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Note:
You cannot attach cables and SCSI devices
to all three AHA-2944UW connectors.
Terminating SCSI Devices
Read the device’s documentation to determine how to
enable or disable termination on your SCSI device(s). On
most internal SCSI devices the termination setting is con-
trolled by a jumper or a switch. On other internal SCSI
devices you must physically remove or install resistor
modules. On most external SCSI devices, a terminating
plug (a resistor pack embedded in a small plug) is
installed or removed to control termination.
Termination in Multiple Computer
Configurations
If you are setting up your SCSI bus so that SCSI devices
are shared by host adapters in two different computers,
you can enable your host adapter to provide termination
power and enable termination even when one computer
is powered
OFF
. To do this, place a jumper shunt on
jumper J4 to enable termination and control on data 0-7;
place a jumper shunt on jumper J2 to enable termination
on upper data 8-15 for the powered down computer.
Note:
This manual feature will override the
SCSISelect setting for termination control.
Installing Differential SCSI Devices
Caution:
The AHA-2944UW host adapter sup-
ports only differential SCSI devices. Do not con-
nect single-ended SCSI devices, because they
may damage the host adapter. Read the SCSI
device documentation if you are not sure
whether the device is single-ended or
differential.
You can connect up to fifteen 16-bit Differential Ultra
Wide SCSI devices (internal or external) to the
AHA-2944UW. If you want to combine wide and non-
wide SCSI devices, you can connect up to seven 8-bit
internal devices and up to eight 16-bit Wide SCSI devices
(internal or external) to a single AHA-2944UW.
Choosing SCSI Cables
The cables required to connect SCSI devices are deter-
mined by the type of devices you are installing, as
described in the following table:
Adaptec sells high-quality internal and external SCSI
cables. If your reseller does not stock these cables, you
can order them directly from Adaptec. (The phone num-
ber is listed on page 11.)
Note:
To guarantee reliable operation of your
SCSI devices and host adapter, be sure the maxi-
mum combined lengths for internal and exter-
nal SCSI cables does not exceed 25 meters
(82 feet).
Connecting Internal SCSI Devices
If you are connecting internal SCSI devices, make sure
you have an internal SCSI cable with enough connectors
to accommodate all of your devices.
1
Prepare each SCSI device for installation; configure
the device SCSI ID and terminators (terminate the last
internal device attached to the cable). For instruc-
tions, see the device’s documentation as well as
Installing the Host Adapter and SCSI Devices on page 2
2
Install the SCSI device in your computer. Refer to
your computer and device documentation for
instructions.
3
Plug the connector at one end of the internal SCSI
cable into one of the host adapter’s internal SCSI
connectors.
Make sure the colored stripe on one side of the cable
is aligned with pin-1 of the host adapter’s connector.
Pin-1 of the connector is usually designated by a
small triangle (
▲
), or a “1” on the connector.
4
Plug the remaining cable connectors into the connec-
tors on the backs of other SCSI devices (if any).
Make sure the colored stripe on the cable is aligned
with pin-1 of the device’s connector.
SCSI Device Type
SCSI Cable type
8-bit Internal SCSI
50-pin internal
16-bit Internal Wide SCSI
68-pin internal
16-bit External Wide SCSI
68-pin external
