LSI LSI22915A, Руководство пользователя, Страница: 33 / 50

Detailed Installation Procedure 2-15
Version 1.3 Copyright © 2000–2003 by LSI Logic Corporation. All rights reserved.
2.2.6 Terminating the SCSI Bus
The devices that make up the SCSI bus are connected serially
(chained together) with SCSI cables. The SCSI devices at each end of
the SCSI bus must have their terminators active. The SCSI devices
between the two end devices must have their terminators removed or
disabled. The LSI22915A automatically enables its own termination when
it is at the end of the bus. (In other words, the LSI22915A terminates itself
if you connect only internal SCSI devices or only external SCSI devices.)
LVD SCSI devices are usually terminated with external terminators, but
sometimes termination is set with jumpers or with a switch on the device.
Refer to the device manufacturer’s instructions and to the computer’s
user’s manual to learn how to change termination settings on the device.
Caution: The LSI22915A may enable its own termination
erroneously if it is directly cabled to another SCSI device or
host adapter that uses the same sensing method.
(The LSI22915A senses SCSI devices by detecting the
ground signal on pin 50 of the SCSI cable.)
As stated above, the LSI22915A automatically terminates itself when it is
at the end of the SCSI bus. You can disable the autotermination feature
on SCSI Channel A by installing a jumper on the HDR3 connector, or on
SCSI channel B by installing a jumper on the HDR5 connector.
(
Figure 3.1 on page 3-2 shows where these headers are located.)
Note: There are very few reasons for disabling autotermination on
the LSI22915A. In nearly all situations it should be left
enabled (the default).
Figure 2.12 shows how jumpers on HDR3 and HDR5 control
autotermination:
Figure 2.12 Autotermination Jumpers
Autotermination Enabled (No Jumper Installed)
Termination Disabled (Jumper Installed)