Physical Characteristics - Seagate ST15150N - Barracuda 4.3 GB Hard Drive Product Manual

ST15150N/ND/W/WD/WC/DC Product Manual, Rev. D
11.7.1
11.7.1.1
11.7.1.2
11.7.1.2.1
11.7.1.2.2

Physical characteristics

This section defines the connectors, cables, signals, terminators, and bus
timing 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 types 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 8 SCSI devices (including the host) may be daisy
chained together on non-wide systems (ST15150N/ND). Wide SCSI sys-
tems (ST15150W/WD/WC/DC) can have a maximum of 16 SCSI devices
(including the host) daisy chained together.
Terminate both ends of the daisy chain, but do not terminate any intermedi-
ate SCSI device. Refer to Section 11.7.3.3 for information about how to
terminate each model.
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 4 drives.
Single-ended I/O circuits
The maximum total cable length for use with drives having single-ended I/O
driver and receiver circuits is 6 meters (19.7 feet) when operating at line data
transfer rates of 5 Mbytes/second or less, and 3 meters (9.85 feet) when
operating at transfer rates greater than 5 Mbytes/second (fast SCSI). A stub
length of no more than 0.1 meter (0.33 foot) is allowed off the mainline
interconnection with any connected equipment. An ideal impedance match
with cable terminators implies a cable characteristic impedance of 132 ohms.
Single-ended I/O cable pin assignments for ST15150N drives are shown in
Table 14. Single-ended I/O cable pin assignments for ST15150W drives are
shown in Table 16. Single-ended I/O cable pin assignments for ST15150WC
drives are shown in Table 18.
Differential I/O circuits
The maximum total cable length for use with drives having differential I/O
drivers and receiver circuits is 25 meters (82 feet). A stub length of no more
than 0.2 meter (0.66 foot) is allowed off the mainline interconnection with any
connected equipment. An ideal impedance match with cable terminators
implies a cable characteristic impedance of 122 ohms. Differential I/O pin
assignments for ST15150ND drives are shown in Table 15. Differential
I/O pin assignments for ST15150WD drives are shown in Table 17.
Differential I/O pin assignments for ST15150DC drives are shown in
Table 19.
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