Seagate ST336605LW/LC/LCV 用户手册
66
Cheetah 73LP Product Manual, Rev. E
Single-ended I/O pin assignments for LC models are shown in Table 14. The LC model does not require an I/O
cable. It is designed to connect directly to a backpanel connector.
cable. It is designed to connect directly to a backpanel connector.
9.7.1.3
Cables for low voltage differential drivers/receivers
The SPI-3 specification for differential impedance for LVD cables is 122.5 ± 12.5 ohms.
The maximum SCSI bus length between the terminators for a SCSI LVD point-to-point system (one initiator
and one target) is 25 meters (82 feet).
and one target) is 25 meters (82 feet).
The maximum SCSI bus length between the terminators for a SCSI LVD multidrop system (up to 16 total SCSI
devices) is 12 meters (39.37 feet). However, implementation of this 12-meter total length is dependent on the
configuration of the system and the choice of cable. See Tables 17 and 18 for examples of recommended SCSI
LVD cable types and lengths.
devices) is 12 meters (39.37 feet). However, implementation of this 12-meter total length is dependent on the
configuration of the system and the choice of cable. See Tables 17 and 18 for examples of recommended SCSI
LVD cable types and lengths.
It should be noted from the data in Tables 17 and 18 that shielded round twisted-pair cables can be used to
implement a 12-meter system, while twist-n-flat cables cannot be used to implement a 12-meter system due to
higher levels of attenuation and crosstalk. In addition, twist-n-flat cables with shorter sections of twist allow
greater crosstalk and their lengths must be reduced as shown in Table 18.
implement a 12-meter system, while twist-n-flat cables cannot be used to implement a 12-meter system due to
higher levels of attenuation and crosstalk. In addition, twist-n-flat cables with shorter sections of twist allow
greater crosstalk and their lengths must be reduced as shown in Table 18.
9.8
Terminator requirements
Caution:
These drives do not have onboard internal terminators. The user, systems integrator or host equip-
ment manufacturer must provide a terminator arrangement external to the drive when termination is
required. For LW/LWV drives, use terminator modules that plug between the SCSI I/O cable and
the drive I/O connector or on the end of a short I/O cable stub extending past the last cable connec-
tor. LC/LCV drives are designed to be plugged into a backpanel connector without cabling.
ment manufacturer must provide a terminator arrangement external to the drive when termination is
required. For LW/LWV drives, use terminator modules that plug between the SCSI I/O cable and
the drive I/O connector or on the end of a short I/O cable stub extending past the last cable connec-
tor. LC/LCV drives are designed to be plugged into a backpanel connector without cabling.
Table 17:
Example shielded round twisted-pair cables—into a multi-drive backplane
Cable
description
description
Differential
impedance,
nominal
impedance,
nominal
Single-ended
impedance,
nominal
impedance,
nominal
Single-ended
capacitance,
maximum
capacitance,
maximum
Time
delay,
nominal
delay,
nominal
Conductor DC
resistance,
nominal
resistance,
nominal
Maximum shielded round
twisted-pair cable length
for U160/U320
twisted-pair cable length
for U160/U320
30 AWG
solid
solid
130 ohms
90 ohms
17 pF/ft
1.36 ns/ft
0.113 ohms/ft
12 meters minus the SCSI
trace length of the backplane
trace length of the backplane
28 AWG
stranded
stranded
123 ohms
80 ohms
19 pF/ft
1.54 ns/ft
0.067 ohms/ft
12 meters minus the SCSI
trace length of the backplane
trace length of the backplane
28 AWG
stranded
stranded
132 ohms
85 ohms
20 pF/ft
1.50 ns/ft
0.065 ohms/ft
12 meters minus the SCSI
trace length of the backplane
trace length of the backplane
Table 18:
Example twist-n-flat cables—into a multi-drive backplane
Cable description
Differential
impedance,
nominal
impedance,
nominal
Single-ended
impedance,
nominal
impedance,
nominal
Single-ended
capacitance,
maximum
capacitance,
maximum
Time
delay,
nominal
delay,
nominal
Conductor DC
resistance,
nominal
resistance,
nominal
Maximum
twist-n-flat
cable length
for U160
transfer rate
twist-n-flat
cable length
for U160
transfer rate
TPE, 22.25" twist, 1.75"
flat, (24" flat to flat), 30
AWG solid tinned copper
flat, (24" flat to flat), 30
AWG solid tinned copper
131 ohms
93 ohms
15.3 pF/ft
1.45 ns/ft 0.105 ohms/ft
6.1 meters
(20.0 feet)
(20.0 feet)
TPE, 8.1" twist, 1.75" flat,
(9.85" flat to flat), 30 AWG
solid tinned copper
(9.85" flat to flat), 30 AWG
solid tinned copper
131 ohms
93 ohms
15.3 pF/ft
1.45 ns/ft 0.105 ohms/ft
4.9 meters
(16.66 feet)
(16.66 feet)
TPE, 4.25" twist, 1.75"
flat, (6" flat to flat), 30
AWG solid tinned copper
flat, (6" flat to flat), 30
AWG solid tinned copper
131 ohms
93 ohms
15.3 pF/ft
1.45 ns/ft 0.105 ohms/ft
3.04 meters
(10.0 feet)
(10.0 feet)