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Hard Drive: NEC: D3856 105MB 3.5"/SL SCSI1 SE

D 3 8 5 6    NEC
NO MORE PRODUCED                                      Native|  Translation
Form                 3.5"/SLIMLINE         Cylinders    1251|     |     |
Capacity form/unform   105/  131 MB        Heads           4|     |     |
Seek time   / track  19.0/ 8.0 ms          Sector/track   41|     |     |
Controller           SCSI1 SINGLE-ENDED    Precompensation
Cache/Buffer            64 KB LOOK-AHEAD   Landing Zone
Data transfer rate          MB/S int       Bytes/Sector      512
                      1.500 MB/S ext ASYNC
Recording method     RLL 1/7                        operating  | non-operating
Supply voltage     5/12 V       Temperature *C         5 50    |    -40 60
Power: sleep              W     Humidity     %         8 80    |
       standby        1.3 W     Altitude    km            3.000|        12.000
       idle           2.6 W     Shock        g         5       |     55
       seek               W     Rotation   RPM      3456
       read/write     4.8 W     Acoustic   dBA
       spin-up            W     ECC        Bit   56
                                MTBF         h      50000
                                Warranty Month
Lift/Lock/Park     YES          Certificates


NEC D3856 THERORY OF OPERATION 806-521348-0 REV. 1 1991

  |                                                         |XX
  |                                                SW1   ++ |XXJ1
  |                                           OFF 1--+ON || |XX
  |                                               |  |   || |XX I
  |                                               4--+   || |XX N
  |                                                      ++ |XX T
  |                                         TERMINATING  ++ |XX E
  |                                         RESISTORS    || |XX R
  |                                                      || |XX F
  |                                                      || |XX A
  |                                                      ++ |XX C
  |                                                         |XX E
  |+-+LED                                                   |X1
  |+-+CONNECTOR                  JP1 JP2 JP3                |
  |   J8                           +-+-+-+                  |XXJ3
  |                                +-+-+-+                  |XX Power
  +---------------------------------------------------------+  1


NEC D3856 THEORY OF OPERATION 806-521348-0 REV. 1, 1991

Jumper Setting

x = Jumper set at factory

                                                0  1  2
                                                |  |  |
   +----------+-----------------------+     +4--3--2--1-+
   | SCSI ID  |        Jumpers        |  OFF|.  X  X  X | OPEN
   |          |   1   |   2   |   3   |  ON |X  .  .  . | CLOSED
   +----------+-------+-------+-------+     ++----------+
   |x   0     | OPEN  | OPEN  | OPEN  |      |
   |    1     | OPEN  | OPEN  | CLOSED|      Parity Check Option
   |    2     | OPEN  | CLOSED| OPEN  |
   |    3     | OPEN  | CLOSED| CLOSED|
   |    4     | CLOSED| OPEN  | OPEN  |
   |    5     | CLOSED| OPEN  | CLOSED|
   |    6     | CLOSED| CLOSED| OPEN  |
   |    7     | CLOSED| CLOSED| CLOSED|

The Unit is shipped with the SCSI address set to "0" at the factory.
When plural units are to be linked to one single SCSI bus, change the
SCSI address by the switch SW1.

 SW1  Parity Check Option
      4  OPEN   SCSI Parity Check diabled
         CLOSED SCSI Parity Check enabled

JP1 and JP2
JP1 and JP2 are used for inspection purposes at the factory. Please
refraim from touching them.

JP3 Auto Power Save
The function is selected by inserting a short-circuiting plug in JP3.

Short-circuiting plug present:
Auto power save on.

Short-circuiting plug not present:
Auto power save off.

The setting of SCSI addresses and the selection of Auto Power Save
function are read and stored at the time of reset or power-on.

The selection of the parity check On/Off function is enabled as soon
as it is set.

Setting of Optional Functions
This Unit offers two optional functions: the Auto Power Save option
to automatically put the Unit in Power Save mode when no access is
made to the HDD over a certain time period; and the other option to
select ON/OFF of the SCSI bus parity check function. The Unit comes
from the factory with the Autp Power Save option inhibited and the
parity check function set to ON.

Moreover, the short-circuiting plug to be used for setting the said
Auto Power Save function (JP3) has to be an equivalent product to the
Dupont 68905-001.

Installation/Removal of Terminating Resistors
In the case where multiple SCSI devices are to be connected to the
same SCSI bus, the terminating resistors have to be removed for all
the SCSI devices connected except for the one to be located at the
farthest end of the cable.

