Adaptec 2940W Installation Manual page 5

If the AHA-2940 detects that a cable is connected
to both its internal and external SCSI connector,
then it disables its terminators (the AHA-2940 lies
between the ends of the SCSI bus).
We recommend that you leave the AHA-2940 set to
its default setting of Automatic. If you want to man-
ually enable or disable the AHA-2940 termination
setting, see Configuring the Host Adapter on page 8.
Terminating the AHA-2940W
Termination on the AHA-2940W itself is also con-
trolled by software commands via the SCSISelect util-
ity. The default setting is set to Low ON/High ON.
This means that termination is enabled for both the
low and the high bytes of the 16-bit Wide SCSI bus.
The low byte controls the 8-bit SCSI; the low and
high bytes together control 16-bit Wide SCSI.
If you are using both internal connectors on the
AHA-2940W, or an internal connector and the exter-
nal connector, you must change the termination set-
ting from the default setting. The following table
lists the termination configurations.
Devices Connected to AHA-2940W
68-pin internal connector only
68-pin external connector only
68-pin internal and 68-pin external connectors
50-pin internal connector only
50-pin and 68-pin internal connectors
50-pin internal and 68-pin external connectors
Terminating SCSI Devices
Read the device's documentation to determine how
to enable or disable termination on your particular
SCSI device(s). On most internal SCSI devices the ter-
mination setting is controlled by a jumper or a
switch. On other internal SCSI devices you must
physically remove or install resistor module(s). On
most external SCSI devices, a terminating plug (a
resistor pack embedded in a small plug) is installed
or removed to control termination.
4
AHA-2940W
Termination
Low High
ON ON
ON ON
OFF OFF
ON ON
OFF ON
OFF ON