Termination; Scsi Addressing (Id) - Adaptec AHA-1740A Technical Reference Manual

EISA-to-Fast SCSI Host Adapter
Each EISA system is shipped with a configuration utility to assign parameters such
as port addresses and interrupt priorities to boards installed in the system. This
must be used to identify and configure the board in your system. The details vary
from vendor to vendor. Refer to the system documentation for details.
The Adaptec AHA-1740A/1742A/1744 32-bit EISA bus-to-SCSI bus host adapter has
been designed to operate as shipped in the majority of EISA class computers. A board
direct from the factory is normally shipped with the ASW-C174 Configuration
Utility. This utility permits parameters associated with the board and the SCSI bus
to be set up through the system keyboard and CRT.

Termination

The SCSI bus must be terminated correctly to assure proper operation. The first and
last physical SCSI devices on the SCSI cable must have terminators installed. All
other SCSI devices must have terminators removed. The host adapter is shipped
with terminators which are three Serial In-line Packages (SIPs) located near the 50-
pin internal SCSI flat ribbon connector at locations RN3, RN4, and RN5. The inter-
nal and external connectors connect to the same SCSI bus, so both internal and
external cabling must be considered in determining where terminators are installed.
If only one cable (either internal or external) is connected to the host adapter, the ter-
minators must remain installed in the host adapter. Terminators must also be in-
stalled on the device at the farthest end of the cable from the host adapter.
Terminators must be removed from all other attached SCSI devices.
If both an internal and external cable are connected to the host adapter, remove the
terminators on the host adapter and install terminators on the devices at the farthest
end of each cable. Terminators must be removed from all devices except the device at
the end of each cable. The instruction manuals for each SCSI device will indicate how
the terminators can be removed or replaced.

SCSI Addressing (ID)

The SCSI target address for each SCSI device to be attached must be selected by set-
ting the proper jumpers or switches on the device in Standard Mode. The SCSI device
that is to be used as the boot disk must have a SCSI address of zero. In Enhanced
Mode, you can boot to any SCSI ID. Refer to the section titled Enhanced Mode SCSI
Configuration for further details.
SCSI Addresses 0 and 1 should be reserved for SCSI hard disk drives. Each installed
peripheral must have a different SCSI address. The host adapter's default SCSI ID is
7. Duplicate SCSI addresses will cause errors that are extremely difficult to identify.
Any jumpers that control operating modes must also be properly set. If there is a
jumper that enables synchronous transfer and/or synchronous negotiation, the
jumper should be set to enable synchronous.
Installation
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