HP 10343B Operating Manual page 80

Introduction
SCSI Overview
The Small Computer Sytems Interface (SCSI) is a standard that maybe
used for fast transfers of data between Computers and Mass Storage
Devices. This includes standards for printers and scanners on the SCSI
Bus.
The standard hardware of the 8-Bit SCSI Bus is a 50 wire cable that
interconnects up to a maximum of eight devices on the bus. On this cable
is defined to be eight data lines with one parity line. Parity is odd and the
use of the parity is optional for SCSI.
There are two SCSI Bus Standards:
• Single-Ended; and
• Differential
The Single-Ended bus runs at TTL levels with a logical 1 (active) being a
low level on the bus. The Differential bus uses two lines per signal with
the lines moving between approximately 2 and 3 volts.
Each device on the bus is assigned a device number of 1 through 8. If
there is a condition of more than one device asking for the bus at one
time, the highest numbered device gets the bus. Each device is assigned
one line on the data bus for a device ID.
With SCSI, the host computer is not the bus controller. The device that
the host calls is the bus controller. Most often this is a mass storage
device.
The host computer is called the INITIATOR and the device that the host
calls on the bus is called the TARGET.
SCSI Overview
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