This Unit is shipped out of the plant with the terminating resistors
installed. Remove these terminating resistors from all the SCSI
devices but not the one which is situated at the farthest end of the


NEC D3856 THEORY OF OPERATION 806-521348-0 REV. 1, 1991

Notes on installation

Drive mounting

     horizontally             vertically
   +-----------------+   +--+             +--+ +------------------+
   |                 |   |  +-----+ +-----+  | |                  | x
   |                 |   |  |     | |     |  | x+----------------+x
 +-+-----------------+-+ |  |     | |     |  | ||x              x||
 +---------------------+ |  |     | |     |  | ||  x          x  ||
                         |  |     | |     |  | ||    x      x    ||
      x           x      |  |     | |     |  | ||      x  x      ||
 +------x------x-------+ |  +-----+ +-----+  | ||       xx       ||
 +-+------x--x-------+-+ +--+             +--+ ||     x    x     ||
   |       xx        |                         ||   x        x   ||
   |     x    x      |                         || x            x ||
   +---x--------x----+                         |x                x|
     x            x                           x++----------------++x

The D3856 Magnetic Disk Unit can be mounted horizontally as well as
vertically. In horizontal installation, mount the Unit in such a
posture that its printed-circuit board will be situated below (The
unit cannot be mounted with the interface connector J1 and the power
connector J3 positioned above or below.

The unit has 10 mounting screw holes. Use these mounting screw holes
for installing the Unit. Screws: M3x0.5, minimum depth: 4 mm

Operation of the Unit requires a SCSI bus cable and a power supply
cable. In case multiple SCSI device are going to be connected to one
single SCSI bus, it is necessary to set up their SCSI addresses and
to install/remove terminating resistors accordingly. Further, this
Unit comes with a jumper (JP3) for adding the Auto Power Save option,
and switch contacts for setting the parity check On/Off function of
the SCSI bus. This settings will have to be done as needed according
to the operating conditions of the Unit.

Transportation and Precautions
When Transporting the Unit, exert extreme care so as to prevent it
from being subjected to excessive shock and vibration. It is
recommended to use the same packing box of the Unit for transporta-
tion or storage.

Avoid taking any action that would expose directly to the outside
air the disk enclosue in which the magnetic disk media and magnetic
heads are sealed.

Printed-Circuit Board Assembly
This assembly incorporates an SCSI interface circuit, buffer RAM,
data manager, read/write control circuit, servo-control circuit and
spindle motor drive circuit. It exerts control on the overall opera-
tion of the Unit and the Interface.

The Unit comes in frame having 10 mounting screw holes. This frame is
insulated from the disk enclosure assembly with shock absorber. In
configuring an integral system with the Unit, see to it that the disk
enclosure assembly will spearated from the system cabinet with a
clearance of at least 2.54 mm provided around the Unit.

 Power Disconnection
 When the power voltages of +5 VDC or +12 VDC has dropped below the
 specified value, this Unit interprets it as power outage. Upon power
 off, the Autoretract function of the Unit activates to automatically
 move the magnetic head to the Contact Start Stop (CSS) area.

Interface Specification
The Unit is provided with connector J1, used for connection to SCSI
bus, and connector J3 for power supply. The unit to be located at the
farthest end of the cable has to be fitted with terminating
resistors. When Initiator and Target differ from each other in power
source, it is recommended to supply power for terminaing resistance
from Pin 26 of SCSI bus.

                   Single Initiator/Single Target
        +----------------+                    +---------------+
        |   Initiator    +--------------------+    Target     |
        |                |                    |               |
        +----------------+                    +---------------+

                   Single Initiator/Multi Target
        +----------------+                    +---------------+
        |   Initiator    +-----------+--------+    Target     |
        |                |           |        |               |
        +----------------+           |        +---------------+
                                     |        +---------------+
                                     +--------+    Target     |
                                              |               |

                   Multi Initiator/Multi Target
        +----------------+                    +---------------+
        |   Initiator    +-------+---+--------+    Target     |
        |                |       |   |        |               |
        +----------------+       |   |        +---------------+
                                 |   |
        +----------------+       |   |        +---------------+
        |   Initiator    +-------+   +--------+    Target     |
        |                |                    |               |
        +----------------+                    +---------------+

Connector J1
A 50-pin nonshielded connector is use for interface with SCSI bus.
For SCSI bus, a 50-Conductor Flat cable or 25-Single Twisted Pair
cable can be used. For impedance matching, a cable of 100 ohms 10%
of impedance, with conductor diameter larger than 28 AWG is

Example of recommended connector on J1 cable side:

     Du Pont 66900-250 or equivalent (Integrated housing and pins).

