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CHAPTER 3: Configuration and Internal LEDs
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Termination at the Other End(s) of the Segment (JP1 and JP12):
The JP1 and
JP12 jumper posts control whether or not the Expander provides TERMPWR
output to support remote termination.
To explain: Most of the current generation of SCSI host adapters, disk
drives, and other devices have built-in internal terminators, like those in the
Expander, that can be used to terminate the SCSI bus if that device happens to
be the first or last device attached to the bus. The remote ends of the SCSI-bus
segments that you’ll be attaching to the Expander will probably be able to be
terminated this way.
But if, on a SCSI segment that will be attached to the Expander, the first or
last device (or both) don’t have an internal terminator, you will need to attach
an external terminator to that device instead. (I) That external terminator will
need to draw its power from a “terminator power” (TERMPWR) voltage that
must be present on the SCSI bus. Most SCSI devices can be set to provide
TERMPWR.
NOTE
It’s easy to make mistakes when installing external SCSI termination. If
you’ll need to do so, please call Black Box Technical Support to discuss
your application.
If the remote termination for the segments that will be attached to the
Expander can be handled with another device’s internal terminator, or with
an external terminator that gets its TERMPWR from some other device(s), you
can leave jumper posts JP1 and JP12 in their factory-default setting (no
jumpers installed). But if you’ll need to use an external terminator
that gets its
TERMPWR from the Expander
for remote termination on a segment attached to
either of the Expander‘s ports, install a jumper on the posts for that port.
Install a jumper on JP12 to have the Expander provide TERMPWR on Port A.
Install a jumper on JP1 to have the Expander provide TERMPWR on Port B.
Refer to Figure 3-1 on the previous page. In that illustration, the host adapter
and disk drive both have enabled internal terminators. But if the host adapter
didn’t have an internal terminator and couldn’t provide TERMPWR, you
would have to install a jumper on the Expander’s JP12 posts. If the same were
true of the disk drive, you would have to install a jumper on the Expander’s
JP1 posts.
Summary of Contents for IC540A
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