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Document:	StorageWorks Solutions DWZZx-Series SCSI Bus Converters User's Guide
Order Number:	EK-DWZZX-UG
Revision:	A01
Pages:	37
Original Filename:

OCR Text

StorageWorks™ Solutions
DWZZx–Series SCSI Bus Converters
User’s Guide
Order Number:

EK–DWZZX–UG. A01

This publication describes the StorageWorks 8- and 16-bit SCSI Bus Converters,
specifications, and replacement procedures.

Digital Equipment Corporation
Maynard, Massachusetts

February 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.
FCC ID: AO9-DWZZX
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
Copyright © Digital Equipment Corporation 1994, 1995
Printed in the United States of America.
All rights reserved.
StorageWorks, InfoServer, DECraid, HSC, RC, and the DIGITAL logo are trademarks of Digital
Equipment Corporation.
The postpaid READER'S COMMENTS card requests the user's critical evaluation to assist in preparing
future documentation.
This document was prepared using MicroSoft Word, Version 6.0.

Table of Contents
Preface
1 Introduction
1.1 StorageWorks DWZZx Components...................................................................... 1–1
1.2 DWZZx Bus Signal Converter Description ............................................................ 1–1

2 DWZZA Signal Converters
2.1 DWZZA Description ............................................................................................. 2–1
2.2 DWZZA Features and Functions............................................................................ 2–2
2.3 Installing DWZZA SCSI Bus Signal Converters .................................................... 2–2
2.4 SCSI Cables........................................................................................................... 2–6
2.5 Terminating SCSI Buses........................................................................................ 2–6
2.5.1 End-Bus SCSI Bus Signal Converter Terminators ........................................ 2–7
2.5.2 Mid-Bus SCSI Bus Signal Converter Terminators........................................ 2–8

3 DWZZB Signal Converters
3.1 DWZZB Description ............................................................................................. 3–1
3.2 DWZZB Features and Functions............................................................................ 3–2
3.3 Installing DWZZB SCSI Bus Signal Converters .................................................... 3–2
3.4 SCSI Cables........................................................................................................... 3–6
3.5 Terminating SCSI Buses........................................................................................ 3–6
3.5.1 End-Bus SCSI Bus Signal Converter Terminators ........................................ 3–7
3.5.2 Mid-Bus SCSI Bus Signal Converter............................................................ 3–8

Glossary
Index
Figures
Figure 1–1 DWZZx SCSI Bus Signal Converter SBB (Front) ..................................... 1–2
Figure 1–2 DWZZx SCSI Bus Signal Converter SBB (Rear) ...................................... 1–2
Figure 2–1 Typical SCSI Bus Signal Converter End-Bus Cabling............................... 2–3
Figure 2–2 End-Bus DWZZA Bus Terminators .......................................................... 2–8
Figure 2–3 H885–A Trilink Connector ....................................................................... 2–8
Figure 2–4 Mid-Bus DWZZA Bus Terminators .......................................................... 2–9
Figure 2–5 Mid-Bus DWZZA Cabling...................................................................... 2–10
Figure 3–1 Typical SCSI Bus Signal Converter End-Bus Cabling............................... 3–3
Figure 3–2 End-Bus DWZZB Bus Terminators .......................................................... 3–8
Figure 3–3 H885–A Trilink Connector ....................................................................... 3–8
Figure 3–4 Mid-Bus DWZZB Bus Terminators .......................................................... 3–9
Figure 3–5 Mid-Bus DWZZB Cabling...................................................................... 3–10

iii

Tables
Table 2–1 StorageWorks SCSI Buses ......................................................................... 2–5
Table 2–2 SCSI Cable Types...................................................................................... 2–6
Table 3-1 StorageWorks SCSI Buses.......................................................................... 3–5
Table 3-2 SCSI Cable Types....................................................................................... 3–6

Preface
The StorageWorks Solutions DWZZx SCSI Bus Signal Coverters introduces the 8- and 16-Bit
StorageWorks™ Building Blocks (SBB) SCSI bus converters which provide a small
computer system interface between controllers, host, or their SCSI adapters. This guide also
describes the components, installation, replacement procedures, and specifications.
This guide and the StorageWorks Solutions Configuration Guide, describes the complete
subsystem and comprises the basic 8- and 16-bit StorageWorks documentation set. Other
documentation for this product line is listed in the related documents section.

Intended Audience
This publication is for use by customers and Digital™ employees responsible for configuring,
installing, and maintaining the StorageWorks subsystem and its components.
_____________________________ Note ___________________________
Shelf installation procedures are cabinet specific and are not included in this
guide.
______________________________________________________________

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 also is used to indicate cross–references.

Structure
This manual is organized as follows:
Chapter 1

Introduction Provides a product overview of the StorageWorks.SCSI bus
signal converters.

Chapter 2

DWZZA Signal Bus Converters Describes the DWZZA StorageWorks
8-bit bus signal converters.

Chapter 3

DWZZB Signal Bus Converters Describes the DWZZB StorageWorks
16- bit bus signal converters.

