S T 3 2 5 5 0 N B A R R A C U D A 2 L SEAGATE
Native| Translation
------+-----+-----+-----
Form 3.5"/SLIMLINE Cylinders 3711| | |
Capacity form/unform 2147/ 2541 MB Heads 11| | |
Seek time / track 8.5/ 0.8 ms Sector/track | | |
Controller SCSI2 SI/FAST Precompensation
Cache/Buffer 512 KB SEGMENTED Landing Zone
Data transfer rate 5.500 MB/S int Bytes/Sector 512
10.000 MB/S ext SYNC
Recording method RLL 1/7 operating | non-operating
-------------+--------------
Supply voltage 5/12 V Temperature *C 5 50 | -40 70
Power: sleep W Humidity % |
standby W Altitude km |
idle 8.8 W Shock g |
seek W Rotation RPM 7200
read/write W Acoustic dBA
spin-up W ECC Bit
MTBF h 800000
Warranty Month 60
Lift/Lock/Park YES Certificates
**********************************************************************
L A Y O U T
**********************************************************************
SEAGATE ST31250/32550N/ND/W/WC/DC/WD INSTALL. GUIDE 83328920 REV E
+---------------------------------------------------------+
|1-+ |XX
|| |J4 |XXI
|| | |XXN
|+-+ |XXT
| |XXE
| N/ND Models |XXR
| |XXF
| |XXA
| |XXC
| |XXE
| |XX
| 4 Pins on ND |XX
| Models |XX
| +--6J1 |
| J2 1--+ |XXPOWER
| +-------1 |XX
+------------------------------+-------+------------------+
+---------------------------------------------------------+
|1-+ |+--+I
|| |J4 ||XX|N
|| | ||XX|T
|+-+ ||XX|E
| ||XX|R
| W/WD Models ||XX|F
| ||XX|A
| ||XX|C
| ||XX|E
| |+--+1
| |+-+J5
| 4 Pins on || |
| WD Models || |
| +--+J1 |+-1
| J2 1--+ |XXPOWER
| +-------1 |XX
+------------------------------+-------+------------------+ 1
**********************************************************************
J U M P E R S
**********************************************************************
SEAGATE ST31250/32550N/ND/W/WD/WC/DC INSTALL.GUIDE 83328920 REV.E 95
Jumper Setting
==============
J4 Setting the SCSI ID jumpers N/ND Models
------------------------------------------
Use the J4 connector to set the SCSI ID. To change the SCSI ID,
install jumpers on the appropriate pins as shown.
---+---------------------+-
| 2 o o * * * o o o o | (Front View)
| 1 o o * * * o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o * * * o o o o | SCSI ID 0 (DEFAULT)
| 1 o o * * * o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o X * * o o o o | SCSI ID 1
| 1 o o X * * o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o * X * o o o o | SCSI ID 2
| 1 o o * X * o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o X X * o o o o | SCSI ID 3
| 1 o o X X * o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o * * X o o o o | SCSI ID 4
| 1 o o * * X o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o X * X o o o o | SCSI ID 5
| 1 o o X * X o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o * X X o o o o | SCSI ID 6
| 1 o o * X X o o o o |J4
+---------------------+
---+---------------------+-
| 2 o o X X X o o o o | SCSI ID 7
| 1 o o X X X o o o o |J4
+---------------------+
SCSI ID jumpers
---------------
Each device on the SCSI chain must have a unique SCSI ID. The
host system's SCSI controller usually uses the highest-numbered
ID available; therefore the lower-numbered SCSI IDs are normally
used for the other SCSI devices such as this Barracuda disc drive.
NOTE
Most SCSI controllers (host adapters) allow you to skip a SCSI ID.
For example, you can have ID0, ID1, and ID3 (skipping ID2). Other
controllers do not allow this so be sure to refer to your system or
controller user's manual for details about its requirements for
proper SCSI device installation.
Most Barracuda disc drives are factory set with the SCSI ID set
at 0. If, after completing the installation process, the drive's
LED does not show on/off activity when the host is trying to
communicate with the drive, a duplicate SCSI ID may be the
problem. If this is the case, change the ID so that each device
on the SCSI chain has its own unique ID.
Also check your system or controller user's manual to ensure that
you have not violated its SCSI ID numbering recommendations.
WC/DC drives
------------
Setting the SCSI ID jumpers
The SCSI ID for WC drives is normally set over the SCSI bus by the
host system using connector contacts 39 (ID0), 40 (ID2), 79 (ID1),
and 80 (ID3). Systems designers may, optionally, install a remote
operator panel connection to set the SCSI ID.
J1 Terminating the drive N/ND
-----------------------------
+-------+
| X * 1 | J1 Enable SCSI terminator (DEFAULT)
| X * * |
+-------+
+-------+
| * * 1 | J1 Disable SCSI terminator
| 6 * * |
+-------+
If you are installing a Barracuda 2LP drive in a system that has
other SCSI devices installed, terminate only the end devices on
the SCSI chain. A SCSI "device" is any disc drive, scanner, tape-
backup unit, or other piece of hardware connected to your system
using the SCSI bus.
N/ND drives
-----------
ST31250N and ST32550N drives are terminated with permanently mounted
IC active terminators. If you install one of these drives and it is
not on the end of the SCSI bus, disable the terminators by removing
the jumper from pins 5 and 6 of connector J1. If you install the
drive on the end of the SCSI bus, enable termination by installing
a jumper on pins 5 and 6 of connector J1.
