1.3.2The SCSI Interface

The SCSI functionality for the LSIU80ALVD is contained within the LSI53C895A. The LSI53C895A connects directly to the SCSI bus and generates signal timing and bus protocol in compliance with the SCSI standard.

The SCSI interface on the LSIU80ALVD operates as an 8-bit or 16-bit interface. It supports 8-bit or 16-bit, synchronous and asynchronous, LVD or SE, Fast, Ultra and Ultra2 SCSI protocols in various combinations. The interface is made through connectors J2 and J3 (see Figure 2.1). Internal connector J2 is a 68-pin HD right angle latching connector. External connector J3 is a shielded 68-pin HD right angle connector that protrudes through the back panel bracket.

An on-board LED (labeled Activity) indicates SCSI bus activity.

LVD/SE dual mode, active termination is provided on the LSIU80ALVD. Termination is automatically disabled when both SCSI connectors are used.

The LSIU80ALVD supplies SCSI bus TERMPWR through a blocking diode and a self-resetting 1.5 A short circuit protection device.

A 40 MHz oscillator is installed on the LSIU80ALVD to provide the clock frequency to the LSI53C895A that is necessary to support Ultra2 SCSI transfers of up to 80 Mbytes/s.

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Using the LSIU80ALVD