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Document:	StorageWorks Solutions DWZZA 8-Bit SCSI Bus Converter User's Guide
Order Number:	EK-DWZZA-UG
Revision:	A01
Pages:	24
Original Filename:

OCR Text

Solutions
DWZZA 8-Bit SCSI Bus Converter
Users Guide
Order Number EK–DWZZA–UG. A01
This guide describes the procedures for installing and configuring both the table top
(DWZZA–AA) and the StorageWorks (DWZZA–VA) 8-bit SCSI bus converters.

Digital Equipment Corporation
Maynard Massachusetts

April 1995
While Digital believes the information included in this publication is correct as of the date of
publication, it is subject to change without notice.
Note
Only the self-powered table top model, the DWZZA–AA, is FCC Class B certified.
The DWZZA–VW converter does not require separate FCC certification but is
certified as part the StorageWorks subsystem in which it is installed.
FCC ID: A09-DWZZA
NOTE: This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to Part 15 of the FCC rules. These limits are designed to provide
reasonable protection against harmful interference in a residential installation.
Any changes or modifications made to this equipment may void the user's authority to operate
this equipment.
This equipment generates, uses, and can radiate radio frequency energy and, if not installed
and used in accordance with the instructions, may cause harmful interference to radio
communications. However, there is no guarantee that interference will not occur in a
particular installation. If this equipment does cause harmful interference to radio or television
reception, which can be determined by turning the equipment off and on, the user is
encouraged to try to correct the interference by one or more of the following measures:

•
•
•
•

Reorient or relocate the receiving antenna
Increase the separation between the equipment and receiver
Connect the equipment into an outlet on a circuit different from that to which the receiver
is connected
Consult the dealer or an experienced radio/TV technician for help

This equipment requires the use of shielded SCSI cables such as the Digital Equipment
Corporation BN21K-series, BN21L-series, BN21R-series, or BN23G-series.
Copyright © Digital Equipment Corporation 1995
Printed in the United States of America.
All rights reserved.
StorageWorks and the DIGITAL logo are trademarks of Digital Equipment Corporation.
This document was prepared using Microsoft Word for Windows, Version 6.0.

Contents
Chapter 1 Introducing the 8-Bit SCSI Bus Converters
1.1 SCSI Bus Converter Functions .............................................................................................1–1
1.2 Product Descriptions ............................................................................................................1–2
1.2.1 SBB Shelf Converter ...........................................................................................1–2
1.2.2 Table Top Converter............................................................................................1–2
1.2.3 SCSI Bus Components.........................................................................................1–3
1.3 Product Specifications..........................................................................................................1–4

Chapter 2 Using an 8-Bit SCSI Bus Converter
2.1 SCSI Buses ..........................................................................................................................2–2
2.2 Selecting the SCSI Cables ....................................................................................................2–3
2.3 Determining the Configuration ............................................................................................2–4
2.3.1 End-Bus Configuration........................................................................................2–4
2.3.2 Mid-Bus Configuration........................................................................................2–6
2.4 Setting the Bus Termination.................................................................................................2–7
2.4.1 Mid-Bus SCSI Bus Converter ..............................................................................2–8
2.4.2 End-Bus SCSI Bus Converter Terminators ........................................................2–10

Glossary
Figures
Figure 1–1 SBB Shelf DWZZA–VA SCSI Bus Converter .........................................................1–2
Figure 1–2 DWZZA–AA SCSI Bus Converter—Differential Connector....................................1–3
Figure 1–3 DWZZA–AA SCSI Bus Converter—Single-Ended Connector.................................1–3
Figure 2–1 BN21K-Series Cable Connectors.............................................................................2–3
Figure 2–2 BN21L-Series Cable Connectors .............................................................................2–3
Figure 2–3 BN21R-Series Cable Connectors .............................................................................2–3
Figure 2–4 BN23G-Series Cable Connectors.............................................................................2–3
Figure 2–5 Typical End-Bus Configurations .............................................................................2–5
Figure 2–6 Typical Mid-Bus Converter Configuration ..............................................................2–6
Figure 2–7 H885–AA Trilink Connector...................................................................................2–8
Figure 2–8 DWZZA Mid-Bus Terminators ...............................................................................2–9
Figure 2–9 DWZZA–VA End-Bus Bus Terminators ...............................................................2–11