NOTE
Use active terminators when terminating the bus.
ST31250ND and ST32550ND drives do not have internal terminators or
any other way of adding internal termination to the drive. You
must provide external active termination (ANSI SCSI-2 Alternative
2) to these drives when termination is required.
Terminating the drive (W Models)
--------------------------------
ST31250W and ST32550W drives are terminated with permanently mounted
IC active terminators. If you install one of these drives and it is
not on the end of the SCSI bus, disable the terminators by removing
the jumper from pins 5 and 6 of connector J1. If you install the
drive on the end of the SCSI bus, enable termination by installing a
jumper on pins 5 and 6 of connector J1.
NOTE
Use active terminators when terminating the bus.
ST31250WD and ST32550WD drives do not have internal terminators or
any other way of adding internal termination to the drive. You must
provide external active termination (ANSI SCSI-2 Alternative 2) to
these drives when termination is required.
Terminating the drive WC Models
-------------------------------
ST31250WC and ST32550WC drives do not have internal terminators or
any other way of adding internal termination to the drive. You must
provide single-ended external active termination (ANSI SCSI-2
Alternative 2) to these drives when termination is required.
Terminator power
----------------
You usually will not need to change this option and can normally
leave the drive configured as it was shipped from the factory.
For information about how to change the terminator power option on
your drive.
Terminator power W Models
-------------------------
There are four possible terminator power configurations for ST31250W
and ST32550W drives. You will not normally need to change this option
and can leave the drive configured as it was shipped from the
factory.
ST31250WD and ST32550WD drives should be configured with a jumper
connecting J1 pins 1 and 3 (and no jumper on J1 pins 2 and 4).
J1 Teminator Power N MODELS
---------------------------
+-------+
| * * X | J1 Terminator power from drive (DEFAULT)
| 6 * X |
+-------+
+-------+
| * xxx | J1 Terminator power to SCSI bus
| 6 * * |
+-------+
+-------+
| * * 1 | J1 Terminator power from SCSI bus
| 6 xxx |
+-------+
+-------+
| * xxx | J1 Terminator power to SCSI bus and drive
| 6 xxx |
+-------+
J1 Terminator Power ND MODELS
-----------------------------
+-----+
| xxx | J1 Terminator power to SCSI bus
| * *2|
+-----+
There are four possible terminator power configurations for ST31250N
and ST32550N drives. You will not normally need to change this option
and can leave the drive configured as it was shipped from the
factory.
ST31250ND and ST32550ND drives should be configured with a jumper
connecting J1 pins 1 and 3 (and no jumper on J1 pins 2 and 4).
J4 Synchronizing spindles N/ND Models
-------------------------------------
+ Spindle Sync Reference
---+-----+---------------+-
| 2 o * o o o o o o o | (Front View)
| 1 o * o o o o o o o |J4
+-----+---------------+
+ Spindle Sync Ground
If you are installing two or more Barracuda drives, you may
(optionally) synchronize their spindles to reduce the latency
associated with switching from one drive to another. Spindle sync
cables are used to connect the drives.
After connecting each drive with spindle sync cables, designate a
master spindle sync reference source. This master source is normally
a disc drive located on the same SCSI bus as the other drives you
want to synchronize with. To designate a drive as the master, use
SCSI interface commands.
Synchronizing spindles WC Models
--------------------------------
Spindle synchronization for WC drives is normally handled on the
SSCI bus by the host system using connector contact 37 for the
spindle sync reference signal. System designers may, optionally,
install a spindle sync cable using pin 6 on the J4 connector to
provide +SSREF.
+-- Spindle Sync Reference
++--J5------1 Power
|o o o o o o| XXXXXXXX
|o o o o o o| XXXXXXXX
++----------+
+-- Spindle Sync Ground
J4 RESERVED
-----------
---+---------------------+-
| x o o o o o x x x x | (Front View)
| x o o o o o x x x x |J4 x = RESERVED
+---------------------+
J4 Remote LED
-------------
+- GND (Cathode)
---+---+-----------------+-
| 2 o o o o o o o o o | (Front View)
| 1 o o o o o o o o o |J4
+---+-----------------+
+- POS (Anode)
NOTE
Note to subsystem designers: In Europe, a red LED indicates an error
or warning condition. For this reason, you may want to use a color
other than red with this connection.
J2 Other applicable jumper options N/ND Models
====================================================================
---+-------------------+-
| x x o o o o x x x | (Front View)
| x x o o o o x x x |J2 x = RESERVED
+-------------------+
Parity Check Option
-------------------
---+-------------------+-
| 2 o * o o o o o o | Enables parity check of SCSI bus
| 1 o * o o o o o o |J2 (DEFAULT)
+-------------------+
---+-------------------+-
| 2 o X o o o o o o | Diables parity check
| 1 o X o o o o o o |J2
+-------------------+
Write Protect Option
--------------------
---+-------------------+-
| 2 o o * o o o o o | Write Protect Disabled (Default)
| 1 o o * o o o o o |J2 Enable writing
+-------------------+
---+-------------------+-
| 2 o o X o o o o o | Write Protect Enabled
| 1 o o X o o o o o |J2 Drive is write protected!
+-------------------+
Motor Start Option
------------------
---+-------------------+-
| 2 o o o X o o o o | Enable motor start. The drive waits for
| 1 o o o X o o o o |J2 the Start Unit command from host before
+-------------------+ starting the spindle motor.
