User`s guide

6
SCSI Bus Signal Converters
Note
The discussion of the DWZZA-series SCSI bus signal converters
in this chapter is limited to the models, applications, cables, and
configurations applicable to the SBB shelves. The capabilities and use of
these converters in other environments or with other SCSI systems is not
within the scope of this manual.
The SBB shelf SCSI buses are 8-bit, single-ended, SCSI–2 buses. Some
controllers and hosts, or their SCSI adapters, use a 16-bit, differential SCSI
bus. Singled-ended and differential buses are incompatible. The SCSI protocol
will disable these buses when they are connected together.
SCSI bus signal converters permits connecting these buses together without
modifying the SCSI devices. For an SBB shelf the DWZZA-series SCSI bus signal
converters are used to establish compatibility between the host SCSI bus and the
SBB bus and extend the length of the SCSI bus.
Two SCSI bus signal converters are used with StorageWorks products—the
DWZZA–AA and the DWZZA–VA. Electrically and operationally these models are
identical. The primary differences are as follows:
• The DWZZA–AA is a desktop model with a self-contained power supply
that can be connected to an SBB shelf or a DWZZA–VA converter. The
DWZZA–AA has two female cable connectors—a 68-pin, high-density and a
50-pin, low-density.
• The DWZZA–VA is and installed in slot 0 of an SBB shelf. It has a single
female cable connector—a 68-pin, high-density.
Note
The DWZZA–VA input connector is a 68-pin, differential connector. There
is no provision for connecting a 50-pin, single-ended connector to the
DWZZA–VA.
In this chapter, SCSI buses are either a single-ended or a differential physical
bus or a single-ended physical bus connected to a differential physical bus by a
SCSI bus signal converter, a logical bus.
SCSI Bus Signal Converters 6–1