Glossary
Index

Related Documents
Listed below are the StorageWorks-related user documents organized by use, system, or
product.
StorageWorks Related Documentation
Document Title

Order Number
StorageWorks Primary Publications

StorageWorks Solutions Configuration Guide

EK–BA350–CG

StorageWorks Solutions Shelf and SBB User's Guide

EK–BA350–UG

StorageWorks Solutions BA356–SB 16-Bit Shelf User's Guide

EK–BA356–UG

StorageWorks RAID Array 110 Subsystem
DEC RAID Utilities User's Guide

EK–DECRA–UG

HSZ10–AA Controller Site Preparation Guide

EK–HSZ10–IN

StorageWorks Expansion Storage Pedestal User's Guide

EK–SMCPA–UG

StorageWorks RAID Array 110 Subsystem User's Guide

EK–SM2CA–UG

StorageWorks RAID Array 110 Utility for MS–DOS User's Guide

AA–Q0N5A–TE

StorageWorks RAID Array 110 Utility for Novell NetWare User's Guide

AA–Q0N4A–TE

StorageWorks RAID Array 110 Utility for SCO UNIX User's Guide

AA–Q0N6A–TE

StorageWorks Array Controller 140–Series
StorageWorks Array Controller HS Family of Array Controllers User's Guide

EK–HSFAM–UG

StorageWorks BA350–MA Controller Shelf User's Guide

EK–350MA–UG

Rackmount StorageSubsystem and HSC™ Intelligent I/O Servers
HSC Controller User's Guide

AA–PFSQA–TK

HSC Controller Installation Manual

EK–HSCMN–IN

StorageWorks Enclosures

BA35X–VA Vertical Mounting Kit User's Guide

EK–350SV–UG

BA35X–KB Deskside Expansion Unit User’s Guide

EK–350KB–UG

InfoServer 1000 Installation and Owner's Guide

EK–INFLC–OM

StorageWorks Solutions Desktop Expansion Unit User's Guide

EK–BA353–UG

StorageWorks Solutions SW500 and SW800 Cabinet Metric Shelf Bracket Kit
Installation Guide

EK–35XRD–IG

StorageWorks Solutions HSR95-Series Cabinet Metric Shelf Bracket Kit

EK–35XRC–IG

Document Title
Installation Guide

Order Number

StorageWorks RETMA Shelf Rail Kit Installation Guide

EK–35XRB–IG

StorageWorks Solutions SW500-Series Cabinet Installation and User's Guide

EK–SW500–IG

StorageWorks Solutions SW500-Series Cabinet Cable Distribution Unit
Installation Guide

EK–SW5CU–IG

StorageWorks Solutions SW800-Series Data Center Cabinet Cable
Distribution Unit Installation Guide

EK–SWCDU–IS

StorageWorks Solutions SW800-Series Data Center Cabinet Installation and
User's Guide

EK–SW800–IG

Instructions for Installation of the Tape Bezel Kit on SF400 Series Cabinets*
Storage Devices
StorageWorks Solutions 3½-Inch Storage Device Installation Guide

EK–MC350–IG

StorageWorks Solutions 5¼-Inch Storage Device Installation Guide

EK–MC525–IG

TZ86–VA Cartridge Tape Drive Device Addresses

EK–TZ86A–UG

TZ87–VA Cartridge Tape Drive Device Addresses

EK–TZ87A–DA

StorageWorks Solutions TZ8x7–Series Tape Drive SCSI Bus Configuration
and Installation Guide

EK–TZ8X7–IG

General Reference Publications
Digital Systems and Options Catalog

†

Small Computer System Interface, An Overview

EK–SCSIS–OV

Small Computer System Interface, A Developer's Guide†

EK–SCSIS–DK

* Applies also to StorageWorks cabinets.
† Available from your Digital account representative.

vii

1
Introduction
The StorageWorks Solutions DWZZx 8-and 16-Bit Bus Converter User's Guide is part of the
basic StorageWorks documentation set. This guide provides information to install, configure
and operate DWZZx bus converters. The information contained in this document is
supplemented by the system and shelf documentation listed in the Related Documents section
of the Preface.

1.1 StorageWorks DWZZx Components
See the StorageWorks Solutions Configuration Guide for a complete listing of the
StorageWorks family products.
The scope of this guide is limited to providing information about the following:
•

Installation

•

Terminators

•

Shelf compatibility

•

Cable requirements

1.2 DWZZx Bus Signal Converter Description
The SCSI buses presented in this guide are of the following types:
•

A differential physical bus

•

A single-ended physical bus

•

A logical bus is a single-ended physical bus connected to a differential physical bus by a
SCSI bus signal converter.

The BA350 is an 8-bit SBB shelf and the BA356 is a 16-bit SBB shelf. Both are singleended, SCSI-2 buses. Some controllers and hosts, or their SCSI adapters, use a differential
SCSI bus. Singled-ended and differential buses are incompatible. The SCSI protocol
disables these buses when they are connected together.
The StorageWorks DWZZx SCSI bus signal converter (see Figure ) is a differential SCSI to
SCSI adapter, that permits connecting these buses together without modifying the SCSI
devices. The DWZZx-series SCSI bus signal converter establishs compatibility between the
host SCSI bus and the BA350 or BA356 SBB shelf SCSI bus, thereby extending the length of
the SCSI bus

Introduction 1–1

Figure 1–1 DWZZx SCSI Bus Signal Converter SBB (Front)

CXO-4543A-MC

Figure 1–2 DWZZx SCSI Bus Signal Converter SBB (Rear)

CXO-4544A-MC

1–2 Introduction

2
DWZZA SCSI Bus Signal Converters
This chapter discusses the DWZZA-series small computer system interface (SCSI) bus signal
converters.
_____________________________ Note ___________________________
The discussion of the DWZZA-series SCSI bus signal converters in this chapter
is limited to the models, applications, cables, and configurations applicable to the
StorageWorks building block (SBB) BA350 shelves. The capabilities and use of
these converters in other environments or with other SCSI systems are not within
the scope of this chapter.
______________________________________________________________