Tables
Table 1–1 SCSI Bus Converter Functional Specifications..........................................................1–4
Table 2–1 SCSI Buses and Cables.............................................................................................2–2
Table 2–2 Connector Compatibility...........................................................................................2–3

iii

Preface
The StorageWorks Solutions DWZZA SCSI Bus Converter describes the purpose, function,
operation, and use of the 8-bit SCSI bus converter. This SCSI bus converter extends the
length of the bus between controllers and the SCSI devices.

Intended Audience
This publication is for use by customers and Digital™ employees responsible for configuring,
installing, and maintaining the StorageWorks subsystem and its components.

Documentation Conventions
The following conventions are used in this manual:
boldface type

Boldface type indicates the first instance of terms being defined in text,
in the glossary, or both.

italic type

Italic type indicates emphasis and complete manual titles. In the
glossary, italic type indicates a cross–reference.

Structure
This manual is organized as follows:
Chapter 1
Introducing the DWZZA

This chapter is an overview of the SCSI bus converters.

Chapter 2
Using a DWZZA

This chapter describes the procedures for configuring a SCSI
bus using a SCSI bus converter.

Glossary

Related Documents
The following are StorageWorks documents relative to this product:
Document Title
StorageWorks Solutions Configuration Guide
StorageWorks Solutions Shelf and SBB User's Guide

Order Number
EK–BA350–CG
EK–BA350–UG

1
Introducing the 8-bit
SCSI Bus Converters
The DWZZA-series SCSI bus converters (converter) are SCSI–2 compliant single-ended
SCSI to differential SCSI 8-bit converters capable of data transfer rates of up to 10 mega bytes
per second (10 MB/s). This chapter describes the following converters:

•
•

The DWZZA–AA is a stand alone self powered, table top unit.
The DWZZA–VA is a StorageWorks building block (SBB) carrier for installation in an 8bit SBB shelf.
Note
The discussion of the DWZZA-series SCSI bus converters in this guide addresses
the models, applications, cables, and configurations compatible with the
StorageWorks building block (SBB) shelves. The capabilities and use of these
converters in other environments or with other SCSI systems are not within the
scope of this guide.

1.1 SCSI Bus Converter Functions
All the SBB shelves are either 8-bit or 16-bit single-ended, physical buses. Some controllers
and hosts use differential buses and others use a single-ended bus. Single-ended and
differential physical buses are not compatible. The SCSI protocol disables both buses when
they are connected. However, by using a SCSI bus converter you can accomplish the
following:

•
•

Connect a differential physical bus to a single-ended physical bus
Extend the maximum length of a SCSI bus

The SCSI bus converter internal logical bus establishes compatibility between the differential
and singled-ended physical buses and connects them as a single logical bus.
These converters may be installed alone or in combination and can be configured to operate in
either the end-bus or the mid-bus location simply by either installing or removing bus
terminators.

Introducing the 16-Bit SCSI Bus Converters 1–1

1.2 Product Descriptions
There are three types of DWZZA SCSI bus converters—the DWZZA–AA, the DWZZA–MA,
and the DWZZA–VA. The two types used with the StorageWorks product line are the SBB
version, the DWZZA–VA and the table top version, the DWZZA–AA. As described in
Chapter 2, these converters can be installed in either the end-bus or the mid-bus position.
The DWZZA–MA version has neither an enclosure nor a power source and can only be
installed as an option. It use is described in the option documentation.

1.2.1 SBB Shelf Converter
The DWZZA–VA is an SBB shelf converter installed in slot 0 of an 8-bit shelf, such as a
BA350–SB. The 8-bit differential cable connector is a 68-pin, high-density female connector.
The 8-bit single-ended output connector is a 96-pin DIN connector that mates with the shelf
backplane.
Figure 1–1 SBB Shelf DWZZA–VA SCSI Bus Converter

CXO-4543A-MC

CXO-4544A-MC

1.2.2 Table Top Converter
The DWZZA–AA is a table top converter with a self-contained power supply. The 68-pin
high-density female connector is used for the differential SCSI bus (see Figure 1–2). The
50-pin single-ended low-density connector is used for the single-ended SCSI bus (see
Figure 1–3).

