Scsi Controller - Siemens SIMATIC Rack PC 840 Manual

Controller
8.1

SCSI Controller

Overview
SCSI stands for Small Computer System Interface.
The SCSI controller (host adapter) acts as an interface between the internal bus
(PCI bus) and devices with an SCSI interface, called SCSI devices in the rest of
this document.
Every SCSI device, including the SCSI controller, has an SCSI bus address which
is its ID. Each ID is unique to that particular device. This description tells you how
to set up and display IDs.
The SCSI controller is a PCI module which uses PCI bus master technology. This
means that the controller can transfer data to and from the PC's working memory
to the SCSI device quickly and without any help from the CPU (Central Processing
Unit).
Your SCSI device documentation tells you how to install and operate your SCSI
device.
Setting SCSI Addresses (IDs)
Each SCSI device that is connected to the SCSI controller must be given its own
address (ID 0 to ID 15).
The SCSI controller supports standard SCSI and ultrawide SCSI. With standard
SCSI, devices with ID 0 to ID 7 can be connected; with ultrawide SCSI, devices
with ID 0 to 15 can be connected. ID 15 has the highest priority. The controller
itself has ID 7, so it can support both types of SCSI.
• Make sure that each SCSI device has its own unique SCSI ID.
More details about setting the SCSI address are contained in your SCSI device
documentation.
Connecting SCSI Devices
SCSI devices and the SCSI controller are connected via a common bus (SCSI
bus).
Termination (terminal resistance) must be enabled (or installed) on the SCSI
devices connected at the ends of the SCSI cable. Termination must be disabled (or
removed) on all other SCSI devices.
Your SCSI device documentation tells you how to enable or disable termination on
SCSI devices that have been added on later.
• Make sure that termination is properly installed.
• Connect the devices via the SCSI cable to the SCSI connector on the system
module.
• The SCSI controller terminator must be disabled when you connect devices
with the external SCSI bus.
8-2
SIMATIC Rack PC 840 Manual
A5E00104826-03