---+-------------------+-
| 2 o o o * o o o o | Disable motor start (default). The
| 1 o o o * o o o o |J2 drive starts according to the Delay
+-------------------+ Motor Start option.
Delay Motor Start Option
------------------------
Delay Motor Start option (valid only if the Motor Start jumper is
not connected)
---+-------------------+-
| 2 o o o o * o o o | Disable the Delay Motor Start option.
| 1 o o o o * o o o |J2 DEFAULT
+-------------------+
---+-------------------+-
| 2 o o o o X o o o | Motor start delay equal to the SCSI ID
| 1 o o o o X o o o |J2 multipled by 10 seconds. For example, if
+-------------------+ the SCSI ID = 2, the drive starts in 20
seconds.
REAR VIEW
50 pin I/O Cable Connection
| POWER
+------------------------1+ /---------\ TOP (HDA)
-+:::::::::::::::::::::::::+-+ O O O O +---------
+-------------------------+ +-5-G-G-12+ BOTTOM
These pins not on differential --> (o o) back
model ND +------ o o
| o o front
| 2 1
|
+- J1 Terminator options -+- (single-ended) -----------+
| o o o o o o o o xxx |
| o o o x x o x x o o |
| xxx o X X o X X o o |
| 2 1 2 1 2 1 2 1 2 1 |
| A B C D E |
+------------------------------------------------------+
A - Term. power from drive (default)
B - Term. power to SCSI bus (only option available for differential
ND)
C - Term. power from SCSI bus
D - Term. power to SCSI bus and drive
E - Enable SCSI terminator (jumper on pins 5-6)
RIGHT SIDE VIEW (ST-31250N)
BACK +-+ J2 123456789 TOP (HDA) FRONT
OF I/O+---------------------P-W-A----------------------- OF
DRIVE +-+ ::::::::: BOTTOM DRIVE
|||||||||
1-2 RESERVED --++||||+++-- RESERVED 7-9
3 Parity Disable ----+||+----- Delay Motor Start 6
4 Write Protect -----++------ Motor Start Enable 5
FRONT VIEW (ST-31250N)
J4
TOP (HDA) +----------1
---P-W-A---------------------+::::::::::+-------
++++++++++++
BOTTOM ||||||||||
||||||||||
RESERVED -++++|||||+- RESERVED
ID 4 -----+|||+-- Remote LED (pin-3 +5V)
ID 2 ------+|+--- Spindle Synchronization
ID 1 -------+ (pin-6 REF SIG+)
Enabling write cache
--------------------
Write caching is a feature that allows the drive to transfer write
data to its own cache, tell the controller that the task is complete,
and then actually complete the write at a later time. This improves
write performance by freeing the CPU to go on to its next command.
WARNING
Information can be lost is you enable write cache and there is a
system failure (for example, power failure) before the data has
actually been physically written to the disc.
OEM drives are shipped with write cache disabled by default. If
you want to enable the write cache, refer to your system's drive
controller and software utility documentation. Seagate provides an
ASPI utility that you can use in a PC compatible system to enable
the write cache.
**********************************************************************
I N S T A L L
**********************************************************************
SEAGATE ST31250/32550N/ND/W/WD/WC/DC INSTALL. GUIDE 83328920, REV. E
Notes on installation
=====================
Installation direction
----------------------
horizontally vertically
+-----------------+ +--+ +--+
| | | +-----+ +-----+ |
| | | | | | | |
+-+-----------------+-+ | | | | | |
+---------------------+ | | | | | |
| | | | | |
| | | | | |
+---------------------+ | +-----+ +-----+ |
+-+-----------------+-+ +--+ +--+
| |
| |
+-----------------+
The drive will operate in all axis (6 directions).
Mounting the drive and connecting cables
----------------------------------------
Do not touch the connector pins or any components on the control
board without observing static-discharge precautions. Always handle
the drive by the frame only.
The drive may be mounted in any orientation (horizontally,
vertically, and any combination thereof); however, you must ensure
that the drive receives adequate air flow for cooling.
1. Mount the drive to the host system's chassis using four 6-32
UNC screws. Two mounting holes are in each side of the drive
and there are four mounting holes in the bottom of the drive.
The maximum length that the screws should extend into the chassis
mounting holes is 0.15 inch (3.81 mm), measured from the outer
surface of the chassis. Tighten the screws down evenly. Do not
overtighten or force the screw if it does not seem to screw in
easily, because this means the threads are not properly aligned.
In this case, back the screw out and try again.
2. Verify that all connections between the drive and the host system
are correctly installed.
3. Verify that you have correctly installed jumpers.
4. Connect the 50-pin SCSI cable into the drive's SCSI connector.
Take care not to stretch or crimp this cable, and do not block
the system's cooling air flow with the cable.
The drive receives DC power through a 4-pin connector mounted next
to the SCSI connector. The output of a power supply must meet SELV
(safety extra low voltage) as defined in IEC 950. To connect the
DC power cable to the drive, insert the cable end into the drive's
DC power connector.
NOTE
Signal ground on the power control board (PCB) and the head and
disc assembly (HDA) are connected together in this drive and you
cannot separate them. The equipment in which you have mounted the
drive is connected directly to the HDA and PCB without electrically
isolating shock mounts. Maximizing the conductive contact area
between HDA ground and system ground may reduce radiated emissions.
