| Many systems use single-ended SCSI because of the lower cost and large base
of available devices. An increasing number of systems and devices use
differential (HVD) SCSI because of the improved noise immunity, increased drive
stability and the longer attainable cable lengths.
Paralan SCSI converters make communication between both types of devices
possible. Hardware and software remain the same: the converter is transparent to
all devices. Plug your single-ended cable into one end of the converter and the
differential (HVD) cable into the other end. All SCSI devices will be available.
All Paralan SCSI Converters conform to the full SCSI ANSI standard. This
includes managing the arbitration and disconnect/reconnect features of the
latest systems, down to the SASI communications of earlier systems. They manage
any possible signal conflicts such that they remain transparent to both HVD and
single-ended devices.
New ASIC Version
Paralan introduced the industry's first Fast (10 Mbyte/sec)
single/differential (HVD) SCSI converter in 1992. These new models, using our
own ASIC, are
Ultra SCSI compatible: 20 Mbyte/sec for 8-bit (narrow) and 40 Mbyte/sec
for 16-bit (wide) SCSI.
Narrow and wide devices may be placed in the same system. Call Sierra for
details.
Extend Total Cable Length
By using two converters in series an extension up to 200 feet (60 m) is
obtainable. See "Operation as a SCSI Extender," below.
Handle Bus Noise, Termination Problems
Auto Senseâ„¢ detects correct termination power. All models have internal
terminations which may be disabled if the converter is not placed at the end of
the bus.
Operation as a Single-ended/HVD SCSI Converter
Since SCSI is a bi-directional bus, a single converter is used to interconnect
single-ended SCSI IDs with HVD SCSI IDs. Place the converter within 19 feet (6
m), or 10 feet (3 m) for fast SCSI, or 5 feet (1.5 m) for Ultra SCSI, of the
single-ended SCSI port. Up to 82 feet (25 m) of cable may be placed between the
converter and HVD port, or 87 to 100 feet (26.5-31 m) overall. Paralan is the
first to produce SCSI converters that enable the maximum SCSI cable length on
both ends, even through Ultra speeds.
Operation as a SCSI Extender
Single ended:
Two Paralan converters can extend the single-ended SCSI bus up to 200 feet (60
m). Place each converter within 19 feet (6 m), or 10 feet (3 m) for fast SCSI,
or 5 feet (1.5 m) for Ultra SCSI, of the two single-ended SCSI ports. Then
connect up to 160 feet (50 m) of differential SCSI cable between them.
Differential (HVD): Two Paralan converters can extend the HVD SCSI bus
up to 174 feet (53 m). Connect up to 82 feet (25 m) of differential SCSI cable
to each converter. Then connect up to 10 feet (3 m) of single-ended cable
between them.
For HVD SCSI extension, the SCSI RegeneratoRâ„¢s (SIR-Dx series) are usually a
better choice for distances up to 320 feet (100 m). To 4 km (13,000 feet):
If longer distances are required, refer to Paralan Fiber Optic SCSI Extenders
(QA and FX series).
Available Models
SCSI converter/extender models are available for both wide (16-bit) or narrow
(8-bit); and in stand-alone or board-level versions:
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