Connectors; Connection Considerations - ATTO Technology UL3D Installation And Operation Manual

Connectors

ATTO ExpressPCI UL3S/UL3S-66:
standard 68-pin "P" (16-bit) cable connector for
internal device connections and one 68-pin "P"
(16-bit) VHDCI (Very High Density Cabled
Interconnect) cable connector for external device
connections.
ATTO ExpressPCI UL3D/UL3D-66:
standard 68-pin "P" (16-bit) cable connectors for
internal device connections and two 68-pin "P"
(16-bit) VHDCI (Very High Density Cabled
Interconnect) cable connectors for external device
connections.

Connection considerations

If using a combination of Wide 16-bit devices and
Narrow 8-bit devices on the same connector,
Wide devices must be connected first (closest to
the connector), followed by the Narrow devices.
Please refer to the documentation you received
Termination
The SCSI bus is a chain of SCSI devices. The
devices at both ends of any SCSI chain must be
terminated for the SCSI bus to function correctly.
A SCSI device chain can be configured in three
different ways: internal, external and an
internal/external SCSI device chain.
The ATTO ExpressPCI SCSI adapter is a SCSI
device and may require termination depending
upon the configuration. Be sure to use the correct
terminator. Single-Ended, Low Voltage
Differential and Differential SCSI busses use
different types of terminators that should not be
mixed.
Single-Ended and LVD signaling
ExpressPCI Ultra3 SCSI host adapter supports
two types of SCSI signaling: Low Voltage
Differential (LVD) and Single-Ended. Ultra2 and
Ultra3 SCSI require LVD signaling for optimal
performance. UltraSCSI and slower devices use
Single-Ended signaling. Devices on the same
SCSI bus must use the same signaling, either LVD
or Single-Ended.
with your SCSI devices to determine if your
device is Wide or Narrow.
one industry
Exhibit 3.1-2 Several types of internal and external
cable connectors.
two industry
Terminators
SCSI host adapters must match the SCSI bus
signal. When using only LVD devices an LVD
terminator should be used. A Single-Ended
terminator with LVD devices usually works, but
all devices will be limited to Ultra SCSI speeds,
instead of Ultra2 or Ultra3 speeds. Single-Ended
devices require a Single-Ended terminator. If you
use an LVD terminator with Single-Ended
devices, the system may hang or devices will not
be seen on the SCSI bus. Some termination
manufacturers provide terminators which
automatically sense Single-Ended or LVD
termination.
The
Internal and external termination
terminators should be attached to the last external
device in the SCSI chain. Be careful not to provide
any other termination on the external SCSI chain.
(Extra termination will cause a loss in signal
quality.) The last device on an internal SCSI chain
should also be terminated. Many Single-Ended
Ultra SCSI and earlier devices provide a jumper
setting for applying termination, in which case the
last device on the internal cable should have a
SCSI terminators used with Ultra3
External
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