Mating Connectors - Seagate ST34520N - Medalist 4.55 GB Hard Drive Product Manual

Medalist Pro Product Manual, Rev. D
To minimize discontinuances and signal reflections, cables of different impedances should not be used in the
same bus. Implementations may require trade-offs in shielding effectiveness, cable length, number of loads
and spacing, transfer rates, and cost to achieve satisfactory system operation. If shielded and unshielded
cables are mixed within the same SCSI bus, the effect of impedance mismatch must be carefully considered.
Proper impedance matching is especially important in order to maintain adequate margin at FAST-20 and
FAST-40 SCSI transfer rates.
For "WC" and "LC" models:
The 80 pin connector option is intended for use on drives that plug directly into a PCB or wall/bracket mounted
connector in the host equipment. In such installations, all backplane wiring segments are subject to the electro-
magnetic concepts presented in Standard X3T10/1142D, section 6. For "WC" and "LC" model drives, installa-
tions with connectors on cables are not recommended.
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 15 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 15: Cable characteristics for single-ended circuits
Maximum number of
I/O transfer rate devices on line
< 10 M transfers/s 8 (reg. SCSI bus)
16 (wide SCSI bus)
< 10 M transfers/s
< 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 16, 17, and 19.
9.6.4

Mating connectors

Part numbers for the different type connectors that mate with the various Medalist Pro I/O connectors are given
in the following sections.
9.6.4.1 Mating connectors for "N" models
The nonshielded cable connector shall be a 50 conductor connector consisting of two rows of 25 female con-
tacts with adjacent contacts 0.1 inches (2.54 mm) apart.
Recommended mating flat cable connector part numbers are:
Closed end 3M-3425-7000
(for cable 3M-3425-7050
ends)[1] Dupont-66900-290
Open end 3M-3425-6000
(In daisy chain)[1] 3M-3425-6050
Dupont-66900-250
[1] See Figure 19.
The drive device connector is a nonshielded 50 conductor connector consisting of two rows of 25 male pins
with adjacent pins 0.1 inches (2.54 mm) apart. The connector is keyed (see Figure 20).
Mating panel mount connector: 3M-CHE-2050-J01A10-KLE.
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.)
W/O Strain Relief, No Center Key
With Strain Relief, No Center Key
With Strain Relief, With Center Key
W/O Strain Relief, No Center Key
With Strain Relief, No Center Key
With Strain Relief, With Center Key
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
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