1–2 Introducing the 8-Bit SCSI Bus Converters

Figure 1–2 DWZZA–AA SCSI Bus Converter—Differential Connector

DIFFERENTIAL
CONNECTOR

CXO-4639A-MC

Figure 1–3 DWZZA–AA SCSI Bus Converter—Single-Ended Connector

50-PIN
LOW-DENSITY
CONNECTOR
I
O

AC
RECEPTACLE
POWER
SWITCH

CXO-4720A-MC

1.2.3 SCSI Bus Components
To install a SCSI bus converter you need both a SCSI ”A” and a SCSI ”P” cable (see Section
2.2). Please refer to the StorageWorks Solutions Configuration Guide for a complete list of
the available cables. For a mid-bus configuration you will need an H885–AA trilink
connector (see Figure 2–7).

Introducing the 16-Bit SCSI Bus Converters 1–3

1.3 Product Specifications
Table 1–1 lists the functional specifications for the table top (DWZZA–AA) and SBB shelf
(DWZZA–VA) SCSI bus converters.
Table 1–1 SCSI Bus Converter Functional Specifications
Features
SCSI ID and SCSI Addresses
Overload Protection
DTERMPOWER
STERMPOWER
Shielding
Enclosure
Connectors
Power-Up Reset

SCSI Bus Reset

Single-Ended SCSI Bus Length
Slow (5 MB/s)
Fast (10 MB/s)
Differential SCSI Bus Length
Data Timing

Design
Cable Fault
Glitch Elimination

No SCSI IDs (device addresses) are consumed by the
converter.
1.5 A self-resetting thermal fuse
1.5 A self-resetting thermal fuse
Shielded for ESD, EMI, and safety requirements
Shielded for ESD, EMI, and safety requirements
Automatically clears
• Initiator detection circuit
• Target detection circuit
• BSY glitch filter
Automatically clears
• Initiator detection circuit
• Target detection circuit
• BSY glitch filter
(See Table 2–1 for detailed specifications)
6 meters (19.7 feet)
3 Meters (9.8 feet)
25 meters (82 feet)
The relationship between the data and the control
signals is brought to SCSI compatibility before
transmission to the other SCSI bus.
High reliability SMT
DIFFSENSE support
• 100% glitch free operation during power-up
• BUSY GLITCH trap eliminates cable length
constraint due to wired-OR glitches on the BSY
line

Termination
• End-bus terminators installed and enabled at the factory.
• Remove or disable terminators for mid-bus operation.
Singled-ended
User selectable 8-bit active termination.
Remove the jumper for mid-bus operation.
Differential
Five 14-pin SIP resistors.
Remove SIPs for mid-bus operation
TERMPOWER
Supplied to both buses.
Service
• The user can install (enable) or remove (disable) the bus termination.
• Contact Digital service personnel for all other service.

1–4 Introducing the 16-Bit SCSI Bus Converters

Table 1–1 SCSI Bus Converter Functional Specifications (Continued)
Configuration Rules
The maximum number of DWZZAs between any two devices is 2.
Agency Approvals
UL, CSA, FCC Class B, TUV
Environmental Specifications
Relative Humidity
10% to 85% non-condensing
Operating Temperature
10°C to 40°C (50°F to 104°F)
Storage Temperature (non-operating) –40°C to 66°C (–40°F to 151°F)
Power Requirements
Input Voltage
+5.0 V dc, ±0.25 V dc
Input Current
Electronics
3.1 Amps
Terminators
0 to 3.0 Amps (in addition to electronics)
TERMPOWER
Supplied to both buses
SCSI Connectors and Cables
Single-Ended
Surface mount unitized connector includes:
• Standard 4-pin power connector
• 50-pin, female, low-density SCSI ”A” connector
Differential
Board mounted 68-pin, female, high-density
SCSI ”P” connector
• BN21R-series and BN23G-series shielded
Cables
SCSI ”A” cables
• BN21K-series and BN21L-series shielded
SCSI ”P” cables

