Scsi Physical Interface - Seagate ST12450W Product Manual

ST12450W/WD Product Manual, Rev. A
11.7
11.7.1
11.7.1.1
11.7.1.2

SCSI physical interface

Figure 17 shows the locations of the physical interface components for the
drive. Locations of the DC power connector, the SCSI interface connector,
the I/O line terminators, and the drive select and option select headers are
shown.
Details of the physical, electrical, and logical characteristics are given below.
The SCSI operational aspects of Seagate drive interfaces are provided in the
SCSI-2 Interface Product Manual.
SCSI I/O
Connector
Pin 1
Figure 17. Barracuda 2, 2HP physical interface
Physical characteristics
This section defines the connectors, cables, signals, and terminators needed
to implement the SCSI interface.
Physical description
You can daisy chain multiple SCSI devices on a common cable if each device
has the same type of drivers and receivers (all single-ended or all differen-
tial). Devices having single-ended interface circuits cannot be on the same
daisy chain with devices having a differential interface circuit. Both ends of
the cable must be terminated. All signals are common between SCSI
devices. A maximum of 16 SCSI devices (including the host) may be daisy
chained together.
Terminate both ends of the daisy chain, but do not terminate any intermedi-
ate SCSI device. The ST12450W drives are equipped with permanently
mounted IC terminators, which you can turn on or off using the Enable Drive
Terminator jumper on pins 11 and 12 of J4. The differential (ST12450WD)
drives do not have on-board terminators.
Cable requirements
Sections 11.7.1.2.1, 11.7.1.2.2, and 11.7.1.2.3 describe the single-ended,
differential, and general cable requirements for Barracuda 2, 2HP drives.
J4
J5
DC Power
Connector
J01
53