5
AHA-2840A/2842A Installation Guide
Part Number: 510590-00, Rev B
Print Spec Number: 492663-00
Current Date: 5/9/96
ECN Date: 6/3/96
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Caution:
AHA-2840A/2842A host adapters
support only single-ended SCSI devices.
Differential SCSI devices may be damaged if
connected to the host adapter. The periph-
eral documentation will tell you whether the
device is single-ended or differential.
1
Lay out the cables and find the pin-1 element of
each cable and peripheral connector.
On internal cables, pin 1 is usually marked with a
contrasting color on one edge of the ribbon cable,
and a small triangle marks pin 1 on the SCSI con-
nector. External cable connectors can only be
plugged-in one way, so pin-1 orientation is
automatic.
2
Attach the SCSI cable(s) to the host adapter and
the peripheral(s), using the internal and/or exter-
nal connector(s).
3
Be sure to maintain correct pin-1 orientation
throughout the bus. The AHA-2840A/2842A uses
a 50-pin high-density external connector, and a
50-pin flat ribbon-type internal connector.
4
If you are installing an AHA-2842A and you are
using the onboard floppy controller, connect the
34-pin ribbon cable to the onboard floppy connec-
tor. Be sure to maintain pin-1 orientation, as
described earlier.
Terminating the SCSI Bus Cable
The last physical SCSI device on either end of the
SCSI bus must have a set of resistors called termina-
tors. Terminators must be removed from, or dis-
abled on, all other devices on the SCSI bus.
The AHA-2840A/2842A and most SCSI peripherals
have built-in terminators that can be enabled or dis-
abled. Terminate only the devices at each end of the
SCSI bus.
Terminating the Host Adapter
Termination is enabled by default on AHA-2840A/
2842A host adapters. You must disable host adapter
