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Introduction
1
1-8
All SCSI devices are required to operate using asynchronous data
transfers. Synchronous transfers are optional, and negotiated
between the host and target during power-up.
There are two electrical alternatives, single-ended and differential.
They are electronically incompatible and can not be mixed on the
same physical bus. Cable lengths up to 25 meters can be used for
differential systems. Single-ended configurations can be up to 6
meters. 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
a terminator. Where possible, the SCSI devices serving as initiators
should supply terminator voltage; which again, is usually a
hardware jumper on the deviceÕs SCSI adapter or controller card.
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