If you do not want the system chassis to be connected to the HDA/PCB
ground, you must provide a nonconductive (electrically isolating)
method of mounting the drive in the host system. This may increase
radiated emissions and is the system designer's responsibility.
5. Replace the host system's cover.
This mounting procedure does not apply to WC or DC model drives!
To mount a WC or DC drive, plug the drive into the system's single
connector attachment (SCA) position on the system's back panel.
Providing adequate cooling
--------------------------
The enclosure design must ensure adequate cooling for the drive.
The maximum ambient temperature is 50*C.
We recommend orienting the drive or directing the air flow in a
way that creates the least amount of air-flow resistance while
providing air flow above the circuit boards and around the head and
disc assembly (HDA). Also, choose the shortest possible path between
the air inlet and exit. This minimizes the distance traveled by air
that is heated by the drive and by other nearby heat sources.
DC Power
--------
+-----J3-----+ pin 1 +12 VDC
| 4 3 2 1 | pin 2 +12 Volts Return
+------------+ pin 3 + 5 Volts Return
pin 4 + 5 VDC
**********************************************************************
F E A T U R E S
**********************************************************************
SEAGATE ST31250/32550N/ND/W/WD/WC/DC INSTALL.GUIDE 83328920, REV. E
Preface
-------
This manual contains information for users of the Seagate ST31250
and ST32550 Barracuda 2LP SCSI disc drives. It provides support
services, performance specifications, and initial setup information.
Additional information is available in the Barracuda 2LP Product
Manual (part number 83328930). Contact your Seagate sales
representative if you need to order this publication.
Electrostatic discharge protection
----------------------------------
Caution.
Removal of circuit boards by personnel not performing depot
repair will damage components and may void the warranty.
All drive electronic assemblies are sensitive to static electricity,
due to the electrostatically sensitive devices used within the drive
circuitry. Although some devices such as metaloxide semiconductors
are extremely sensitive, all semiconductors, as well as some
resistors and capacitors, may be damaged or degraded by exposure
to static electricity.
Electrostatic damage to electronic devices may be caused by the
direct discharge of a charged conductor or by exposure to the
static fields surrounding charged objects. To avoid damaging drive
electronic assemblies, observe the following precautions when
installing or servicing the drive:
- Ground yourself to the drive whenever the drive electronics are
or will be exposed. Connect yourself to ground with a wrist strap
(Seagate part number 12263496). Connection may be made to any
grounded metal assembly. As a general rule, remember that you and
the drive electronics must all be grounded to avoid potentially
damaging static discharges.
- Turn off the power before removing or installing the DC power
cable.
- Do not remove any circuit boards from the drive.
- Never use an ohmmeter on any circuit boards.
- When installing the drive on a carrier or tray, discharge the
static electricity from the carrier or tray prior to inserting it
into the system.
Important safety information and precautions
--------------------------------------------
Caution. Use forced-air ventilation when bench testing the drive to
ensure proper cooling of drive components.
Use proper safety and repair techniques for safe, reliable operation
of this unit. Service should be done only by qualified persons.
The procedures in this manual and labels on the unit contain warnings
and cautions that must be carefully read and followed to minimize or
eliminate the risk of personal injury. The warnings point out condi-
tions or practices that may endanger you or others. The cautions
point out conditions or practices that may damage the unit, possibly
making it unsafe for use.
Always observe the following warnings and precautions:
- Perform all maintenance by following the procedures in this manual.
- Follow all cautions and warnings in the procedures.
- Use sound safety practices when operating or repairing the unit.
- Use caution when troubleshooting a unit that has voltages present.
Turn off power to the unit before servicing it.
- Wear safety shoes when removing or replacing heavy parts.
- Ensure that the internal temperature of the rack or cabinet does
not exceed the limits defined for the drive when the drive is
mounted in an equipment rack or cabinet. When units are stacked
vertically, pay special attention to the top where temperatures
are usually highest.
- Do not remove any circuit boards from the drive chassis. Return
the entire drive for depot repair if any circuit board is
defective. Removal of circuit boards by personnel not performing
depot repair will damage components and may void the warranty.
- Do not remove the head and disc assembly (HDA) from the drive
chassis. Return the entire drive for depot repair if the HDA is
defective.
- Do not attempt to disassemble the HDA. It is not field repairable.
If the sealed HDA is opened by personnel not performing depot
repair, this will damage compo-nents and void the warranty.
As a component, this drive is designed to be installed and operated
in accordance with UL1950, IEC950, EN60950, CSA C22.2 950, and
VDE0805.
Typical applications of these disc drives include customer packag-
ing and subsystem design. Safety agencies conditionally certify
component assemblies, such as the Barracuda disc drive, based on
their final acceptability in the end-use product. The subsystem
designers are responsible for meeting these conditions of accept-
ability in obtaining safety, regulatory agency compliance in their
end-use products and for certifying where required by law. A
necessary part of meeting safety requirements is the provision
for overcurrent protection on drive SELV supply voltages.
This unit is a component part and as such is not meant to comply
with FCC or similar national requirements as a standalone unit.
Engineering radiated emissions test results are available through
the Seagate Safety Department to assist the subsystem designer.
General description
-------------------
Barracuda 2LP SCSI disc drives are high-speed, randomaccess digital-
data storage devices.
The drive is a component for installation in an enclosure designed
for the drive. This is often a rack within the system or an external
enclosure designed to house one or more disc drives or other
peripheral units. In either case, the disc drive must receive
adequate cooling and it must be sufficiently grounded and
shielded from emissions. The Barracuda 2LP Product Manual (part
number 83328930) contains guidelines for a properly designed
enclosure.
