
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


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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



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

 Jumper Setting
 ==============

 x = Jumper set at factory



 SW1  SCSI ID
 ------------
                                                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.


 NOTES
 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
 cable.



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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


 Installation
 ------------
 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.


 Frame
 -----
 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
 recommended.

 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
 conductors.

 +-----------------------
 | +--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



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                      F   E   A   T   U   R   E  S
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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.

 Features
 --------
 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
 systems.

 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.