2.1 DWZZA Description
The BA350 shelf SCSI bus is an 8-bit, single-ended, SCSI-2 bus. Some controllers and hosts,
or their SCSI adapters, use a 16-bit, differential SCSI bus. Singled-ended and differential
buses are incompatible. The SCSI protocol disables these buses when connected together.
The DWZZA SCSI bus signal converter permits the connection of these buses without
modifying the SCSI devices. The DWZZA SCSI bus signal converter establishes
compatibility between the host SCSI bus and the BA350 shelf SCSI bus.
There are two SCSI bus signal converters used with StorageWorks BA350 shelf, the
DWZZA–AA and the DWZZA–VA. Electrically and operationally, these models are
identical. The primary differences are as follows:
•

The DWZZA–AA is a desktop model with a self-contained power supply that is
connected to either a BA350 shelf or a DWZZA–VA converter. The DWZZA–AA has
two female cable connectors, a 68-pin, high-density and a 50-pin, low-density.

•

The DWZZA–VA is installed in slot 0 of a BA350 shelf.

•

It has a single 68-pin, high-density female cable connector.
______________________________Note ___________________________
The DWZZA–VA input connector is a 68-pin, differential connector. There is no
provision for connecting a 50-pin, single-ended connector to the DWZZA–VA.
______________________________________________________________

The following is a list of the SCSI buses as presented in this chapter:
•

A differential physical bus

•

A single-ended physical bus

•

A logical bus is a single-ended physical bus connected to a differential physical bus by a
SCSI bus signal converter

DWZZA SCSI Bus Signal Converters 2–1

2.2 DWZZA Features and Functions
The following is a list of the features and functions of the DWZZA SCSI bus signal
converter:
•

The DWZZA SCSI bus signal converter converts two physical buses (a single-ended bus
and a differential bus) into a single logical bus.
_____________________________ Note ___________________________
The 16-bit differential host or controller bus is operated in the 8-bit mode.
______________________________________________________________

•

The length of the logical bus is equal to the length of the two physical buses.

•

The logical bus has a total of eight device addresses (0 through 7).

•

The converter does not use a SCSI device address.

•

The DWZZA SCSI bus signal converter establishes a physical connection between a 16bit, differential bus operating in the 8-bit mode and an 8-bit, single-ended SCSI device
(communication between the host and the BA350 is in 8-bit mode).

•

Supports data transfers at rates of up to 10 million transfers per seconds (10 MB/s 1 ).

•

The converter operation is transparent to both buses.

2.3 Installing DWZZA SCSI Bus Signal Converters
The manner in which SCSI bus signal converters are installed is primarily based upon the
SCSI host.
_____________________________ Note____________________________
Unless otherwise stated, the DWZZA signal converters are installed in the endbus position. This requires that both the differential bus and the single-ended bus
be terminated within the DWZZA SCSI bus signal converter.
______________________________________________________________
See below and Figure , for three host to BA350 shelf connections:
1.

A DWZZA SCSI bus signal converter is not required when using a single-ended host.
Connect the host SCSI controller or adapter directly to the BA350 shelf with a single
ended cable.

Connect a differential host operating in the 8-bit mode, directly to the DWZZA–VA
SCSI bus signal converter.

To create a logical bus longer than the single-ended physical bus, install two DWZZA
SCSI bus signal converters: DWZZA–AA, and DWZZA–VA.
•

The desktop model, DWZZA–AA, connects to the host with a 50-conductor, singleended (SCSI-A) cable (BN23G or BN21H).

•

The desktop model connects to the DWZZA–VA with a 68-conductor, differential
(SCSI-P) cable, such as a BN21K or BN21L.

1 This rate is supported only when at least one drive supports the 10 MB/s transfer

rate and the bus has been designed as a fast bus.
2–2 DWZZA SCSI Bus Signal Converters

Figure 2–1 Typical SCSI Bus Signal Converter End-Bus Cabling

SINGLEENDED
SCSI
CONTROLLER

SBB
SHELF

SINGLEENDED
CABLE

JA-1

DIFFERENTIAL
SCSI
CONTROLLER

SBB
SHELF
DWZZA-VA
DIFFERENTIAL
CABLE
SLOT 0

SINGLEENDED
SCSI
CONTROLLER

SBB
SHELF
DWZZA-VA

DWZZA-AA
SINGLEENDED
CABLE

DIFFERENTIAL
CABLE
SLOT 0
CXO-3837A-MC

The DWZZA SCSI bus signal converter extends the maximum length of the SCSI bus. This
length is measured from the terminator on the SCSI host, to the terminator on the BA350
shelf, and includes the following:
•

The length of all cables

•

The distance from the host terminator to the host SCSI cable connector

•

The distance from the BA350 shelf input connector or the DWZZA–VA connector to the
shelf terminator

DWZZA SCSI Bus Signal Converters 2–3

Table 2–1 lists the maximum bus lengths using the end-bus configuration for all DWZZAs.
_____________________________ Note ___________________________
The maximum SCSI bus length is not the same as maximum cable length.
The longest StorageWorks BN21K or BN21L SCSI-P cable is 23 meters. Do not
use a longer SCSI-P cable.
______________________________________________________________
Table 2–1 StorageWorks SCSI Buses
SCSI Bus

DWZZAs

SCSI Bus Length
Cable-Host†

Cable

Type

MB/s

-VA

-AA

Shelf*

Maximum‡

Type

Order No.