**********************************************************************
G E N E R A L
**********************************************************************
SEAGATE SCSI
Interface requirements
----------------------
How to use this interface manual
This specification is designed to provide a universal detailed
description of the SCSI interface for those disc drive products whose
Product Manuals (Volume 1) do not contain the details of how the
SCSI interface is implemented by that drive.
Note: Volume 1 Product Manuals have tables in Section 11 that specify
which SCSI-1 or SCSI-2/SCSI-3 features they implement, what the
default parameters are for the various features they implement and
which parameters are changeable and which are not. No method exists
at present to inform an initiator if a target supports "SCSI-3"
features as opposed to only SCSI-2 features. A few "SCSI-3" features
are supported by Seagate drives, but no attempt has been made herein
to differentiate between SCSI-2 and "SCSI-3" features. Therefore,
when an Inquiry command reports what the ANSI approved version of the
drive is, it reports either SCSI-1 or SCSI-2, where "SCSI-2" means
SCSI-2 features plus some "SCSI-3" features.
No attempt is made in this universal specification to specify which
descriptions or tables apply to SCSI-1 and which to SCSI-2 or SCSI-3.
The combination of this general specification with the details in
the Section 11 tables of the individual drive Product Manual (Volume
1) provides a description of the individual drive implementation of
the SCSI interface. This interface manual is not intended to be
stand-alone text on SCSI-1 or SCSI-2/SCSI-3 features.
Reference must be made back to the individual drive Product Manuals
to find out what are SCSI-1 and what are SCSI-2/SCSI-3 features.
This specification is Volume 2 of a set of manuals that is made up of
separate drive Product Manuals (Volume 1) and this manual. This
Volume 2 Manual is referenced by other Volume 1 Product Manuals
representing the drives listed below.
Product Manuals for the following models reference this volume:
ST11200N/ND/NC, ST1980N/ND/NC, ST1830N, ST1950N, ST3500N, ST3600N,
ST3610N/ND/NC, ST12400N/ND/NC, ST12400 Wide, ST11900N/ ND/NC,
ST31200N/ND/NC, ST31200 Wide, ST11950N/ND, ST11950W/WD,
ST12450W/WD, ST12550N/ND, ST12550W/WD, ST15150N/ND, ST15150W/WD,
ST3655N, ST3550W, ST3390N and ST3285N, ST32430N/ND/NC,
ST32430W/WD/WC, ST15230N/ND/NC, ST31250N/ND, ST31250W/WD/WC,
ST32151N, ST31051N, ST32550N/ND, ST32550W/WD/WC, ST3471N,
ST410800N/ND, ST410800W/WD.
General interface description
-----------------------------
This Product Manual describes the Seagate Technology, Inc. subset of
the SCSI (Small Computer Systems Interface) as implemented on the
Seagate built disc drives listed above. The interface is compatible
with the SCSI Interface Specifications of the ANSI SCSI-1 standard,
the ANSI SCSI-2 Standard and the common command set (CCS) document,
Revision 4.B. The disc drives covered by this Product Manual are
classified as "Intelligent" peripherals.
The Seagate SCSI interface described herein consists of a 9 or 18 bit
bidirectional bus (8 data + 1 parity or 16 data + 2 parity) plus 9
control signals supporting multiple initiators, disconnect/
reconnect, self configuring host software, automatic features that
relieve the host from the necessity of knowing the physical
architecture of the target (logical block addressing is used), and
some other miscellaneous features.
The SCSI physical interface uses either single ended drivers and
receivers or differential drivers and receivers and uses asynchronous
or synchronous communication protocols. The bus interface transfer
rate for asynchronous or synchronous is given in individual disc
drive Volume 1 Product Manuals. The bus protocol supports multiple
initiators, disconnect/reconnect, additional messages plus 6 byte and
10 byte Command Descriptor Blocks. Unless specified otherwise in the
individual drive Product Manuals (Vol. 1), the disc drive is always a
target, and never an initiator. For certain commands, which may or
may not be supported by a particular drive model, the drive must act
as an initiator, but does not otherwise do so. For purposes of this
specification, "disc drive" may be substituted for the word "target"
wherever "target" appears.
GLOSSARY
--------
Arbitration - SCSI bus phase wherein SCSI devices try to gain control
of the SCSI bus to operate as an initiator or target
Byte - This term indicates an 8 bit hexadecimal construction.
Command Descriptor Block (CDB) - The structure used to communicate
requests from an initiator to a target.
Connect - The function that occurs when an initiator selects a target
to start an operation.
Disconnect - The function that occurs when a target releases control
of the SCSI bus, allowing it to go to the Bus Free phase.
FRU (Field Replaceable Unit) - An assembly that is believed faulty
based on test results. A value of 00h indicates an unknown cause or
the end of a list of known possible causes. Nonzero values have
product unique meanings.
Initiator - A SCSI device (usually a host system) that requests an
operation to be performed by another SCSI device.
Intermediate Status - A status code sent from a target to an
initiator upon completion of each command, except the last command,
in a set of linked commands.
