ATTO Technology operation manual Cables, termination, Connection considerations, Termination

Connection considerations	the connector), followed by the Narrow devices.
If using a combination of Wide 16-bit devices and	Please refer to the documentation you received
Narrow 8-bit devices on the same connector,	with your SCSI devices to determine if your
Wide devices must be connected first (closest to	device is Wide or Narrow.

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

Cables,

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	ATTO ExpressPCI-PSC
(Low Term)	(High Term)	termination
On	On	All 16 data bits terminated
Off	Off	No termination
Off	On	Upper 8 bits terminated

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

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.

termination

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