Adaptec USBXchange User Manual

Contents

U se r’s G ui de : US B X ch a ng e • 22Understanding SCSISCSI (pronounced “scuzzy”) stands for Small Computer SystemInterface. SCSI is an industry standard computer interface for connectingup to seven SCSI devices (such as hard disk drives, CD-ROM drives, andscanners) to a common SCSI bus.A SCSI bus is an electrical pathway consisting of a SCSI adapter (such asthe USBXchange adapter) installed in a computer and one or more SCSIdevices. When more than one SCSI device is connected to your computer,it is referred to as a SCSI chain. SCSI cables are used to connect thedevices to the SCSI card. For the SCSI bus to function properly, SCSI IDsmust be assigned to the SCSI devices and the SCSI adapter, and the SCSIbus must be properly terminated.The LED display located on top of your USBXchange will flash toindicate activity in the SCSI bus.SCSI IDsEach device attached to the USBXchange, as well as the adapter itself,must be assigned a unique SCSI ID number from 0 to 7. A SCSI IDuniquely identifies each SCSI device on the SCSI bus and determinespriority when two or more devices are trying to use the SCSI bus at thesame time. The USBXchange is preset to SCSI ID 7, which gives it the highestpriority on the SCSI bus. In Windows 98 and Windows 2000 you can use the Device Managerto view the SCSI ID and other information about each installed SCSIdevice. If you installed Adaptec EZ-SCSI® software (sold separately), youcan use the SCSIExplorer™ utility to view the SCSI ID and otherinformation about each installed SCSI device. On a Macintosh, you can use the SCSIProbe software to viewinformation about each installed SCSI device.Terminating the SCSI BusTo ensure reliable communication on the SCSI bus, terminators must beinstalled (or enabled) on the devices at the physical ends of the SCSI bus.The terminators on all devices between the physical ends must beremoved (or disabled). SCSI termination is required whether you haveone or many SCSI devices connected. Termination on the USBXchange ispermanently enabled, since it is always at one end of the SCSI bus.