I/O Process - An I/O process consists of one initial connection and
zero or more reconnections, all pertaining to a single command or
group of linked commands. More specifically, the connection(s)
pertain to a nexus as defined below in which one or more command
descriptor blocks are usually transferred. An I/O process begins with
the establishment of a nexus. An I/O process normally ends with the
BUS Free phase following successful transfer of a COMMAND COMPLETE,
ABORT, ABORT TAG, or CLEAR QUEUE message. An I/ O process also ends
when a hard RESET condition occurs, an unexpected BUS FREE phase
occurs, or when the BUS FREE phase occurs following a BUS DEVICE
RESET message.
I T nexus - A nexus prior to the successful receipt of an IDENTIFY
message, at which time the nexus is changed to an I T L nexus. (See
glossary word "Nexus").
I T L nexus - A nexus that exists between an initiator and a Logical
Unit. This relationship replaces the prior I T nexus. (See glossary
word "Nexus").
I T L Q nexus - A nexus between an initiator, a Logical Unit, and a
queue tag following the successful receipt of one of the QUEUE
messages. This relationship replaces the prior I T L nexus. (See
glossary word "Nexus").
Logical Unit - A physical device or virtual device addressable
through a target. The disc drive is a target but also a Logical Unit.
Logical Unit Number - An encoded three bit identifier for the logical
unit. The disc drive is considered Logical Unit number zero.
LSB - Least significant byte
MSB - Most significant byte
ms - millisecond
LUN - Logical unit number
mm - Millimetre
SCSI bus
--------
This manual discusses only the "logical" and timing characteristics
of the SCSI system and interface. The SCSI bus physical
characteristics (voltages, connector configurations, pinouts, etc.)
are given in the individual disc drive Product Manuals (Volume 1)
Section "Interface requirements", which covers all of the interface
requirements and SCSI features supported by the drive described in
the particular Product Manual being referenced.
Communication on the SCSI Bus is allowed between only two SCSI
devices at a time. Some Seagate drives support systems with a maximum
of eight SCSI devices including the host computer(s) connected to the
SCSI bus. Some Seagate drives support systems with a maximum of
sixteen SCSI devices on the SCSI bus. Each SCSI device has a SCSI ID
Bit.
The SCSI ID is assigned by installing from 0 to 3 (8 device systems)
jumper plugs or 0-4 (16 device systems) jumper plugs onto a connector
in a binary coded configuration during system configuration. Some
drive models have an interface that includes the SCSI bus ID lines,
so that the host can set the drive ID over the interface. See
individual disc drive Product Manual, Section "Option/configuration
headers".
When two SCSI devices communicate on the SCSI Bus one acts as an
initiator and the other acts as a target. The initiator (typically a
host computer) originates an operation and the target performs the
operation. The disc drive always operates as a target, unless
specified otherwise (i.e., certain commands are supported) in the
individual drive Product Manual.
The Host Adapter/Initiator must be identified by one of the eight
SCSI Device Addresses. Make sure that none of the devices on the SCSI
bus have duplicate addresses. Certain SCSI bus functions are assigned
to the initiator and certain SCSI bus functions are assigned to the
target. The initiator will select a particular target. The target
will request the transfer of Command, Data, Status or other
information on the data bus.
Information transfers on the data bus are interlocked and follow a
defined REQ/ACK Handshake protocol. One byte of information will be
transferred with each handshake. Synchronous data transfers do not
require a one for one interlocking of REQ/ACK signals, but the total
number of REQ pulses in a particular data transfer event must equal
the total number of ACK pulses.
The disc drive supports single initiator, single target; single
initiator, multiple target; multiple initiator, single target; or
multiple initiator, multiple target bus configurations.
SCSI bus signals
----------------
There are ten control and eighteen data signals, as listed below:
- BSY
- C/D
- MSG
- DIFFSENS
- SEL
- I/O
- REQ
- DB(7-0, P); DB(15-8,P1)
- ACK
- ATN
- RST
Some drive models have a single 80 pin I/O connector that contains
additional interface lines that carry drive configuration select
signals. These are peculiar to certain drives and are not SCSI
standard signals. These are described in the drive model's Volume 1
Product manual, but not here. The 28 SCSI standard signals are
described as follows:
BSY (Busy) - An "OR-tied" signal to indicate the bus is being used.
SEL (Select) - A signal used by an initiator to select a target, or
by a target to reselect an initiator.
C/D (Control/Data) - A signal driven by a target to indicate whether
Control or Data information is on the Data Bus. Assertion indicates
Control.
I/O (Input/Output) - A signal driven by a target to control the
direction of data movement on the Data Bus with respect to an
initiator. Assertion indicates input to the initiator. This signal
also distinguishes between Selection and Reselection phases.
MSG (Message) - A signal driven by a target during the Message phase.
REQ (Request) - A signal driven by a target to indicate a request for
REQ/ACK data transfer handshake.
ACK (Acknowledge) - A signal driven by an initiator to indicate an
acknowledgment for a REQ/ACK data transfer handshake.
ATN (Attention) - A signal driven by an initiator to indicate the
Attention condition. It is used to request to send a message out to
the target. If an initiator asserts ATN while asserting SEL it
indicates to the target that the initiator supports messages other
than command complete.
RST (Reset) - An "OR-tied" signal that indicates the Reset condition.
DIFFSENS (Differential Sense) - When the drive has differential SCSI
I/O circuits, the DIFFSENS signal disables the drive s differential
driver/receiver circuits if the SCSI I/O cable is plugged in upside
down, or if a single-ended SCSI I/O cable is plugged into a
differential I/O drive. Disabling the differential I/O drivers/
receivers is necessary to prevent burning them out if a grounded I/O
line is connected to any of the differential circuit outputs, which
are at a positive voltage (+2 V or +3 V) when not disabled.