Introducing the 16-Bit SCSI Bus Converters 1–5

2
Using an 8-bit
SCSI Bus Converter
This chapter discusses how to effectively use a converter by selecting configurations, cables,
terminating the buses, and installing the converter. Complete the following procedures in the
specified sequence to install and use a converter:

•
•
•
•

Determine the SCSI bus type, speed, and maximum physical length (see Section 2.1).
Determine the optimum configuration for your system (see Section 2.3).
Select the SCSI bus cables (see Section 2.2).
Set the bus terminations on the converter (see Section 2.4).
Note
In this section, the term controller means any one of the following SCSI devices:
(1) a controller, (2) a host computer, or (3) an adapter.

Using a 16-bit SCSI Bus Converter 2–1

2.1 SCSI Buses
The SCSI bus length is the total length from the bus terminator on the controller to the
terminator at the other end of the bus. For a basic configuration, this is the distance from the
controller terminator to the shelf terminator.
Table 2–1 is a synopsis of the SCSI buses supported by the 8-bit converter organized by bus
type (single-ended or differential). This table includes the following information:

•
•
•
•

Bus speed (fast or slow)
Data transfers per seconds expressed either in mega bytes (MB/s) or mega transfers
(MT/s)
The maximum length of each bus in meters (M) and feet (ft)
The maximum length SCSI ”A” and SCSI ”P” cable for each.
Note
Changes in differential bus speed or width only affect the data transmission rate.
The maximum bus length and cable length remains constant.

Table 2–1 SCSI Buses and Cables
Buses
Transfer Rate
Width Speed
Type
MT/s* MB/s
SCSI ”A” Cables (Use only with DWZZA–AA)

Bus Length
Meters
Feet

8-bit

Fast

Single-ended

9.8

8-bit

Slow

Single-ended

19.7

Recommended Cable
Order No. Meters
Feet
BN21R–02
BN23G–02
BN21R–05
BN23G–05

6.6

16.4

BN21K–23
BN21L–23
BN21K–23
BN21L–23

75.5

SCSI ”P” Cables
8-bit

Fast

Differential

8-bit

Slow

Differential

Note
MT/s (megatransfers per second) is the repetitive rate at which words of data are
transferred across a bus. The number of megabytes per second (MB/s) is
determined by the bus width (8-, 16-, or 32-bit) and the number of bytes per word
(1, 2, or 4, respectively).
The maximum bus length and maximum cable length are not the same.

•

The bus length is measured from the controller terminator to the SBB shelf terminator
and includes the SCSI cables.

Megatransfers per second

2–2 Using a 16-bit SCSI Bus Converter

•

The maximum cable length is the longest cable length that can be used without exceeding
the maximum bus length. For example, you cannot use a 25 m (82 ft) cable when the
maximum bus length is 25 m. You must allow for the SBB shelf bus length. Therefore,
the maximum length cable you should use is 23 m (75.5 ft).

2.2 Selecting the SCSI Cables
The StorageWorks Solutions Configuration Guide describes SCSI cables in detail.
When selecting a cable you must consider the cable connector clearance. Be sure to determine
the type connector compatible with the controller connector. In some cases you must use a
right-angle connector because there is not enough clearance to use a straight connector. The
following are the cable connector requirements:
Table 2–2 Connector Compatibility
Connector Type
Component

68-Pin

50-Pin

SBB shelf converter (DWZZA–VA)

Right-angle

N/A

Table top converter (DWZZA–AA)

Right-angle or straight

Host, adapter, or controller

Check the controller documentation to determine
requirements

Right-angle or straight

The recommended SCSI ”P” cables are the BN21K-series (see Figure 1–1) and the
BN21L-series (see Figure 2–2). The recommended SCSI ”A” cables are the BN21R-series
(see Figure 2–3) and the BN23G-series (see Figure 2–4).
Figure 2–1 BN21K-Series Cable Connectors

