Cheetah 36XL Product Manual, Rev. E | 61 |
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.
Note. For LVD operation, twisted pair cables are recommended. For LVD Fast-40 operation, twisted pair cables are strongly recommended. For Fast-80 operation, twisted pair cables are required.
ST336705LC, ST318405LC and ST39205LC
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 Standard X3T10/1302D, section 6. For LC model drives, installations with connectors on cables are not recommended.
9.6.4Mating connectors
Part numbers for the different type connectors that mate with the various Cheetah 36XL I/O connectors are given in the sections following.
9.6.4.1Mating 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.
Recommended mating flat cable connector part numbers are:
Amp Model 786096-7 Female, 68-pin, panel mount
Amp Model 786090-7 Female, 68-pin, cable mount
Amp Model 749925-5 (50 mil conductor centers, 28 or 30 AWG wire)
Use two, 34 conductor, 50 mil center flat cable with this connector. This type connector can only be used on cable ends. [1]
Amp Model 88-5870-294-5 W/O Strain Relief (25 mil conductor centers, 30 AWG wire).
Use either on cable ends or in cable middle section for daisy-chain installations [1].
Amp Model 1-480420-0 Power connector 4 circuit housing
Berg 69307-012 | 12-position, 2 x 6, 2 mm receptacle housing |
[1]See Figure 21.
The drive device connector is a nonshielded 68 conductor connector consisting of two rows of 34 female pins with adjacent pins 50 mils apart. The connector is keyed by means of its shape (see Figure 22).
9.6.4.2Mating connectors for LC model drives
The nonshielded connector shall be an 80-conductor connector consisting of two rows of 40 contacts with adja- cent contacts 50 (1.27 mm) mils apart (see Figure 23). I/O connection using a cable is not recommended. The length and size of the host equipment DC power carrying conductors from the DC power source to the host equipment 80-pin disc drive interface connector(s) should be strictly designed according to proper power trans- mission design concepts. No possibility for the equipment user to attach an 80-pin cable/connector should be allowed, since the length of the DC power carrying conductors could not be controlled and therefore could become too long for safe power transmission to the drive. Daisy-chain 80-conductor cables should especially not be allowed, since the power-carrying conductors on the 80-conductor interface were not intended to sup- port a series of drives.
To insure that both drive connector and host equipment mating connector mate properly, both drive connector and host equipment mating connector must meet the provisions of “SFF-8046 Specification for 80-pin connec- tor for SCSI Disk Drives.”