DB(7-0,P) and DB(15-8,P1)
(Data Bus) - Sixteen data bit signals, plus parity bit signals form a
Data Bus. DB(7) is the most significant bit and has the highest
priority during the Arbitration phase (on both eight and sixteen
device systems). Bit number significance, and priority decrease
downward to DB(0), and then from DB15 down to DB8 (DB0 is higher than
DB15). A data bit is defined as one when the signal is asserted and
is defined as zero when the signal is negated.
Data parity DB(P) and DB(P1) is odd - The use of parity is a system
option. The disc drive always checks parity on the data bits, but has
the capability to enable/disable parity error reporting to the host.
See configuration selection in the applicable Product Manual. Parity
checking is not valid during the Arbitration phase.
Greater detail on each of the SCSI Bus signals is found in the
following sections.
Drive Select
------------
For SCSI ID selection install drive select jumpers as shown in
configuration selection figure in applicable Product Manual. Refer to
section 10 of the individual drive Product Manual for the location
of the drive select header. The disc drive using the eight bit data
interface can have one of eight ID bits selected by installing 0 to 3
jumpers in a binary coded configuration on the drive select header.
Drives using the 16 bit data interface can have one of sixteen ID
bits selected by installing 0 to 4 jumpers in a binary coded
configuration on the drive select header.
Signal Values
-------------
Signals may assume true or false values. There are two methods of
driving these signals. In both cases, the signal shall be actively
driven true, or asserted. In the case of OR-tied drivers, the driver
does not drive the signal to the false state, rather the bias
circuitry of the bus terminators pulls the signal false whenever it
is released by the drivers at every SCSI device. If any driver is
asserted, then the signal is true. In the case of non-OR-tied
drivers, the signal may be negated. Negated means that the signal may
be actively driven false, or may be simply released (in which case
the bias circuitry pulls it false), at the option of the implementor.
OR-Tied signals
---------------
The BSY and RST signals shall be OR-tied only. In the ordinary
operation of the bus, these signals are simultaneously driven true by
several drivers. No signals other than BSY, RST, and DB(P) are
simultaneously driven by two or more drivers, and any signal other
than BSY and RST may employ OR-tied or non-OR-tied drivers. DB(P)
shall not be driven false during the Arbitration phase. There is
no operational problem in mixing OR-tied and non-OR-tied drivers on
signals other than BSY and RST.
Signal sources
--------------
All SCSI device drivers that are not active sources shall be in the
passive state. Note that the RST signal may be sourced by any SCSI
device at any time. The disc drive functions as a target.
Nonarbitrating system
---------------------
In systems with the Arbitration phase not implemented, the initiator
shall first detect the Bus Free phase and then wait a minimum of a
bus clear delay. Then, except in certain single initiator
environments with initiators employing the single initiator option
the initiator shall assert the desired target's SCSI ID and its own
initiator SCSI ID on the Data Bus. After two deskew delays, the
initiator shall assert SEL.
Arbitrating systems
-------------------
In systems with the Arbitration phase implemented, the SCSI device
that won the arbitration has both BSY and SEL asserted and has
delayed at least a bus clear delay plus a bus settle delay before
ending the Arbitration phase. The SCSI device that won the
arbitration becomes an initiator by releasing I/O. Except in certain
single initiator environments with initiators employing the single
initiator option, the initiator shall set the Data Bus to a value
which is the OR of its SCSI ID bit and the target s SCSI ID bit. The
initiator shall then wait at least two deskew delays and release
BSY. The initiator shall then wait at least a bus settle delay before
looking for a response from the target.
All systems
-----------
In all systems, the target shall determine that it is selected when
SEL and its SCSI ID bit are true and the BSY and I/O signals are
false for at least a bus settle delay. The selected target will
examine the Data Bus in order to determine the SCSI ID of the
selecting initiator unless the initiator employed the single
initiator option. The selected target shall then assert BSY within a
selection abort time of its selection; this is required for correct
operation of the timeout procedure. In systems with parity
implemented, the target shall not respond to a selection if bad
parity is detected. Also, if more than two SCSI ID bits are on the
Data Bus, the target shall not respond to selection. At least two
deskew delays after the initiator detects BSY is asserted, it shall
release SEL and may change the Data Bus.
Single initiator option
-----------------------
Initiators that do not implement the Reselection phase, and do not
operate in the multiple initiator environment, are allowed to set
only the target's SCSI ID bit during the Selection phase. This makes
it impossible for the target to determine the initiator s SCSI ID.
Selection time out procedure
----------------------------
A Selection timeout procedure is specified for clearing the SCSI bus.
If the initiator waits a minimum of a selection timeout delay and
there has been no BSY response from the target, the initiator shall
continue asserting SEL and shall release the Data Bus. If the
initiator has not detected BSY to be asserted after at least a
selection abort time plus two deskew delays, the initiator shall
release SEL allowing the SCSI bus to go to the Bus Free phase. SCSI
devices shall ensure when responding to selection that the selection
was still valid within a selection abort time of their assertion of
BSY. Failure to comply with this requirement could result in an
improper selection (two targets connected to the same initiator,
wrong target connected to an initiator, or a target connected to no
initiator). The disc drive supports systems that implement this
procedure.