Fast

0.9 m (3.0 ft)

2.1 m (6.9 ft)

3 m (9.8 ft)

SE§

BN21H

Slow

0.9 m (3.0 ft)

5.1 m (16.7 ft)

6 m (19.7 ft)

BN21H

No SCSI Bus Signal_Converters

Differential SCSI Host
One SCSI Bus Signal Converter
Fast

3 m (9.8 ft)

23 (75.5 ft)

26 m (85.3 ft)

DF#

BN21K, BN21L

Slow

6 m (19.7 ft)

23 (75.5 ft)

29 m (95.1 ft)

BN21K, BN21L

Single-Ended SCSI Host
Two SCSI Bus Signal Converters
Fast

3 m (9.8 ft)

26 m (85.3 ft)

29 m (95.1 ft)

SE
DF

BN23G, BN21H
BN21K, BN21L

Slow

6 m (19.7 ft)

29 m (95.1 ft)

35 m (114.8 ft)

SE
DF

BN23G, BN21H
BN21K, BN21L

* First shelf input connector to last shelf terminator.
† Host terminator to shelf input connector or shelf DWZZA–A input connector.
‡ Host terminator to shelf terminator.
§ SE–SCSI–A SCSI cable, 50-pin connector.
# DF–SCSI–A SCSI cable, 68-pin connector.

The end-bus configuration terminates all cables in the converter, the BA350 shelf and in the
host.
_____________________________ Note____________________________
This configuration effectively starts a new bus at each connection
______________________________________________________________
For example, when using a single-ended bus and no converters, the maximum length of the
single-ended SCSI bus from the host terminator to the BA350 shelf terminator is 6 meters
(19.7 ft). By using two converters, the maximum distance from the host terminator to the
BA350 shelf terminator is theoretically 37 meters (121.4 feet). The actual maximum length
with approved cables is as shown in Table 2–1.
•

The maximum bus length from the host terminator to the desktop converter 50-pin
connector is either 3 meters (9.8 ft) or 6 meters (19.7 ft) depending upon the bus speed.

•

The maximum cable length from desktop converter 68-pin connector to the BA350 shelf
converter 68-pin connector is 23 meters (75.5 ft).

2–4 DWZZA SCSI Bus Signal Converters

•

The maximum bus length from the BA350 shelf converter backplane connector, to the
shelf terminator is either 3 meters (9.8 ft) or 6 meters (19.7 ft) depending upon the bus
speed.

2.4 SCSI Cables
The StorageWorks Solutions Configuration Guide describes SCSI cables in detail. The
particular cable used with a SCSI bus signal converter depends upon the following:
1.

The bus type:
•

A DWZZA–AA has a 68-pin, high-density, differential connector and a 50-pin, lowdensity, single-ended connector.

•

A DWZZA–VA has one 68-pin, high-density, cable connector, a, differential
connector for connecting to a host or controller. The DWZZA–VA single-ended
SCSI bus is routed to the BA350 shelf through the 96-pin connector on the rear of
the DWZZA–VA SCSI bus signal converter.

The maximum allowable bus length.

The cable connector clearance. In some cases you must use a right-angle connector
because there is not enough clearance to use a straight connector.

DWZZA compatible cable types are listed in Table 2–2.
Table 2–2 SCSI Cable Types
Bus Connector

Cable Type

Connectors

DWZZA-VA SBB SCSI Bus Signal Converter Compatible Cables
Single-ended

N/A

The single-ended connector is a 96-pin, high-density,
connector that mates with the SBB shelf connector.

Differential

BN21K-23

One 68-pin, high-density, straight, connector and one 68pin, high-density, right-angle connector

Differential

BN21L-23

Two 68-pin, high-density, right-angle connectors

DWZZA-AA Desktop SCSI Bus Signal Converter Compatible Cables
Single-ended
(low-density host)

BC06P

Two 50-pin, low-density, straight connectors with bale
locks.

Single-ended
(low-density host)

BN23G

50-pin, high-density, straight connector and 50-pin, lowdensity, straight connector.

Differential

BN21K-23

One 68-pin, high-density, straight connector and one 68pin, high- density, right-angle connector.

Differential

BN21L-23

Two 68-pin, high-density, right-angle connectors

2.5 Terminating SCSI Buses
All SCSI buses are terminated at the physical ends of the bus or cable. This is true even
when using a DWZZA SCSI bus signal converter. Both DWZZA SCSI bus signal 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 signal
converter for either end-bus (refer to Section 2.5.1) or mid-bus (refer to Section 2.5.2)
operation.

DWZZA SCSI Bus Signal Converters 2–5

___________________________ CAUTION _________________________
To prevent SCSI bus malfunction, do not remove the DWZZA SCSI bus signal
converter or disconnect the SCSI cable when power is on.
______________________________________________________________

2.5.1 End-Bus SCSI Bus Signal Converter Terminators
Use the following procedure to install the single-ended and differential terminators when the
DWZZA-series SCSI bus signal converter is installed in the end-bus position:
___________________________ CAUTION _________________________
To prevent damage, remove the SBB bezel only as required and use minimal
pressure when pushing down on the mounting tabs.
______________________________________________________________
___________________________ CAUTION _________________________
Do not attempt the following procedure without proper precautions against
electrostatic discharge (ESD). When you remove the cover from any enclosure or
device, wear an ESD grounding wrist strap.
______________________________________________________________
1.

Turn off the power and remove the input power cable.

Disconnect the SCSI cables.

Remove either the SBB bezel and cover, or the desktop cover.

Install jumper J2 (see Figure ), the single-ended SCSI-2 bus termination, to terminate the
single-ended bus.

Install the five resistor single-inline-packages (SIPs) to terminate the SCSI-P cable.

Replace the SBB cover and bezel, or replace the desktop cover.

Label the SBB bezel or the desktop cover 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 cable.

