Terminating a SCSI Device
ID: q92765
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The information in this article applies to:
SUMMARY
The release notes mention the importance of terminating SCSI devices
on both ends. They also mention that the Future Domain 845 and 1660
cards do not have termination power. These two issues are related, but
they are not the same.
The SCSI bus must be terminated on both ends of the bus. Someone on
the SCSI bus needs to provide termination power (5V) to allow the
pull-up resistors to terminate the bus properly.
The FD 845 has termination resistor packs on the card. This card does
not place 5V on the termination power wire on the SCSI bus. These
cards rely on the attached SCSI devices to provide 5V on the
termination pin, so your SCSI device must be configured to provide
termination power. Termination power is generally supplied by all SCSI
devices, but is typically switchable. If no one on the bus provides
termination power, your SCSI bus will not function correctly.
For example, to terminate the card/bus on the internal side, set your
CD-ROM to provide termination power. Leave the resistor packs in the
FD. Place a terminator on the CD-ROM drive (if that is the last
device).
MORE INFORMATION
On SCSI adapters that have both an internal and an external connector,
the "ends" of the SCSI bus are defined as follows:
- If you have only external devices (no internal devices), one end of
the bus is the last device in the external chain. The other end of
the bus is the card itself. In this case, the last device in the chain
must be terminated, and the resistor packs on the card itself must be
in place.
-or-
- If you have only internal devices (no external devices), one end of
the bus is the last device in the internal chain. The other end of
the bus is the external connector on the adapter (or the card itself).
In this case, the last device in the internal chain must be terminated.
You have a choice of leaving the resistor packs on the card, or
removing them and placing a SCSI terminator on the external connector.
-or-
- If you have both internal and external devices attached, the ends of
the bus are defined as the last device in the external chain and the
last device in the internal chain. In this case, the resistor packs
on the card itself must be removed, and only the last device in each
must be terminated.
Additional query words:
Keywords : kbhw
Version : 3.1
Platform : WINDOWS
Issue type :
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