Asynchronous information transfer
---------------------------------
The target shall control the direction of information transfer by
means of the I/O signal. When I/O is true, information shall be
transferred from the target to the initiator. When I/O is false,
information shall be transferred from the initiator to the target.
If I/O is true (transfer to the initiator), the target shall first
drive DB(7-0,P)* to their desired values, delay at least one deskew
delay plus a cable skew delay, then assert REQ. DB(7-0,P)* shall
remain valid until ACK is true at the target. The initiator shall
read DB(7-0,P)* after REQ is true, then signal its acceptance of the
data by asserting ACK. When ACK becomes true at the target, the
target may change or release DB(7-0, P)* and shall negate REQ. After
REQ is false the initiator shall negate ACK. After ACK is false, the
target may continue the transfer by driving DB(7-0,P)* and asserting
REQ, as described above.
If I/O is false (transfer to the target) the target shall request
information by asserting REQ. The initiator shall drive DB(7-0,P)* to
their desired values, delay at least one deskew delay plus a cable
skew delay and assert ACK. The initiator shall continue to drive the
DB(7-0,P)* until REQ is false.
When ACK becomes true at the target, the target shall read
DB(7-0,P)*, then negate REQ. When REQ becomes false at the initiator,
the initiator may change or release DB(7-0,P)* and shall negate
ACK. The target may continue the transfer by asserting REQ, as
described above.
Synchronous data transfer
-------------------------
Synchronous data transfer may be used only in the data phase if
previously agreed to by the initiator and target through the message
system. The messages determine the use of synchronous mode by both
SCSI devices and establish a REQ/ACK offset and a transfer period.
The REQ/ACK offset specifies the maximum number of REQ pulses that
can be sent by the target in advance of the number of ACK pulses
received from the initiator, establishing a pacing mechanism. If
the number of REQ pulses exceeds the number of ACK pulses by the
REQ/ACK offset, the target shall not assert REQ until the next ACK
pulse is received. A requirement for successful completion of
the data phase is that the number of ACK and REQ pulses be equal.
The target shall assert the REQ signal for a minimum of an assertion
period. The target shall wait at least the greater of a transfer
period from the last transition of REQ to true or a minimum of a
negation period from the last transition of REQ to false before
asserting the REQ signal.
The initiator shall send one pulse on the ACK signal for each REQ
pulse received. The ACK signal may be asserted as soon as the leading
edge of the corresponding REQ pulse has been received. The initiator
shall assert the ACK signal for a minimum of an assertion period. The
initiator shall wait at least the greater of a transfer period from
the last transition of ACK to true or for a minimum of a negation
period from the last transition of ACK to false before asserting the
ACK signal.
Unit attention condition
------------------------
The disc drive sets up the Unit Attention condition when it stores
(within itself) a Unit Attention condition flag for each device on
the SCSI bus having an initiator relationship with the disc drive,
and this Unit Attention condition persists for each initiator until
the condition is cleared (flag negated) by each initiator
individually. The Unit Attention condition results when one of the
following events occur:
1. A power-on sequence occurs.
2. A reset is generated internally by the disc drive (caused by a
power glitch).
3. A Bus Device Reset message causes the disc drive to reset itself.
4. The RESET I/O line resets the disc drive.
5. An initiator changes one or more of the Mode Select parameters in
the disc drive (these changes could affect one or more of the
other initiators).
6. The inquiry data has been changed.
7. The mode parameters in effect for an initiator have been restored
from nonvolatile memory.
8. An event occurs that requires the attention of the initiator.
9. A Clear Queue message received.
10. The Log parameters are changed. Unit Attention Condition is
posted for all initiators in the system other than the one
that changed the Log Parameters.
The Unit Attention Parameters page (page 00h, bit 4 of byte 2) of the
Mode Select Command controls whether or not a Check Condition Status
is to be reported to affected initiators when a Unit Attention
condition exists. The Unit Attention condition for a particular
initiator is cleared when that initiator does one of the following:
1. It sends a Request Sense Command.
2. It sends any other legitimate command, with the exception
of the Inquiry command. The Inquiry command does not clear the
Unit Attention condition.
When a Unit Attention condition flag is stored in the disc drive
for an initiator, the commands that initiator issues to the disc
drive operate as described in the following paragraphs.
If an initiator sends an Inquiry command to the disc drive when the
disc drive has stored a Unit Attention condition flag for that
initiator before or after the disc drive reports Check Condition
status), the disc drive shall perform the Inquiry command and shall
not clear the Unit Attention condition.
If an initiator sends a Request Sense command to the disc drive when
a Unit Attention condition flag is stored for that initiator (before
or after the disc drive reports Check Condition), the disc drive
shall discard any pending sense data, report the Unit Attention Sense
Key, and clear the Unit Attention condition (negate the flag) for
that initiator.
If an initiator issues a command other than Inquiry or Request Sense
while a Unit Attention condition flag is stored for that initiator,
the disc drive may or may not perform the command and report Check
Condition status, depending on whether or not the Unit Attention bit
is zero or one in the Unit Attention Mode Parameters page (Page 00h,
bit 4 of byte 2). If a Request Sense is issued next, the Unit
Attention condition is reported and cleared (flag negated) as noted
in the preceding paragraph. If another command other than Request
Sense or Inquiry is issued instead, the disc drive shall perform the
command and return the appropriate status. The Unit Attention
condition for the subject initiator is cleared (flag negated) and the
sense data and flag indicating there has been a Unit Attention
condition are lost.