LSI LSI21002 User Manual page 32

2.2.4.1 Internal SCSI Connections
2-16
Remember: The LSI21002 is also on the SCSI bus, and its termination
is automatically enabled when it is connected to the end of
the bus.
LVD 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 your computer user's
manual for information on how to identify the terminator
setting of each device and how to change it.
Caution: The autoenable/disable sensing feature of Channel A on
the LSI21002 may enable termination erroneously if it is
directly cabled to another SCSI device or host adapter
using the same sensing method. The LSI21002 senses
SCSI devices by detecting the ground signal on
conductor 50 of a 68-conductor SCSI cable or conductor 22
of a 50-conductor SCSI cable. Only the SE/LVD terminators
on Channel B will always remain on.
When connecting another host adapter to a connector, termination must
be disabled on the board that is not at the end of the bus through
software control.
The LSI21002 automatically controls SCSI bus termination for four
different bus configurations, depending on the use of connectors (see
Figure 2.1). The four bus configurations are:
•
Only for internal SCSI connections,
•
Only for an external SCSI connection, and
•
Connections to both internal and external SCSI connectors
•
Connections to both internal connectors.
Termination on the LSI21002 for these four different bus configurations
are discussed below. Please note that only SE termination control is
allowed on Channel A.
If only internal SCSI device connections on the host adapter have been
made, then terminate the last internal device on the SCSI bus. You must
disable the termination on all other devices. Termination on the LSI21002
Installing the LSI21002