)
available for an external bus. (3 metres allowable minus 0.41 metres for
internal cabling.)
If you are using a low-voltage differential bus, you have 38.04 feet (11.59
metres) available for an external bus. (12 metres allowable minus 0.41
metres for internal cabling.)

Termination

• Refer to the documentation that comes with your particular adapter
to see how to apply termination.
• Use active terminators on single-ended buses to reduce noise
sensitivity. Use low-voltage differential terminators if using a
low-voltage differential bus. If you have a multimode (SE/LVD) host
adapter, you can use SE/LVD terminators. These terminators can
sense which mode is being used.
• Never terminate the bus at any place except the physical ends.
Terminating the bus in the middle will probably cause the bus to
become inoperable or operate in a state that could cause data loss.
• If devices are on both sides of the host bus adapter (such as hard
drives internal to the host computer and a jukebox external to the
host computer) make sure that there is no termination on the host
bus adapter. Termination must be only on the device inside the
computer that is farthest away (on the bus) from the host bus adapter,
B-10 Appendix B