Specifications

Glossary-5
Glossary
APA-1460 SlimSCSI Technical Reference
Stock Number: 510671-00 Rev. A Page: -5
Print Spec Number: 492966-00
Current Date: 8/22/94 ECN Date: 8/30/94
to a SCSI bus cable. The device may be an
initiator, a target, or capable of both types
of operation.
SCSI ID
A unique identifier assigned to SCSI
devices that enables them to communicate
with a computer when they are attached to
a host adapter via the SCSI bus. Each SCSI
host adapter board has eight available SCSI
IDs with the numbers 0 through 7 (or 0
through 15 for Wide SCSI adapters).
Usually the host adapter itself is assigned
SCSI ID 7, and hard disk devices are
assigned to SCSI IDs 0 and 1.
SCSI Protocol Controller
A device that provides an input/output
interface between an ISA expansion bus
and a SCSI bus. Adaptec's AIC-6360 pro-
vide these functions on a single computer
chip.
Small Computer Systems Interface
See SCSI.
Synchronous Data Transfer
A high-speed data transfer method in
which data on the SCSI bus is clocked with
fixed-length, fixed-frequency strobe pulses.
The acknowledgments may be delayed sev-
eral clock periods from the data requests.
Synchronous data transfer can be used only
for data transmission on the SCSI bus. It
cannot be used for Command, Message,
and Status transmission.
Synchronous Data Transfer Negotiation
The process in which the host adapter and
the peripherals on the SCSI bus negotiate
the data transfer frequency and the delay
between requests and acknowledgments.
This negotiation process is required for
synchronous data transfer.
T
Target (or Target Device)
A SCSI device that performs an operation
requested by an initiator. The initiator is
usually the host adapter. The target may be
a peripheral device such as a disk drive
performing a data transfer for an initiator.
Termination
A physical requirement of the SCSI bus.
The devices at the physical ends of the SCSI
bus must have terminating resistors either
installed or enabled; devices in the middle
of the bus must have terminating resistors
either removed or disabled. Proper termi-
nation allows electrical signals to be trans-
mitted reliably on the SCSI bus.
W
Word
A 2-byte (16-bit) unit of data.
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