SCSI Connections
SCSI Restrictions
bus on this system, they must adhere to cabling, termination and bus length restrictions discussed in this chapter to assure functionality of the SCSI busses.
Because Ultra2 Wide Low-Voltage Differential SCSI is a relatively new technology, there can be products which are advertised as LVD compliant, but may not meet LVD specifications. Therefore, additional caution must be exercised when choosing Ultra2 Wide Low-Voltage Differential SCSI devices other than those supported by Hewlett-Packard Company to connect to the Ultra2 Wide Low-Voltage Differential SCSI bus on this system. For example, the cabling inside one of these devices in question may not have a differential impedance between 110 and 135 ohms and it may be constructed in a way such that the device has considerable crosstalk on critical signals, such as Reset, Select and Busy. Failure to strictly adhere to the Ultra2 Wide Low-Voltage Differential SCSI bus specifications will impact the performance of the LVD bus. The Ultra2 Wide Low-Voltage Differential interface is a much higher performance SCSI bus than previous SCSI buses and is more sensitive to adherence to the electrical specifications.
Low-voltage differential signaling specifications are described in the SCSI Parallel Interface-2(SPI-2)document and in the Electrical Characteristics of Low Voltage Differential Signaling (LVDS) Interface Circuits TIA/EIA-644document. Both of these documents can be obtained from:
Global Engineering Documents 15 Inverness Way East Englewood, CO 80112-5704
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