2–6 DWZZA SCSI Bus Signal Converters

Figure 2–2 End-Bus DWZZA Bus Terminators
SINGLE-ENDED
SCSI-2 TERMINATION

DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

68-PIN
CONNECTOR

CXO-3836A-MC

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

2.5.2 Mid-Bus SCSI Bus Signal Converter Terminators
Use an H885–AA trilink connector (see Figure ), to place the BA350 shelf DWZZA SCSI bus
signal converter in the mid-bus position. Use the following procedure to configure the
differential connector for mid-bus operation:

Figure 2–3 H885–A Trilink Connector

REAR VIEW

FRONT VIEW
CXO-3851A-MC

DWZZA SCSI Bus Signal Converters 2–7

_____________________________ Note ___________________________
Normally, this procedure is completed only during initial installation of the SCSI
bus signal converter.
______________________________________________________________
___________________________ CAUTION _________________________
Do not attempt the following procedure without proper precautions against
electrostatic discharge (ESD). When you remove the cover from any enclosure or
device, wear an ESD grounding wrist strap.
______________________________________________________
1.

Turn off the power and remove the input power cable.

Disconnect the SCSI cables.

Remove either the SBB bezel and cover, or the desktop cover.

Install jumper J2 (see Figure ), the single-ended SCSI-2 bus terminator, to terminate the
single-ended bus.

Remove the five differential bus resistor SIPs.

Figure 2–4 Mid-Bus DWZZA Bus Terminators
SINGLE-ENDED
SCSI-2 TERMINATION

DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

68-PIN
CONNECTOR

CXO-3872A-MC

Replace the SBB cover and bezel, or the desktop cover.

Install the H885–AA trilink connector in the differential connector (see Figure ).

Connect the input SCSI-P cable from the host or the desktop converter to the trilink
connector.

2–8 DWZZA SCSI Bus Signal Converters

Figure 2–5 Mid-Bus DWZZA Cabling

DIFFERENTIAL
SCSI HOST

H885A
TRILINK
CONNECTOR

SBB
SHELF
DWZZA-VA

MID-BUS
POSITION

SBB
SHELF
DWZZA-VA

END-BUS
POSITION
CXO-3871A-MC

Connect a SCSI-P cable from the trilink connector to the input connector on the second
DWZZA–VA.

10. Make sure that the differential bus is terminated on the last DWZZA on the bus (refer to
Section 2.5.1).
11. Label the SBB bezels with the status of both the differential terminator and the singleended terminator, as either IN or OUT.
12. Install the SBB DWZZA signal converter.
13. Connect the SCSI cable.
14. Connect the input power cable and apply power to the shelf.
15. Observe the system to determine if the SCSI bus and devices are functioning properly.

DWZZA SCSI Bus Signal Converters 2–9

3
DWZZB SCSI Bus Signal Converters
This chapter discusses the DWZZB-series small computer system interface (SCSI) bus signal
converters.
_____________________________ Note ___________________________
The discussion of the DWZZB-series SCSI bus signal converters in this chapter
is limited to the models, applications, cables, and configurations applicable to the
StorageWorks building block (SBB) BA356 shelf. The capabilities and use of
these converters in other environments or with other SCSI systems are not within
the scope of this chapter.
______________________________________________________________

3.1 DWZZB Description
The BA356 shelf SCSI bus is a 16-bit, single-ended, SCSI-2 bus. Some controllers and
hosts, or their SCSI adapters, use a 16-bit, differential SCSI bus. Singled-ended and
differential buses are incompatible. The SCSI protocol disables these buses when connected
together.
The DWZZB SCSI bus signal converter permits the connection of these buses without
modifying the SCSI devices. The DWZZB SCSI bus signal converter establishes
compatibility between the host SCSI bus and the BA356 shelf bus.
There are two DWZZB SCSI bus signal converters used with StorageWorks BA356 shelf, the
DWZZB–AA and the DWZZB–VW. Electrically and operationally, these models are
identical. The primary differences are as follow:
•

The DWZZB–AA is a desktop model with a self-contained power supply that is
connected to either an BA356 shelf or a DWZZB–VW converter. The DWZZB–AA has
two female, 68-pin, high-density, cable connectors.

•

The DWZZB–VW is installed in slot 0 of a BA356 shelf.

•

It has a single 68-pin, high-density female cable connector.
______________________________Note ___________________________
The DWZZB–VW input connector is a 68-pin, differential connector. There is no
provision for connecting a 50-pin, single-ended connector to the DWZZB–VW.
______________________________________________________________

The following is list of the SCSI buses presented in this chapter:
•

A differential physical busA single-ended physical bus

•

A single-ended physical bus connected to a differential physical bus by a DWZZB SCSI
bus signal converter forms a logical bus

DWZZB SCSI Bus Signal Converters 3–1

3.2 DWZZB Features and Functions
The following is a list of the features and functions of the DWZZB SCSI bus signal
converter:
•

The DWZZB SCSI bus signal converter changes two physical buses (a single-ended bus
and a differential bus) into a single logical bus.
_____________________________ Note ___________________________
The 16-bit differential host or controller bus is operated in either a 8-bit mode, or
a 16-bit mode.
______________________________________________________________

•

The length of the logical bus is equal to the length of the two physical buses.

•

The logical bus has a total of sixteen device addresses (0 through 15).

•

The converter does not use a SCSI device address.

•

The DWZZB SCSI bus signal converter establishes a physical connection between a 16bit, differential bus operating in either an 8-bit mode, or a 16-bit mode, and an 16-bit,
single-ended SCSI device (communication between the host and the BA356 is in 16-bit
mode).