Connector J3
The power supply connector J3 is AMP P/N350211-1 or equivalent.
The AMP P/N 1-480424-0 is applicable to a connector housing on the
cable side. In selecting a power cable, take into account the current
consumption of the Unit and the necessary length of the cable itself,
and use connector pins of material applicable to that of the

 | +--J3--------+ +-J1-   pin 1  +12 V DC
 | | 1  2  3  4 | | 1     pin 2  +12 V DC Return
 | +------------+ +--     pin 3   +5 V DC Return
 +------------------      pin 4   +5 V DC

Connectors J1 and J3 are molded as a unit.

Connector J8
This Unit is provided with a signal connector used to illuminate LED
to indicate that the Unit is busy in exchanging data/command to and
from the Initiator.

The signal connector is ELCO 00 8283 0211 00000 or equivalent.

 The ELCO 60 8283 3028 45000 is applicable to a housing on the cable
 side and ELCO 60 8283 0513 99 808 is a receptacle contact.
     |1   2|      1: LED, Anode
 ----+-----+PWB-  2: LED, Cathode

SCSI Interface Signals
The Unit employs a SCSI Single-Ended type interface.

The Single-Ended type interface uses a terminal resistance of 220 /
330 .

The logical specification and the electrical specification of the
signals dealt with in this section are as follows:

 1. Output Characteristics
    Signal assertion
    =0.0   0.4 VDC @ I=-48 mA
    Signal negation
    =2.5   5.25 VDC

 2. Input charateristics
    Signal true : "1"
    =0.0   0.8 VDC @ I=500  A
    Signal false : "0"
    =2.0   5.25 VDC
    (minimum input hysteresis = 0.2 VDC)

 3. Terminator power
    VTerm = 4.0  5.25 VDC @ I=800 mA


NEC D3856 THEORY OF OPERATION 806-521348-0 REV. 1, 1991

Outline and Features
The D3856 is a magnetic disk unit using 3.75" magnetic disk media and
mini-Winchester type magnetic heads with an unformatted storage
capacity of 131.3 Mbytes and adopts a SCSI interface (Small Computer
System Interface).

The rotary voice coil motor employed in the magnetic head drive
mechanism allows to realize write and read operations with high-speed
seek and high reliability, and its write system adopts the 1-7 RLL
modulation method.

The use of the Winchester technique has made it possible to
accommodate the magnetic disk media and magnetic head section in an
enclosed aluminium-alloy enclosure, which perfectly protects them
from outside dust for higher reliability.

The sector-servo method is adopted, in which servo signal are
obtained from the data recording surface for positioning the magnetic
head, and the type voice coil motor in use has allowed to attain a
high-speed seek in 19 ms of average seek time.

The magnetic disk medium comes with a CSS (Contact Start Stop) area
at the innermost circumference, which, coupled with an Auto Retract
and Auto Carriage Lock mechanisms, assures a high reliability against
vibration and shock during transportation.

The Unit adopts an interface conforming to the ANSI X3.131-1986 small
computer system interface, which is standard for small computer

The Unit supports SCSI CCS (Common Command Set), as well as various
option commands that are convenient for controlling the unit.

The Arbitration function and the Disconnect/Reconnect function
provided in the Unit serve to make an efficient use of the SCSI Bus.

An Asynchronous Single Ended interface is in use.

The Read Look Ahead Cache function is supported.

High speed processing is availabe, as it allows to use the magnetic
disk unit having 1.5 megabyte/sec. of read-write capabilities with
1:1 interleaving.

 Seek Time
       |                                  | D3856  |
       |Track-to-Track         msec. typ. |   8    |
       |Average                msec. typ. |  19    |
       |                       msec. max. |  37    |
       |Latency                msec. avg. |   8.68 |

Logical Connection with SCSI Initiator
This Unit, operating as the SCSI target, has no initiator function.
Logical connection of the Unit and the SCSI initiator is performed
in accordance with the SCSI logic specification. This Unit is
provided with the Arbitration function which can Disconnect/Reconnect
the logical connection with the SCSI initiator. If the initiator has
no Disconnect/Reconnect function by either sending the Identify (80H)
of SCSI message or sending Message Reject code in response to the
Disconnect request from this Unit.

The logical connection of SCSI starts with the Bus Free Phase which
is one of SCSI Bus Phases. The connection is terminated at the
Information Transfer Phase via the Selection Phase in the case of the
Non-arbitration system, and terminated at the Information Transfer
Phase via the Arbitration Phase and the Selection Phase in the case
of the Arbitration system.

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