Figure 2–2 BN21L-Series Cable Connectors

CXO-4172A-MC_R

CXO-4171A-MC_R

Figure 2–3 BN21R-Series Cable Connectors

StorageWorks
CONNECTOR

Figure 2–4 BN23G-Series Cable Connectors

CXO-4166A-MC_R

StorageWorks
CONNECTOR
CXO-4167A-MC_R

Using a 16-bit SCSI Bus Converter 2–3

2.3 Determining the Configuration
The manner in which you configure the SCSI bus converter is based upon the SCSI controller
and what you are planning to accomplish. There following are the two basic configurations
for a converter:

•
•

The end-bus configuration (see Section 2.3.1)
The mid-bus configuration (see Section 2.3.2)
CAUTION
Regardless of the configuration used, end-bus or mid-bus, you cannot separate the
controller and the devices with more than two converters in series. For example,
One table top and one SBB shelf converter in series.

2.3.1 End-Bus Configuration
The end-bus configurations shown in Figure 2–5 terminates all cables in the converter, the
shelf, and in the controller. This effectively creates two physical buses, one between the
converter and the controller; the other between the converter and the SBB shelf.
Note
Both the differential and the single-ended SCSI bus terminators are
factory-installed. You do not need to change the termination to operate the
converter in the end-bus position.
Figure 2–5 shows the three basic end-bus configurations:
Note
Devices addresses 0 through 15 are valid when using a 16-bit controller. When
using an 8-bit controller the valid device addresses are 0 through 6.

•
•
•

Single-Ended Controller to SBB Shelf
All StorageWorks SBB shelves are single-ended SCSI buses. When the single-ended is
operating at 5 MB/s (slow) the maximum SCSI bus length is 6 m (19.7 ft).
Differential Controller to SBB Shelf
This configuration requires an SBB shelf converter in Slot 0. Connect the controller to
the SBB shelf converter with a SCSI ”P” cable.
Single-Ended Controller to SBB Shelf—Extended Length
This configuration requires two SCSI bus converters—a table top models and an SBB
shelf converter (see Figure 2–5). Depending upon the bus speed (fast or slow) the total
bus length could be between 31 m (101.8 ft) or 37 m (121.4 ft).
−

Install the –VA model in SBB shelf slot 0.

−

Connect the controller to the table top converter single-ended connector using a
SCSI ”P” cable.

−

Connect the table top converter differential connector to the SBB shelf converter with
a SCSI ”P” cable.

2–4 Using a 16-bit SCSI Bus Converter

Note
When using an 8-bit single-ended controller the valid shelf device addresses are 0
through 6.

Figure 2–5 Typical End-Bus Configurations
CONFIGURATION 1

SINGLEENDED
SCSI
CONTROLLER

8-BIT
SBB
SHELF

SCSI "A"
CABLE
JA-1

CONFIGURATION 2

8-BIT
SBB
SHELF

DIFFERENTIAL
SCSI
CONTROLLER
SCSI "P" CABLE

SLOT 0

DWZZA-VA

JA-1

CONFIGURATION 3

8-BIT
SBB
SHELF

SINGLEENDED
SCSI
CONTROLLER

SLOT 0
DWZZA-VA

DWZZA-AA
SCSI "A"
CABLE

SCSI "P"
CABLE
JA-1
CXO-4721A-MC

Using a 16-bit SCSI Bus Converter 2–5

2.3.2 Mid-Bus Configuration
The typical mid-bus configuration shown in Figure 2–6 creates the following three buses:

•
•
•

A 25 m (82 ft) differential bus from the controller through the tri-link connector on the
SBB shelf 1 converter to SBB shelf 2 converter.
A single-ended bus on SBB shelf 1
A single-ended bus on SBB shelf 2

To create this shelf requires that you remove the differential termination from SBB shelf 1
converter using the procedure Section 2.4.1. The single-ended termination would remain in
place. The termination in SBB shelf 2 converter would remain in the end-bus configuration.
Note that the total length of the differential bus remains at 25 m (82 ft). Therefore, for proper
operation the total length of the SCSI ”P” cables must be less than 25 m.
Figure 2–6 Typical Mid-Bus Converter Configuration

