S T 3 6 0 0 N SEAGATE NO MORE PRODUCED Native| Translation ------+-----+-----+----- Form 3.5"/SLIMLINE Cylinders 1877| | | Capacity form/unform 525/ 600 MB Heads 7| | | Seek time / track 11.0/ 2.0 ms Sector/track | | | Controller SCSI2 SI/FAST Precompensation Cache/Buffer 256 KB SEGMENTED Landing Zone Data transfer rate 4.000 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 5.5 W Shock g 10 | 75 seek 7.0 W Rotation RPM 4500 read/write W Acoustic dBA spin-up W ECC Bit MTBF h 200000 Warranty Month 24 Lift/Lock/Park YES Certificates CSA,FCC,IEC950,UL1950,VDE
SEAGATE ST3600N/ND FAMILY INSTALLATION GUIDE 77738481, REV. A
+---------------------------------------------------------+ |1-+ +------1 J5 |XX || |J6 +------+ |XX SCSI |+-+ +1 |XX I/O | || |XX | || |XX | I/O ++ |XX | Terminators++ |XX | || |XX | || |XX | ++ |XX | ++ |XX | || |XX | || |XX | ++ |X1 | | | +---------1 J2 |XX Power | +---------+ |XX +---------------------------------------------------------+
SEAGATE ST3600N/ND FAMILY INSTALLATION GUIDE 77738481, REV. A
Each disk drive has one or more option select header connectors on
the back, side or front where jumper plugs are installed to select
the way that the drive is to be configured or to select its ID on the
J2 Motor Start/Write Protect/Terminator Power
+-1--2--3--4--5--6--7--8-+ | o X o o o o o 1 | | o X o o o o xxxx | +----+-------------------+ \ Position A Position 2
1 for Factory use only.
2 Jumper installed in position 2 enables the Delayed Motor Start option (if jumper in position 3 is off). Motor start delays is 12 times the drive ID number in seconds; i.e. drive ID 0 starts immediately. drive one starts 12 seconds later, etc. Not factory installed.
3 Jumper installed enables Motor Start option. The drive waits for the Start unit command from the host before starting the spindle motor. If no jumper is installed, drive operation de- pends on whetheror not there is a jumper in position 2. Not factory installed.
If jumpers 2 and 3 are both off, drive spins up with no delay when power is applied.
4 Jumper installed means entire drive is write protected. Not factory installed.
5 Jumper installed means parity checking by the drive is enabled. Not factory installed.
6 Reserved for later use.
7 Select terminator power source. In position 8 the drive 8 supplies power to the SCSI bus, pin 26. In position 7 drive supplies power only to its own terminators. (Factory setting) Jumper horizontally between positions 7 and 8 (position A) means the drive takes power from the SCSI bus, pin 26. Jumpers installed on both 7 and 8 at same time is allowed. Default is jumper on position 7.
J5 SCSI ID ---------- SCSI ID 0 SCSI ID 1 SCSI ID 2 +---------+ +---------+ +---------+ | o o 1 | | X o o | | o X o | | o o o | | X o o | | o X o | A +-0--1--2-+ +---------+ +---------+
SCSI ID 3 SCSI ID 4 SCSI ID 5 +---------+ +---------+ +---------+ | X X o | | o o X | | X o X | | X X o | | o o X | | X o X | +---------+ +---------+ +---------+
SCSI ID 6 SCSI ID 7 +---------+ +---------+ | o X X | | X X X | | o X X | | X X X | +---------+ +---------+
Drive ID on SCSI Bus (J6 may be used instead). The drive ID is binary
J6 SCSI ID (optional)
A A A SCSI ID 0 +-2--1--0----------+ +------------------+ | o o o o o 1 | | o o o o o o | | o o o o o o | | o o o o o o | +-1--2--3--4--5--6-+ +------------------+
SCSI ID 1 SCSI ID 2 +------------------+ +------------------+ | o o X o o o | | o X o o o o | | o o X o o o | | o X o o o o | +------------------+ +------------------+
SCSI ID 3 SCSI ID 4 +------------------+ +------------------+ | o X X o o o | | X o o o o o | | o X X o o o | | X o o o o o | +------------------+ +------------------+
SCSI ID 5 SCSI ID 6 +------------------+ +------------------+ | X o X o o o | | X X o o o o | | X o X o o o | | X X o o o o | +------------------+ +------------------+
SCSI ID 7 Sync Spindle +------------------+ +------------------+ | X X X o o o | | o o o X o o | | X X X o o o | | o o o X o o | +------------------+ +------------------+
Remote LED +------------------+ | o o o o X o | | o o o o X o | +------------------+
1,2,3 Either J5 or J6 (optional) may be used to select drive ID. Both should not be used at same time, because at some future time, settings may be changed, causing the drive to not respond correctly. The factory installs no ID jumpers on J5 or J6 (drive ID 0).
