bus on this system, they must adhere to cabling, termination and bus
length restrictions discussed in this chapter to assure functionality of the
SCSI busses.
Because Ultra2 Wide Low-Voltage Differential SCSI is a relatively new
technology, there can be products which are advertised as LVD
compliant, but may not meet LVD specifications. Therefore, additional
caution must be exercised when choosing Ultra2 Wide Low-Voltage
Differential
SCSI
Hewlett-Packard Company to connect to the Ultra2 Wide Low-Voltage
Differential SCSI bus on this system. For example, the cabling inside one
of these devices in question may not have a differential impedance
between 110 and 135 ohms and it may be constructed in a way such that
the device has considerable crosstalk on critical signals, such as Reset,
Select and Busy. Failure to strictly adhere to the Ultra2 Wide
Low-Voltage Differential SCSI bus specifications will impact the
performance of the LVD bus. The Ultra2 Wide Low-Voltage Differential
interface is a much higher performance SCSI bus than previous SCSI
buses and is more sensitive to adherence to the electrical specifications.
Low-voltage differential signaling specifications are described in the
SCSI Parallel Interface-2 (SPI-2) document and in the Electrical
Characteristics of Low Voltage Differential Signaling (LVDS) Interface
Circuits TIA/EIA-644 document. Both of these documents can be
obtained from:
Global Engineering Documents
15 Inverness Way East
Englewood, CO 80112-5704
800-854-7179 or 303-397-7956
Chapter 4
devices
other
than
SCSI Connections
SCSI Restrictions
those
supported
by
87