Scsi Interface Cable Requirements; Mating Connectors - Seagate ST39173N Product Manual

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9.6.3

SCSI interface cable requirements

The characteristics of cables used to connect SCSI-3 parallel interface devices are discussed in detail in sec-
tion 6 of ANSI Standard X3T10/1142D. The cable characteristics that must be considered when interconnect-
ing the drives described in this manual in a SCSI-3 parallel, daisy-chain interconnected system are:
• characteristic impedance (see section 6.1)
• propagation delay (see section 6.1)
• cumulative length (see sections 6.4 and 6.5)
• stub length (see sections 6.4 and 6.5)
• device spacing (see sections 6.4 and 6.5)
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.
9.6.4

Mating connectors

Part numbers for the different type connectors that mate with the various Barracuda 9LP I/O connectors are
given in the sections following.
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 100 mils 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 10.
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 11a).
Mating panel mount connector: 3M-CHE-2050-J01A10-KLE.
Barracuda 9LP Product Manual, Rev. C
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