4 Used as a cable connection for the Ref Index/+L signal for sync spindle feature.
5 Used if needed for a connection to a remote LED indicator. Pin 10 (lower row), connects in the drive to the +5 V supply. Pin 9 (closest to drive HDA), connects in the drive to ground.
On SCSI I/O drives either J6 (on the front of the drive) or J5 (on
the side behind the DC Power connector) may be used to set the drive
ID. To avoid possible incorrect ID setting, do not use both J5 and
J6 for ID selection.
SEAGATE ST3600 FAMILY INSTALLATION GUIDE 77738481, REV. A
horizontally vertically +-----------------+ +--+ +--+ | | | +-----+ +-----+ | | | | | | | | | +-+-----------------+-+ | | | | | | +---------------------+ | | | | | | | | | | | | | | | | | | +---------------------+ | +-----+ +-----+ | +-+-----------------+-+ +--+ +--+ | | | | +-----------------+
The drive may be mounted in any orientation.
Mount to host system chassis using four 6-32 UNC screws. Three
mounting holes are in each side and four in the bottom of the drive.
The maximum length that the screws should extend into the side
chassis mounting holes is 0.15 inch (3.81 mm), and 0.20 inch (5.1 mm)
into bottom holes, measured from the outer surfce of the chassis.
Tighten the screws down evenly to approximately 8 inch-Ibl. Do not
over tigthen or force when screw does not seem to screw in easily
(threads not correctly engaged).
Verify that all connections between the drive and the host system are
correctly installed. Most cables have a contrasting color stripe
indicating pin 1.
The disc drive(s) are to be installed in a customer supplied
enclosure where the surrounding air does not exceed 50* C.
Signal ground (PCB) and HDA ground are connected together in the
ST3600 drive and cannot be separated by the user. The equipment in
which the drive is mounted is connected directly to the HDA and PCB
with no electrically isolating shock mounts. If it is desired for the
system chassis to not be connected to the HDA/PCB ground, the systems
integrator or user must provide a nonconductive (electrically
isolating) method of mounting the drive in the host equipment.
SCSI interface cable connection
Models ST3600N/ND are SCSI interface drives. System connection is
via a 50-pin SCSI connector. Some cables have a contrasting color
stripe on one edge to indicate pin 1. Strain relief is recommended
at the cable. Do not block system cooling air flow in routing of
AT (IDE) interface cable connection
Model ST3600A Family drives AT (IDE) interface drive. System
connection is via a 40 pin AT (IDE) connector. Some cables have a
contrasting color strip on one edge to indicate pin 1. Use a strain
relief device at the cable. Do not block system cooling air with the
routing of cables.
Connect the AT (IDE) I/O connector cable end to drive 0 (master) and
if there is a drive 1 (slave) connect it to the connector in the
middle of the cable.
Order of locating the drives in the daisychain is not as important as
getting proper drive ID set up for the drives intended for drive 0
and drive 1.
DC Power connection
The drive receives DC power through a 4 pin connector mounted on the
PCB next to the SCSI or AT (IDE) I/O connector.
Pin 1 +12 V 2 +12 V Return 3 + 5 V Return 4 + 5 V
SCSI Resistor terminator packs
If you are installing a single drive, the resistor terminator packs
must remain installed. If you are installing multiple hard disc
drives, remove the resistor termination packs from all the drives but
the one connected to the end of the SCSI I/O cable.
