Connecting Scsi Devices - Adaptec AHA-3940U Installation Manual

5

Connecting SCSI Devices

Caution:
AHA-3940U/3940UW/3940UWD
host adapters support only single-ended SCSI
devices. Do not connect differential SCSI
devices, because they may damage the host
adapter. Read the SCSI device documenta-
tion if you are not sure whether the device is
single-ended or differential.
Connecting Cables
SCSI devices are cabled together in a single,
connected series called the SCSI bus. SCSI cables
must run sequentially from one device to the next,
with no branching.
1
Lay out the cables and find the pin-1 element of
each cable and device connector.
On internal cables, pin 1 is usually marked with a
contrasting color on one edge of the ribbon cable,
and a small triangle or number 1 marks pin 1 on
the SCSI connector. External cables 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 device(s), using the internal and/or external
connector(s). Be sure to maintain correct pin-1 ori-
entation throughout the bus for each channel. If
you are connecting 8-bit SCSI devices to either
channel of an AHA-3940UW or AHA-3940UWD,
you will need 68-pin-to-50-pin converters. Refer
to the User's Guide for detailed information.
On the AHA-3940U/3940UW host adapters, SCSI
Channel A has one external and one internal
connector. These are labeled J5 and J1, respec-
tively, in the diagrams on pages 1 and 2. SCSI
Channel B has an internal connector only (J2).
The AHA-3940UWD host adapter has two
external connectors (J7 and J5) and two internal
connectors (J1 and J2) — one of each type of
connector for each channel.
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AHA-3940U/3940UW/3940UWD Installation Guide
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Part Number: 511040-00, Rev. B
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Print Spec Number: 494568-00
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Current Date: 11/14/96
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ECN Date:11/18/96
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