LSI U40HVD - Manual (Page 33)

Detailed Installation Procedure 2-17
Remember: The LSIU40HVD is also on the SCSI bus; its termination is
automatically enabled when it is connected to the end of
the bus.
Differential peripheral devices are normally terminated with external
terminators, but are sometimes set with jumpers or with a switch on the
peripheral. Refer to the peripheral manufacturer’s instructions and to the
user’s manual for your computer for information on how to identify the
terminator setting of each device and how to change it.
Caution: The auto-enable/disable sensing feature on the
LSIU40HVD may enable termination erroneously if it is
directly cabled to another SCSI device or host adapter
using the same sensing method. The LSIU40HVD senses
SCSI devices by detecting the ground signal on conductor
50 of a 68-conductor SCSI cable. If you use an adapter to
connect 8-bit devices externally with a 50-conductor SCSI
cable, the ground signal is detected on conductor 34.
The LSIU40HVD automatically covers SCSI bus termination for three
different bus configurations, depending on your use of the connectors on
the LSIU40HVD (see
Figure 2.1 ). The three bus configurations are:
•
only for internal SCSI connections
•
only for external SCSI connections
•
for both internal and external SCSI connections
Termination on the LSIU40HVD for these three different bus
configurations is discussed below.
2.2.4.1 Internal SCSI Connections
If internal SCSI device connections to the host adapter have been made,
you must terminate the last internal device on the SCSI bus. You must
disable the termination on all other devices. Termination on the host
adapter is automatically enabled in this case.
Figure 2.12 shows an example of how termination is determined for this
SCSI bus configuration.