DIFFERENTIAL
SCSI HOST

H885A
TRILINK
CONNECTOR

BA350
SBB
SHELF
DWZZA-VA

MID-BUS
POSITION

DWZZA-VA

END-BUS
POSITION
CXO-3871A-MC

2–6 Using a 16-bit SCSI Bus Converter

2.4 Setting the Bus Termination
All SCSI buses are terminated at the physical ends of the bus. This is true even when using a
DWZZA SCSI bus converter. Both DWZZA SCSI bus converters supply terminator power
(TERMPOWER) to the SCSI terminators. TERMPOWER is electrical current that is limited
by self-resetting fuses.
The following sections describe the procedures for configuring a DWZZA SCSI bus converter
for either a mid-bus (see Section 2.4.1) or end-bus (see Section 2.4.2) operation.
CAUTION
To prevent SCSI bus malfunction, do not remove the DWZZA SCSI bus converter
or disconnect the SCSI cable when power is on.

Using a 16-bit SCSI Bus Converter 2–7

2.4.1 Mid-Bus SCSI Bus Converter
Use an H885-AA trilink connector (see Figure 2–7), to place the converter in the mid-bus
position as shown in Figure 2–6. Use the following procedure to configure the differential
connector for mid-bus operation:
Figure 2–7 H885–AA Trilink Connector

REAR VIEW

FRONT VIEW
CXO-3851A-MC

CAUTION
Do not attempt the following procedure without taking proper precautions against
electrostatic discharge (ESD). Wear an ESD grounding wrist strap whenever you
remove the cover from any enclosure or device.
1.

Turn off the power and remove the input power cable.

Disconnect the SCSI cables.

Remove either the SBB bezel and cover, or the table top converter cover.
CAUTION
The tri-link connector is always installed on the converter SCSI bus input
connector. Remove the bus termination only for the input connector. Do not
remove the termination for the output connector.

Remove the five differential bus resistor SIPs (see Figure 2–8).
Note
The converters in the end-bus position are configured as shown in Figure 2–9.

Replace the SBB converter cover and bezel, or the table top converter cover.

Install the trilink connector on the differential connector.

2–8 Using a 16-bit SCSI Bus Converter

Connect the input SCSI ”P” cable from the controller or the table top converter to the
trilink connector (see Figure 2–6).

Connect a SCSI-P cable from the trilink connector to the input connector on the second
converter.

Make sure that the differential bus is terminated in the last converter on the bus (refer to
Section 2.4.2).

10. Digital recommends that you label the converters with the status of both the differential
terminator and the single-ended terminator, as either IN or OUT.
11. Install the SBB converter.
12. Connect the input power cable and apply power to the shelf.
13. Observe the system to determine if the SCSI bus and devices are functioning properly.
Figure 2–8 DWZZA Mid-Bus Terminators
SSB SHELF CONVERTER
DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

SINGLE-ENDED
SCSI-2 TERMINATION

J2
SINGLE-ENDED
CONNECTOR

DIFFERENTIAL
CONNECTOR

TABLE TOP CONVERTER
SINGLE-ENDED
SCSI-2 TERMINATION

DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

J2
SINGLE-ENDED
CONNECTOR
DIFFERENTIAL
CONNECTOR

CXO-4723A-MC

Using a 16-bit SCSI Bus Converter 2–9

2.4.2 End-Bus SCSI Bus Converter Terminators
Use the following procedure to configure the converter termination from a mid-bus to an
end-bus position (see Figure 2–5 and Figure 2–6).
CAUTION
Do not attempt the following procedure without taking proper precautions against
electrostatic discharge (ESD). Wear an ESD grounding wrist strap whenever you
remove the cover from any enclosure or device.

Note
Both the differential and the single-ended SCSI bus terminators are
factory-installed. You do not need to change the termination to operate the
converter in the end-bus position.
1.

Turn off the power and remove the input power cable.

Disconnect the SCSI cables.

Remove either the SBB converter bezel and cover, or the table top converter cover.
CAUTION
To prevent damage, remove the SBB bezel only as required and use minimal
pressure used when pushing down on the mounting tabs.

To terminate the single-ended input SCSI bus, install jumper J2 (see Figure 2–9).

To terminate the differential input SCSI bus install the five resistor single-inline-packages
(SIPs).

Replace the SBB converter cover and bezel, or replace the table top converter cover.

