Connection Considerations; Termination - ATTO Technology ATTO ExpressPCI Ultra/WIDE SCSI Host Adapters Express PCI PSC: Single-Channel Single-Ended Ultra/WIDE ExpressPCI DC: Dual-Channe Installation And Operation Manual

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
Exhibit 3.1-2 Several types of internal and external cable connectors.

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 buses use
different types of terminators that should not be
mixed.
Single-Ended ATTO ExpressPCI PSC/DC
incorporates advanced termination circuitry to
automatically configure its own termination.
Exhibit 3.1-3 Two LEDs on the top edge of the ATTO
ExpressPCI PSC/DC provide feedback on its automatic
termination setting.
LED1 LED 2
(Low Term) (High Term)
On On
Off Off
Off On
You should not have to manually adjust the
termination of your adapter unless you a narrow
(8 bit) device attached to the external port AND a
ATTO ExpressPCI-PSC
termination
All 16 data bits terminated
No termination
Upper 8 bits terminated
the connector), followed by the Narrow devices.
Please refer to the documentation you received
with your SCSI devices to determine if your
device is Wide or Narrow.
wide (16 bit) device attached to the internal port
of your ATTO ExpressPCI PSC/DC OR if you
attached a narrow (8 bit) device to the internal
WIDE (16 bit) connector and a WIDE (16 bit)
device to the external port. You must manually
terminate the adapter using ATTO ExpressPCI
Utilities program with the termination option set
to Upper.
The ATTO ExpressPCI SCSI adapter only
controls its own termination. You must terminate
the last device of both the internal SCSI chain and
the external SCSI chain.
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