Mating Connectors - Seagate ST34501N Product Manual

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9.6.3.1 Single-ended I/O circuits ("N" and "W" models)
The maximum total cable length allowed with drives having single-ended I/O driver and receiver circuits
depends on several factors. Table 12 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.
Table 12: Cable characteristics for single-ended circuits
Maximum number of
I/O transfer rate devices on line
<10 M transfers/s 8 (reg. SCSI bus)
<10 M transfers/s 16 (wide SCSI bus)
<20 M transfers/s 4 (reg./wide SCSI bus)
<20 M transfers/s 8 (reg./wide SCSI bus)
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 13a, 13b, and 13d.
9.6.3.2 Differential I/O circuits ("WD" and "DC" models)
The maximum total cable length allowed with drives having differential I/O driver and receiver circuits is 25
meters (82 feet). Twisted-pair cable (either twisted-flat or discreet wire twisted pairs) should be used with differ-
ential I/O transceiver circuits. A stub length of no more than 0.2 meter (0.66 foot) is allowed off the mainline
interconnection with any connected equipment. The stub length is measured from the transceiver to the con-
nection to the mainline SCSI bus. The spacing of devices on the mainline SCSI bus should be at least three
times the stub length to avoid clustering (Refer to Annex C of X3T10/1071D). This restriction easily allows the
16 device IDs that the SCSI 16 bit wide bus can address. These values are from the ANSI SCSI-3 Fast-20
(also called Ultra SCSI) specification X3T10/1071D.
An ideal impedance match with cable terminators implies a cable characteristic impedance of 122 ohms. Dif-
ferential I/O pin assignments are shown in Tables 13c and 13e.
9.6.4

Mating connectors

Part numbers for the different type connectors that mate with the various Cheetah 4LP I/O connectors are
given in the sections following.
Cheetah 4LP Product Manual, Rev. B
Maximum cable length
allowed
6 meters (19.7 ft.)
6 meters (19.7 ft.)
3 meters (9.8 ft.)
1.5 meters (4.9 ft.)
Transmission line impedance
REQ/ACK Other signals
90 ± 6 Ohms 90 ± 10 Ohms
90 ± 6 Ohms 90 ± 10 Ohms
90 ± 6 Ohms 90 ± 10 Ohms
90 ± 6 Ohms 90 ± 10 Ohms