Seagate ST336732LC Product Manual page 79

Cheetah X15 36LP Product Manual, Rev. D
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 21 and 22 for examples of recommended SCSI
LVD cable types and lengths.
Note from these tables that shielded round twister-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 leels 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 22.
Table 21: Example shielded round twister pair cables into a multi-drive backplane
Defferential
Cable
Impedance,
Description
nominal
30 AWG 130 ohms
solid
28 AWG 123 ohms
standed
28 AWG 132 ohms
stranded
Table 22: Example Twist-n-flat cables into a multi-drive backplane
Differential
Cable
impedance,
Description
nominal
TPE, 22.25" twist, 131 ohms
1.75" flat, (24" flat
to flat), 30 AWG
solid tinned coper)
TPE, 8.1" twist, 131 ohms
1.75" flat, (9.85" flat
to flat), 30 AWG
solid tinned coper)
TPE, 4.25" twist, 131 ohms
1.75" flat, (6" flat to
flat), 30 AWG solid
tinned coper)
Single-ended Single-ended
impedance, capacitance,
nominal maximum
90 ohms 17 pF/ft
80 ohms 19 pF/ft
85 ohms 20 pF/ft
Single- Single-
ended ended
impedance, capacitance,
nominal maximum
93 ohms 15.3 pF/ft
93 ohms 15.3 pF/ft
93 ohms 15.3 pF/ft
Conductor DC
Time Delay,
resistance,
nominal
nominal
1.36 ns/ft 0.113 ohms/ft
1.54 ns/ft 0.067 ohms/ft
1.50 ns/ft 0.065 ohms/ft
Time Conductor DC
Delay, resistance,
nominal nominal
1.45 ns/ft 0.105 ohms/ft
1.45 ns/ft 0.105 ohms/ft
1.45 ns/ft 0.105 ohms/ft
69
Maximum shielded
round twister-pair cable
length for
Ultra160/Ultra320
12 meters minus the SCSI
trace length of the back-
plane
12 meters minus the SCSI
trace length of the back-
plane
12 meters minus the SCSI
trace length of the back-
plane
Twist-n-flat
Cable Length
Ultra320 Ultra160
transfer transfer
rate rate
3.05 meters 6.1 meters
(10.0 ft) (20.0 ft)
2.45 meters 4.9 meters
(8.33 ft) (16.66 ft)
1.52 meters 3.04 meters
(5.0 ft) (10.0 ft)