Seagate ST31200N, Руководство по эксплуатации продукта

Страница: 59 / 78

Product Manual - Hawk 1LP Family SCSI-2 (Volume 1), Rev. C 51
_____________________________________________________________________________________
11.6.2.2.3 General cable characteristics
In general, cables having the characteristic impedance’s given in 11.6.2.2.1 and 11.6.2.2.2 are not available;
however, impedance’s that are somewhat lower are satisfactory. A characteristic impedance of 100 ohm +10%
is recommended for unshielded flat or twisted pair ribbon cable. However, most available cables have a
somewhat lower characteristic impedance. To minimize discontinuities and signal reflections, cables of
different impedance’s should not be used in the same bus. Implementations may require trade-offs in shielding
effectiveness, cable length, the number of loads, 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 SCSI transfer rates.
For models ST31200N/ND:
Only nonshielded cable connectors are applicable. A 50 conductor flat cable or 25 twisted pair cable shall be
used. A minimum conductor size of 28 AWG should be used to minimize noise effects.
Suggested nonshielded flat cable part numbers are:
Flat cable - 35M-3365-50
Twisted pair - Spectra Twist in flat 455-248-50
For model ST31200NC/ST3620NC:
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. Cable mounted connectors would not be used in such a case. Installation with
cable mounted connectors are not recommended.
11.6.3 Mating connector requirements
11.6.3.1 Mating connectors for models ST31200N/ND
The nonshielded cable connector shall be a 50 conductor connector consisting of two rows of 25 female
contacts with adjacent contacts 100 mils apart.
Recommended mating flat cable connector part numbers are:
Closed end 3M-3425-7000 W/O Strain Relief, No Center Key
(for cable 3M-3425-7050 With Strain Relief, No Center Key
ends)* Dupont-66900-290 With Strain Relief, With Center Key
Open end 3M-3425-6000 W/O Strain Relief, No Center Key
(In Daisy-chain) 3M-3425-6050 With Strain Relief, No Center Key
Dupont-66900-250 With Strain Relief, With Center Key
*See Figure 11.6.3-2.
The drive device connector is a nonshielded 50 conductor connector consisting of two rows of 25 male pins
with adjacent pins 100 mils apart. The connector is keyed (see Figure 11.6.3-1a).