Seagate BARRACUDA 2LP, Руководство по эксплуатации продукта

Страница: 81 / 102

Barracuda 2LP Product Manual, Rev. D 71
implies a cable characteristic impedance of 122 ohms. Differential I/O cable
pin assignments for ST31250ND and ST32550ND drives are shown in Table
18. Differential I/O cable pin assignments for ST31250WD and ST32550WD
drives are shown in Table 20.
Differential I/O pin assignments for ST31250DC and ST32550DC drives are
shown in Table 19. WC and DC model drives do not require an I/O cable.
They are designed to be connected directly to a back panel .
11.7.1.2.3 General cable characteristics
Note. Use only non-shielded cable connectors with ST31250N/ND and
ST32550N/ND drives. Use a 50-conductor flat cable or 25-conductor
twisted-pair cable. Use a minimum conductor size of 28 AWG to
minimize noise effects. The following non-shielded flat cables (or
equivalents) may be used:
Flat cable 35M-3365-50
Twisted-pair cable Spectra twist in flat 455-248-50
In general, cables having the characteristic impedances given in Sections
11.7.1.2.1 and 11.7.1.2.2 are not available; however, impedances that are
lower are satisfactory. A characteristic impedance of 100 ohm
+
10% is
recommended for unshielded flat or twisted-pair ribbon cable. To minimize
discontinuities and signal reflections, cables of different impedances should
not be used in the same bus. Your specific setup may require tradeoffs in
shielding effectiveness, cable length, 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 to maintain adequate margin at fast SCSI transfer
rates.
11.7.2 Connector requirements
ST31250N/ND and ST32550N/ND drives
Use a non-shielded 50-conductor cable connector consisting of two rows of
25 female contacts with adjacent centers 100 mils apart.
Recommended mating flat cable connector part numbers:
Closed end 3M-3425-7000 Without strain relief,
(for cable ends) no center key
3M-3425-7050 With strain relief, no center key
Berg-66900-290 With strain relief and center key
Open end 3M-3425-6000 Without strain relief,
(in daisy chain) no center key
3M-3425-6050 With strain relief, no center key
Berg-66900-250 With strain relief and center key
The drive device connector is a non-shielded 50-conductor connector
consisting of two rows of 25 male pins with adjacent pins 100 mils apart. The
connector is keyed (see Figure 31).
Recommended mating panel mount connector part number:
3M-CHE-2050-J01A10-KLE