Digital recommends that you label the converters with the status of both the differential
terminator and the single-ended terminator, as either IN or OUT.

Install the SBB in the shelf.

Connect the SCSI ”P” cables.

10. Connect the input power cable and apply power.
11. Observe the system to determine if the SCSI bus and devices are functioning properly.

2–10 Using a 16-bit SCSI Bus Converter

Figure 2–9 DWZZA–VA End-Bus Bus Terminators
SSB SHELF CONVERTER
DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

SINGLE-ENDED
SCSI-2 TERMINATION

J2
SINGLE-ENDED
CONNECTOR

DIFFERENTIAL
CONNECTOR

TABLE TOP CONVERTER
SINGLE-ENDED
SCSI-2 TERMINATION

DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

J2
SINGLE-ENDED
CONNECTOR
DIFFERENTIAL
CONNECTOR

CXO-4724A-MC

Using a 16-bit SCSI Bus Converter 2–11

Glossary
adapter
See SCSI bus converter.
building block shelf
See SBB shelf.
controller
A hardware/firmware device that manages communications on behalf of host systems over the
SCSI bus to devices, such as the HSC-series, HSJ-series, and HSZ-series controllers.
Controllers typically differ by the type of interface to the host and provide functions beyond
what the devices support.
differential SCSI bus
A signal's level is determined by the potential difference between two wires. A differential bus
is more robust and less subject to electrical noise than is a single-ended bus.
DWZZA
A StorageWorks compatible 8-bit SCSI bus converter.
See SCSI bus converter.
electrostatic discharge
See ESD.
ESD
Electrostatic discharge is the discharge of a potentially harmful static electric voltage as a
result of improper grounding.
host
The primary or controlling computer or any such unit (in a multiple computer network) to
which storage is attached.
initiator
A SCSI device that requests another device on the but to perform an operation. Any device on
the bus can be an initiator or a target.
logical bus
A single-ended, physical bus connected to a differential, physical bus by a SCSI bus converter.
physical bus
Two SCSI terminators separated by cables, connectors, and/or the backplane circuitry.
SBB
StorageWorks building block. The basic building block of the StorageWorks product line.
Any device conforming to shelf mechanical and electrical standards installed in either a 3½inch or 5¼-inch carrier is considered to be an SBB, whether it is a storage device, a power
supply, or other device.

Glossary—1

SBB shelf
The common name for any StorageWorks shelf that contains only power supply and storage
SBBs.
SCSI
Small Computer System Interface. This ANSI interface defines the physical and electrical
parameters of a parallel I/O bus used to connect computers and devices. The StorageWorks
subsystem implementation uses SCSI–2 for the transfer of data.
SCSI bus converter
Sometimes referred to as an adapter. (1) A connecting device that permits the attachment of
accessories or provides the capability to mount or link units. (2) The device that connects a
differential SCSI bus to a single-ended SCSI bus.
SCSI device
A host computer adapter, a peripheral controller, or an intelligent peripheral that can be
attached to the SCSI bus.
SCSI device ID
The bit-significant, representation of the SCSI addressing referring to one of the signal lines
numbered 0 through 15. Also referred to as target ID. For example, SCSI device ID 1 would
be represented as 00001.
SCSI mid-bus position
The physical location of a controller or a device that the SCSI bus passes through enroute to
the controller or device that contains the SCSI bus termination.
SCSI–P cable
A 68-conductor (34 twisted pairs) cable used for differential bus connections.
single-ended SCSI bus
A bus in which each signal’s logic level is determined by the voltage of a single wire in
relation to ground.
Small Computer System Interface
See SCSI.
StorageWorks
The Digital set of enclosure products that allows customers to design and configure their own
storage subsystem. Components include power, packaging, and interconnections in a
StorageWorks shelf. SBBs and array controllers are integrated therein to form level
enclosures to house the shelves. Standard mounting devices for SBBs are also included.
StorageWorks building block
See SBB.
target
A SCSI device that performs an operation requested by an initiator. Any device on the bus
can be an initiator or a target.
target ID
See SCSI device ID.
termpower
Is an electrical current that is limited by self-resetting fuses.

2—Glossary