4
AHA-2940/2940W Installation Guide
Part Number: 510881-00, Rev. A
Print Spec Number: 493890-00
Current Date: 7/5/95
ECN Date: 7/11/95
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
A
A
A
A
A
A
A
A
A
A
A
A
A
A
■
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.
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.
AHA-2940W
Termination
Devices Connected to AHA-2940W
Low
High
68-pin internal connector only
ON
ON
68-pin external connector only
ON
ON
68-pin internal and 68-pin external connectors
OFF
OFF
50-pin internal connector only
ON
ON
50-pin and 68-pin internal connectors
OFF
ON
50-pin internal and 68-pin external connectors
OFF
ON