•

Data transfers at rates of up to 20 Bytes or 10 million transfers per seconds (20 MB/s2 )
are supported.

•

The converter operation is transparent to both buses.

3.3 Installing DWZZB SCSI Bus Signal Converters
The manner in which SCSI bus signal converters are installed is primarily based upon the
SCSI host.
_____________________________ Note____________________________
Unless otherwise stated, the DWZZB signal converters are installed in the endbus position. This requires that both the differential bus and the single-ended bus
be terminated within the DWZZB SCSI bus signal converter.
______________________________________________________________
See below and Figure , for three host to BA356 shelf connections:
1.

A DWZZB SCSI bus signal converter is not required, when using a single-ended host.
Connect the host SCSI controller or adapter directly to the BA356 shelf with a singleended cable.

Connect a differential host operating in either the 8-bit mode, or 16-bit mode directly to
the DWZZB SCSI bus signal converter.

To create a logical bus longer than the single-ended physical bus, install two DWZZB
SCSI bus signal converters: DWZZB–AA, and DWZZB–VW.
•

The desktop model, DWZZB-AA, connects to the host with a 68-conductor, singleended (SCSI-P) cable. The cable type is dependent on the host system used.

2 This rate is supported only when at least one drive supports the 20 MB/s

rate and the bus has been designed as a fast bus.
3–2 DWZZB SCSI Bus Signal Converters

transfer

•

The desktop model connects to the DWZZB-VW with a 68-conductor, differential
(SCSI-P) cable, such as a BN21K or BN21L.

Figure 3–1 Typical SCSI Bus Signal Converter End-Bus Cabling

SINGLEENDED
SCSI
CONTROLLER

SBB
SHELF

SINGLEENDED
CABLE

JA-1

DIFFERENTIAL
SCSI
CONTROLLER

SBB
SHELF

DIFFERENTIAL
CABLE

SLOT 0

DWZZB-VW
PERSONALITY
MODULE

SINGLEENDED
SCSI
CONTROLLER

SBB
SHELF
DWZZB-VA
SINGLEENDED
CABLE

DIFFERENTIAL
CABLE

SLOT 0

DWZZB-VW
PERSONALITY
MODULE
CXO-4540A-MC

The DWZZB SCSI bus signal converter extends the maximum length of the SCSI bus. This
length is measured from the terminator on the SCSI host, to the terminator on the BA356
shelf, and includes the following:
•

The length of all cables

•

The distance from the host terminator to the host SCSI cable connector

•

The distance from the BA356 shelf input connector or the DWZZB-VW connector to the
shelf terminator

DWZZB SCSI Bus Signal Converters 3–3

Table 3-1 lists the maximum bus lengths using the end-bus configuration for all DWZZBs.
_____________________________ Note ___________________________
Maximum SCSI bus length is not the same as maximum cable length. The
longest StorageWorks BN21K or BN21L SCSI-P cable is 23 meters. Do not use a
longer SCSI-P cable.
______________________________________________________________
Table 3-1 StorageWorks SCSI Buses
SCSI Bus

DWZZBs

Type

MB/s

-VW

-AA

SCSI Bus Length
Shelf*

Fast

0.9 m (3.0 ft)

2.1 m (6.9 ft)

Slow

0.9 m (3.0 ft)

5.1 m (16.7 ft)

Cable-Host†

Cable
Maximum‡

Type

Order No.

3 m (9.8 ft)

SE§

BN21K, BN21L

6 m (19.7 ft)

BN21K, BN21L

No SCSI Bus Signal_Converters

Differential SCSI Host
One SCSI Bus Signal Converter
Fast

3 m (9.8 ft)

23m(75.5 ft)

26 m (85.3 ft)

DF#

BN21K, BN21L

Slow

6 m (19.7 ft)

23m(75.5 ft)

29 m (95.1 ft)

BN21K, BN21L

Single-Ended SCSI Host
Two SCSI Bus Signal Converters
Fast

3 m (9.8 ft)

26 m (85.3 ft)

29 m (95.1 ft)

SE
DF

BN21M
BN21K, BN21L

Slow

6 m (19.7 ft)

29 m (95.1 ft)

35 m (114.8 ft)

SE
DF

BN21M
BN21K, BN21L

* First shelf input connector to last shelf terminator.
† Host terminator to shelf input connector or shelf DWZZB–A input connector.
‡ Host terminator to shelf terminator.
§ SE–SCSI–A SCSI cable, 68-pin connector.
# DF–SCSI–A SCSI cxable, 68-pin connector.

The end-bus configuration terminates all cables in the converter, the BA356 shelf and in the
host.
_____________________________ Note____________________________
This configuration effectively starts a new bus at each connection
______________________________________________________________
For example, when using a single-ended bus and no DWZZB converters, the maximum
length of the single-ended SCSI bus from the host terminator to the BA356 shelf terminator is
6 meters (19.7 ft). By using two DWZZB converters, the maximum distance from the host
terminator to the BA356 shelf terminator would theoretically be 37 meters (121.4 feet).
However, the actual maximum length when using approved cables is as shown in Table 3-1.
•

The maximum bus length from the host terminator to the desktop DWZZB converter 68pin connector is either 3 meters (9.8 ft) or 6 meters (19.7 ft) depending upon the bus
speed.

•

The maximum cable length from desktop converter 68-pin connector to the BA356 shelf
converter 68-pin connector is 23 meters (75.5 ft).

3–4 DWZZB SCSI Bus Signal Converters

•

The maximum bus length from the BA356 shelf converter backplane connector to the
shelf terminator can be either 3 meters (9.8 ft) or 6 meters (19.7 ft) depending upon the
bus speed.

