Seagate ST373454 Manual download pdf (Page 68)

58 Cheetah 15K.3 SCSI Product Manual, Rev. G

Table 14: Interface transfer rates supported

9.6.3 SCSI interface cable requirements

The characteristics of cables used to connect parallel interface drives are discussed in the ANSI standards ref-

erenced in this section.

9.6.3.1 Cable requirements

The characteristics of cables used to connect Ultra160 and Ultra320 SCSI parallel interface devices are dis-

cussed in detail in section 6 of the SPI-4 (ANSI T10/1365D) standard. The cable characteristics that must be

considered when interconnecting the drives described in this manual in a SCSI parallel, daisy-chain intercon-

nected system are:

• characteristic impedance (see T10/1365D Rev. 8 Sections 6.3.3, 6.3.4, and 6.3.5)

• propagation delay (see T10/1365D Rev. 8 Sections 6.3.6 and 6.3.7)

• cumulative length (see T10/1365D Rev. 8 Sections 6.6 and 6.8)

• stub length (see T10/1365D Rev. 8 Sections 6.6 and 6.9)

• device spacing (see T10/1365D Rev. 8 Sections 6.6 and 6.9)

To minimize discontinuances and signal reflections, cables of different impedances should not be used on 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, Fast-40,

Fast-80, and Fast-160 SCSI transfer rates.

Note. For LVD operation, twisted pair cables are recommended. For LVD Fast-40 operation, twisted pair

cables are

strongly

recommended. For Fast-80 or Fast-160 operation, twisted pair cables are

required

All LC model drives:

The 80-pin connector option is intended for use on drives that plug directly into backplane connector in the host

equipment. In such installations, all backplane wiring segments are subject to the electromagnetic concepts

presented in SPI-4 Standard T10/1365D section 6. For LC model drives, installations with connectors on

cables are not recommended.

9.6.4 Mating connectors

Part numbers for the different type connectors that mate with the various Cheetah 15K.3 SCSI I/O connectors

are given in the sections following.

9.6.4.1 Mating connectors for LW model drives

The nonshielded cable connector shall be a 68 conductor connector consisting of two rows of 34 male contacts

with adjacent contacts 0.050 inch (1.27 mm) apart.

Interface type/

drive models

Maximum transfer rate

Asynchronous Fast-5 Fast-10

Fast-20

(Ultra)

Fast-40

(Ultra2)

Fast-80

(Ultra160)

Fast-160

(Ultra320)

SE ST373453LW/LC

ST336753LW/LC

ST318453LW/LC

yes yes yes yes no no no

LVD ST373453LW/LC

ST336753LW/LC

ST318453LW/LC

yes yes yes yes yes yes yes

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