Advantech PCA-6187 user manual Understanding SCSI, SCSI IDs

Models: PCA-6187

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7.2 Understanding SCSI

7.2 Understanding SCSI

SCSI (pronounced .scuzzy.) stands for Small Computer Systems Inter- face. SCSI is an industry standard computer interface for connecting SCSI devices to a common SCSI bus.

A SCSI bus is an electrical pathway that consists of a SCSI interface installed in a computer and one or more SCSI devices. SCSI cables are used to connect the devices to the SCSI interface. For the SCSI bus to function properly, a unique SCSI ID must be assigned to the SCSI inter- face and each SCSI device connected to it, and the SCSI bus must be properly terminated.

7.3 SCSI IDs

Each device attached to the SCSI bus, as well as the SCSI controller itself, must be assigned a unique SCSI ID number from 0 to 15. A SCSI ID uniquely identifies each SCSI device on the SCSI bus and determines priority when two or more devices are trying to use the SCSI bus at the same time.

Refer o the device.s documentation to set the SCSI ID. Here are some general guidelines for SCSI IDs:

For internal SCSI devices, the SCSI ID usually is set by configuring a jumper on the device.

For external SCSI devices, the SCSI ID usually is set with a switch on the back of the device.

SCSI ID numbers don.t have to sequential, as long as the SCSI control- ler and each device has a different number.

For example, you can have an internal SCSI device with ID 0, and an external SCSI device with ID 6.

SCSI ID 7 has the highest priority on the SCSI bus. The priority of the remaining IDs, in descending order, is 6 to 0, then 15 to 8.

The on-boards SCSI interface is preset to SCSI ID 7 and should not be changed. This gives it the highest priority on the SCSI bus.

Most internal SCSI hard disk drives come from the factory pre-set to SCSI ID 0.

If you have 8-bit (or Narrow) SCSI devices, they must use SCSI IDs 0, 1, 2, 3, 4, 5, or 6. SCSI ID 0 is recommended for the first SCSI hard disk drive.

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Advantech PCA-6187 user manual Understanding SCSI, SCSI IDs