3.4 SCSI Cables
The StorageWorks Solutions Configuration Guide describes SCSI cables in detail. The
particular cable used with a DWZZB SCSI bus signal converter depends upon the following:
1.

The bus type:
•

A DWZZB–AA has two (2) 68-pin, high-density connectors, one at the single ended
end and the other at the differential end.

•

A DWZZB–VW has one 68-pin, high-density, differential cable connector, for
connecting to a host or controller. The DWZZB–VW single-ended SCSI bus is
routed to the BA356 shelf through the 96-pin connector on the rear of the
DWZZB–VW SCSI bus signal converter.

The maximum allowable bus length.

The cable connector clearance. In some cases you must use a right-angle connector
because there is not enough clearance to use a straight connector.

DWZZB compatible cable types are listed in Table 3-2.
Table 3-2 SCSI Cable Types
Bus Connector

Cable Type

Connectors

DWZZB-VW BA356 SCSI Bus Signal Converter Compatible Cables
Single-ended

N/A

The single-ended connector is a 96-pin, high-density
connector that mates with the BA356 shelf connector.

Differential

BN21K-23

One 68-pin, high-density, straight, connector and one 68pin, high-density, right-angle connector

Differential

BN21L-23

Two 68-pin, high-density, right-angle connectors

DWZZB-AA Desktop SCSI Bus Signal Converter Compatible Cables
Differential

BN21K-23

One 68-pin, high-density, straight connector and one 68pin, high- density, right-angle connector.

Differential

BN21L-23

Two 68-pin, high-density, right-angle connectors

3.5 Terminating SCSI Buses
All SCSI buses are terminated at the physical ends of the bus or cable. This is true even
when using a DWZZB SCSI bus signal converter. Both DWZZB SCSI bus signal 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 DWZZB SCSI bus signal
converterfor either end-bus (refer to Section 3.5.1) or mid-bus (refer to Section 3.5.2)
operation.

DWZZB SCSI Bus Signal Converters 3–5

___________________________ CAUTION _________________________
To prevent SCSI bus malfunction, do not remove the DWZZB SCSI bus signal
converter or disconnect the SCSI cable when power is on.
______________________________________________________________

3.5.1 End-Bus SCSI Bus Signal Converter Terminators
Use the following procedure to install the single-ended and differential terminators when the
DWZZB-series SCSI bus signal converter is installed in the end-bus position:
___________________________ CAUTION _________________________
To prevent damage, remove the SBB bezel only as required and use minimal
pressure used when pushing down on the mounting tabs.
______________________________________________________________
___________________________ CAUTION _________________________
Do not attempt the following procedure without proper precautions against
electrostatic discharge (ESD). When you remove the cover from any enclosure or
device, wear an ESD grounding wrist strap.
______________________________________________________________
1.

Turn off the power and remove the input power cable.

Disconnect the SCSI cables.

Remove either the SBB bezel and cover, or the desktop cover.

Install jumpers W1 and W2 (see Figure ), the single-ended SCSI-2 bus termination, to
terminate the single-ended bus.

Install the five resistor single-inline-packages (SIPs) to terminate the differential.

Replace the SBB cover and bezel, or replace the desktop cover.

Label the SBB bezel or the desktop cover 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 cable.

3–6 DWZZB SCSI Bus Signal Converters

Figure 3–2 End-Bus DWZZB Bus Terminators
SINGLE-ENDED
SCSI-2 TERMINATION

DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

W1
68-PIN
CONNECTOR

CXO-4541A-MC

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

3.5.2 Mid-Bus SCSI Bus Signal Converter
Use an H885-AA trilink connector (see Figure ), to place the BA356 shelf DWZZB SCSI bus
signal converter in the mid-bus position. Use the following procedure to configure the
differential connector for mid-bus operation:

Figure 3–3 H885–A Trilink Connector

REAR VIEW

FRONT VIEW
CXO-3851A-MC

DWZZB SCSI Bus Signal Converters 3–7

_____________________________ Note ___________________________
Normally, this procedure is only completed during initial installation of the SCSI
bus signal converter.
______________________________________________________________
___________________________ CAUTION _________________________
Do not attempt the following procedure without proper precautions against
electrostatic discharge (ESD). When you remove the cover from any enclosure or
device, wear an ESD grounding wrist strap.
______________________________________________________

Turn off the power and remove the input power cable.

Disconnect the SCSI cables.

Remove either the SBB bezel and cover, or the desktop cover.

Install jumpers W1 and W2 (see Figure ), the single-ended SCSI-2 bus terminator, to
terminate the single-ended bus.

Remove the five differential bus resistor SIPs.

Figure 3–4 Mid-Bus DWZZB Bus Terminators
SINGLE-ENDED
SCSI-2 TERMINATION

DIFFERENTIAL
TERMINATOR
RESISTOR SIPS

W1
W2

68-PIN
CONNECTOR

CXO-4542A-MC

Replace the SBB cover and bezel, or the desktop cover.

Install the H885–AA trilink connector in the differential connector (see Figure ).

Connect the input SCSI-P cable from the host or the desktop converter to the trilink
connector.

3–8 DWZZB SCSI Bus Signal Converters

Figure 3–5 Mid-Bus DWZZB Cabling

DIFFERENTIAL
SCSI HOST

H885A
TRILINK
CONNECTOR

SBB
SHELF 1

MID-BUS
POSITION

DWZZB-VW
PERSONALITY
MODULE

SBB
SHELF
END-BUS
POSITION

DWZZB-VW
PERSONALITY
MODULE

CXO-4539A-MC

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

10. Make sure that the differential bus is terminated on the last DWZZB on the bus (refer to
Section 3.5.1).
11. Label the SBB bezels with the status of both the differential terminator and the singleended terminator,as either IN or OUT.
12. Install the SBB DWZZB signal converter.
13. Connect the SCSI cable.
14. Connect the input power cable and apply power to the shelf.
15. Observe the system to determine if the SCSI bus and devices are functioning properly.