When reinstalling a resisor pack, note that pin 1 end on the pack is
denoted by a dot, a number one or a notch. Usually, a square pad on
the disc drive printed wiring assembly indicates pin 1 at the socket.
Model numbers that end in "ND" have differential I/O circuits and
these drives have no provisions for terminators that plug into the
drive PCB. The system manufacturer must provide some external means
of I/O line termination.
The AT (IDE) interface drives have permanent internal I/O line
termination and do not have removable terminators.
SEAGATE ST3600 FAMILY INSTALLATION GUIDE 77738481, REV. A
Electromagnetic interference (EMI) considerations
The drive(s) described herein, as delivered, are designed for system
integration and installing into a suitable enclosure prior to use.
As such, the drive(s) described herein are supplied as a sub-assembly
and are not subject to Subpart J of Part 15 of the FCC Rules and
Regulations nor the radio Interference Regulations of the Canadian
Department of Communications.
However, the unit has been tested using proper shielding and ground-
ing and found to be compliant with the Class A limits of the FCC
Rules and the Regulations of the Canadian Department of
The power supply must satisfy the safety requirements for SELV
(Safety Extra Low Voltage) circuits.
The incorporation of the disc drives listed in this guide into a
customer enclosure must meet the appropriate safety requirements of
the country in which it is used (e.g. UL 1950, CAN/CSA-C22.2 No. 950-
M89, DIN VDE 0805/05.90 and EN 60950:1988 (IEC 950).
Low Level formatting
All ST3600 family drive models are low-level formatted at the factory
and do not require this step during installation. If an installed
drive is low-level formatted, all user data will be lost.
Partitioning and high level formatting
A drive can be sub-divided into "partitions" which behave as
individual drives within the system.
Read/Write head auto-park
Seagate disc drives described herein mentioned in this drive park the
heads automatically at power off. This feature requires no operator
Write precompensation and reduced write current
Not required on Seagate SCSI or AT (IDE) interface drives covered by
SCSI interface drives
The SCSI interface handles both drive geometry and defect management
internally. In AT systems a drive type of zero, or the "no drive
installed" option is selected for systems with SCSI drives.
All SCSI interface drives are low-level formatted at the factory. You
may wish to low-level format the drive to optimize performance for
your system. Consult the controller documentation for information on
low-level formatting. Partitioning and high-level formatting can be
done through DOS by way of the FDISK utility for partiioning, and
FORMAT for high-level formatting.
AT (IDE) interface drives
Seagate AT interface drives mimic (translate) other drive geometries.
If none of the drive types offered by the CMOS supports the number of
heads, cylinders and sectors shown by the table, and your system
does not support a "user-defined" drive type, then select a drive
type in your system CMOS with a capacity which is less than or
equal to the capacity given in the "MBytes" section of the table.
Model MBytes (F) Cylinders R/W Heads Sectors/Track
ST3600A 528 1024 16 63
ST3500A 426 895 15 62
When specifying drive geometry to the systems CMOS different values
may be used for the Cylinders, Read/Write Heads and Sectors/Track
than those given below. However, the final drive capacity shown by
the CMOS cannot exceed the capacity shown in the MBytes column of the
If your BIOS offers a "custom drive" or a "user-defined" drive type,
use one of the configurations listed in the previous table.
The CMOS calculation of drive capacity is based on a variation of the
number of bits in a megabyte, for purposes related to hexadecimal
addressing. When the drive geometry has been entered into the "user
defined" or "custom" drive type. This number should correspond with
the capacity listed in the MBytes column of the table.
Note that the drive will provide the user with full capacity as
specified in the MBytes (F) column of the table. The drive capacity
can be verified by using the CHKDSK utility provided with DOS after
the high-level formatting has been completed.
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,
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.
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
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
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
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
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
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:
- DB(7-0, P); DB(15-8,P1)
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
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
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.
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.
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.
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.
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.
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.
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
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
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
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
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.