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Introduction
1
Narrow and Wide SCSI Configurations
Single-ended and Differential Connections
Cabling
Termination
1-10
SCSI controllers can be daisy-chained together in a narrow
configuration using a 50-conductor, 8-bit cable to connect up to 8
SCSI devices on the bus. A wide configuration expands the bus to a
68-conductor, 16-bit bus that can handle up to 16 SCSI devices. Both
narrow (8-bit) and wide (16-bit) devices can be intermixed on a
wide SCSI bus (68-pin connector) only.
There are two electrical alternatives, single-ended and differential.
A differential connection uses a set of two conductors to maintain a
positive (+) and a negative (-) polarity. Cable lengths up to 25
meters can be used for differential systems. A single-ended
connection uses a single conductor with a common ground to
transfer each signal. This conÞguration should only be used over
short distances up to 6 meters.
Single-ended and differential connections are electronically
incompatible, and can not be mixed on the same physical bus. The
overall performance of the two is about the same.
Shielded and non-shielded cabling can be mixed on the same bus.
However, the non-shielded connections should be restricted to
internal cabinet applications only. All SCSI devices are configured
with a socket connector. The bus cable consists of the mating
pin-type connectors.
Both ends of the bus cable must be properly terminated. Interface
errors can be reduced if the termination voltage is maintained at the
extreme ends of the cable. All SCSI hardware include a setting
(usually with hardware jumpers) that allows the device to serve as
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Troubleshooting