DWZZB SCSI Bus Signal Converters 3–9

Glossary
adapter
See SCSI bus signal converter.
Battery backup unit
See BBU.
BBU
Battery backup unit. StorageWorks power unit option that extends power availability after the
loss of primary ac power, or a power supply to protect against the corruption or loss of data.
_____________________________ Note ___________________________
The BBU does not provide power for the operation of a storage device. It
provides power only for protecting data.
______________________________________________________________
building block shelf
See SBB.
cold swap
A method of device replacement that requires that power be removed from one or more
shelves in a cabinet. User applications that are not dependent upon the devices being
swapped are impacted as a result. This method is used when conditions preclude the use of a
warm swap or hot swap method. Normally, this method is used only when installing or
upgrading a StorageWorks subsystem.
See also warm swap and hot swap.
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.
controller and SBB shelf
A generic reference to a StorageWorks shelf that can contain both controller SBBs and
storage SBBs (for example, a BA350–EA shelf).
controller shelf
Any StorageWorks shelf that contains only controllers and cache memories (for example, a
BA350–MA shelf).
daisy chain
Two or more StorageWorks shelves that are connected.
deskside expansion unit
The StorageWorks floor mounted stand that encloses a BA356–SB SBB shelf.
Glossary–1

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.
disk
A storage device supporting random access to fixed size blocks of data.
DWZZA
A StorageWorks compatible 8-bit SCSI bus signal converter.
See SCSI bus signal converter.
DWZZB
A StorageWorks compatible 16-bit SCSI bus signal converter.
See SCSI bus signal converter.
electrostatic discharge
See ESD.
ESD
Electrostatic discharge is the discharge of a potentially harmful static electric voltage as a
result of improper grounding.
full-height
(1) In the storage industry, a device of conventional dimensions. (2) A single device mounted
in an 5¼-inch SBB.
half-height
(1) In the storage industry, a device of conventional dimensions, except for height. (2) A
device that occupies only one-half of a 5¼-inch SBB. The first half-height device is always
mounted in the lower (bottom) part of the SBB. The second device in an SBB is mounted in
the upper (top) part of the SBB.
host
The primary or controlling computer or any such unit (in a multiple computer network) to
which storage is attached.
hot swap
A method of device replacement whereby the complete system remains on line and active
during device removal or insertion. The device being removed or inserted is the only device
that cannot perform operations during this process. User applications that are not dependent
upon the device being swapped are not impacted.
See also cold swap and warm swap.
logical bus
A single-ended, physical bus connected to a differential, physical bus by a SCSI bus signal
converter.

2–Glossary

personality module
The BA356 module that interfaces the single-ended SCSI-bus to the BA356 shelf.
physical bus
Two SCSI terminators separated by cables, connectors, and/or the backplane circuitry.
RAID
Redundant Array of Independent Disks. A set of storage techniques that increases the
performance and availability of a storage subsystem.
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.
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 signal 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.
SCSI mid-bus
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–A cable
A 68-conductor (34 twisted pair) cable used for single-ended, SCSI–3 bus connections.
SCSI–P cable
A 68-conductor (34 twisted pairs) cable used for differential bus connections.

Glossary–3

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.
tape controller
See controller.
target
A SCSI device that performs an operation requested by an initiator.
target ID
See SCSI device ID.
termpower
Is an electrical current that is limited by self-resetting fuses.
third-height
(1) In the storage industry, a device of conventional dimensions, except for height. (2) A
device that occupies only one-third of a 5¼-inch SBB. The first third-height device is always
mounted in the lower (bottom) part of the SBB. The second device in an SBB is mounted in
the middle (center) part of the SBB. The third device in an SBB is mounted in the upper
(top) part of the SBB.
warm swap
A method of device replacement whereby the complete system remains on line during device
removal or insertion. Activity can be suspended or paused for a brief period of time during
device insertion or removal. No booting or loading of code is permitted except on the device
being inserted. User applications that are not dependent upon the devices on the affected
SCSI bus are not noticeably impacted.
See also cold swap and hot swap.

4–Glossary

Index
—D—
DWZZA signal converters
description, 2-1
DWZZA-AA, 2-1
DWZZA-VA, 2-1
features and functions, 2-2
installation, 2-2
SCSI cables, 2-5
DWZZA terminators
end-bus, 2-6
mid bus
trilink connector, 2-7
DWZZB signal converters
description, 3-1
DWZZB-AA, 3-1
DWZZB-VW, 3-1
features and functions, 3-2
installation, 3-2
SCSI cables, 3-5
DWZZB terminators
end-bus, 3-6
mid bus
trilink connector, 3-7
DWZZx signal converters
components, 1-1
description, 1-1

end bus, 2-6
mid bus, 2-7
DWZZB
end bus, 3-6
mid bus, 3-7

—F—
features and functions
DWZZA, 2-2
DWZZB, 3-2

—I—
installation
DWZZA, 2-2
DWZZB, 3-2

—S—
SCSI cables
DWZZA, 2-5
DWZZB, 3-5
shelves
BA350, 2-1
BA350 or BA356, 1-1
BA356, 3-1

—T—
terminator power
DWZZA, 2-5
DWZZB, 3-5
terminators
DWZZA

Index–1