Seagate ST34555N, Руководство по эксплуатации продукта

Страница: 62 / 82

52 Hawk 4XL Product Manual, Rev. A
Model “W” drives use nonshielded cable connectors. A 68 conductor flat cable or 34 twisted pair cable shall be
used with connectors listed in 9.6.4. A minimum conductor size of 28 AWG should be used to minimize noise
effects.
Suggested nonshielded flat cable part numbers are:
Flat cable - 35M-3365-68 Twisted pair - Spectra Twist in flat 455-248-68
9.6.3.1 Single-ended I/O circuits
The maximum total cable length allowed with drives having single-ended I/O driver and receiver circuits
depends on several factors. Table 11 lists the maximum lengths allowed for different configurations of drive
usage. These values are from the ANSI SCSI-3 Fast-20 (also called Ultra SCSI) specification X3T10/1071D.
All device I/O lines must have equal to or less than 25 pf capacitance to ground, measured at the beginning of
the stub.
Notes:
[1] The spacing of devices on the mainline SCSI bus should be at least three times the stub length (defined
below) to avoid clustering (Refer to Annex C of X3T10/1071D). Based on this criteria, it may be that 8
devices will not actually work on 1.5 meters of line ( .1 x 3 x 7 = 2.1 meters).
A stub length of no more than 0.1 meter (0.33 foot) is allowed off the mainline interconnection with any con-
nected equipment. The stub length is measured from the transceiver to the connection to the mainline SCSI
bus.
Single-ended I/O pin assignments are shown in Tables 12 and 13.
Table 11: Cable characteristics for single-ended circuits
I/O transfer rate
Maximum number of
devices on line Maximum cable
length allowed
Transmission line impedance
REQ/ACK Other signals
< 10 M transfers/s 8 (reg. SCSI bus) 6 meters (19.7 ft.) 90 ± 6 Ohms 90 ± 10 Ohms
< 10 M transfers/s
16 (wide SCSI bus) 6 meters (19.7 ft.) 90 ± 6 Ohms 90 ± 10 Ohms
< 20 M transfers/s 4 (reg./wide SCSI bus) 3 meters (9.8 ft.) [1] 90 ± 6 Ohms 90 ± 10 Ohms
< 20 M transfers/s 8 (reg./wide SCSI bus) 1.5 meters (4.9 ft.) [1] 90 ± 6 Ohms 90 ± 10 Ohms