Advantech PCA-6277-B, Manual

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Chapter 7 SCSI Setup and Configurations 9 5
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
interface 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 deter-
mines 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 swetch
on the back of the device.
•
SCSI ID numbers don’t have to sequential, as long as the SCSI
controller 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 remianing 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 deveices, 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.