
M 8 4 2 5 S    MINISCRIBE
NO MORE PRODUCED                                      Native|  Translation
                                                      ------+-----+-----+-----
Form                 3.5"/HH               Cylinders     612|     |     |
Capacity form/unform    21/   25 MB        Heads           4|     |     |
Seek time   / track  68.0/15.0 ms          Sector/track   17|     |     |
Controller           SCSI1 SINGLE-ENDED    Precompensation
Cache/Buffer             1 KB DUAL-PORTED  Landing Zone
Data transfer rate    1.000 MB/S int       Bytes/Sector      512
                            MB/S ext
Recording method     RLL 2/7                        operating  | non-operating
                                                  -------------+--------------
Supply voltage     5/12 V       Temperature *C         4 50    |    -40 57
Power: sleep              W     Humidity     %         8 80    |
       standby            W     Altitude    km    -0.061  3.048|
       idle          13.0 W     Shock        g         8       |     50
       seek               W     Rotation   RPM      3600
       read/write         W     Acoustic   dBA        50
       spin-up            W     ECC        Bit   32
                                MTBF         h      20000
                                Warranty Month
Lift/Lock/Park     YES          Certificates     CSA,FCC,UL1950               

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                        L   A   Y   O   U   T
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MINISC.  8425S  PRODUCT MANUAL P/N 1052 REV. B, JULY 24, 1987

  +---------------------------------------------------------+
  |                                                     F1xx|Fuse
  |                                              +------1 ++|XX
  |                                              +------+ |||XX
  |                                              Drive    |||XX
  |                                              Select RP3+|XX
  |                                                       ++|XX J1
  |                                                       |||XX
  |                                                       |||XX
 ++                                                     RP2+|XX
 ++                                                       ++|XX
  |                                                       |||XX
  |                                                       |||XX
  |                                                     RP1+|XX
  |                                                         |XX
  |                                                         |  1
  |                                                         |
  +---------------------------------------------------------+
                                                     XXXXXX J3
                                                     Power



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                      J   U   M   P   E   R   S
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MINISC.  8425S  PRODUCT MANUAL P/N 1052 REV. B, JULY 24, 1987

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

 Drive Select
 ------------

    +-----------+
    |o o o o o 1|
    |o o o o o o|
    +-----------+
     | | | | | +- SEL 0
     | | | | +--- SEL 1
     | | | +----- SEL 2
     | | +------- D (Disable Parity)
     | +--------- E (Low Powered)
     +----------- F (Diagnostics)

 Addressing
 ----------
 Communication on the SCSI bus is allowd between only two (2) SCSI
 devices at any given time. There is a maximum of eight (8) SCSI
 devices. Each SCSI device has an SCSI ID bit assigned.

 When two (2) SCSI devices communicate on the SCSI bus, one acts as an
 Initiator and the other acts as a Target. The Initiator originates
 an operation and the Target performs the operation.

 An Initiator may address up to eight (8) Logical Units (LUN) attached
 to one Target. The M8-SCSI has only one Logical Unit Attached (LUN =
 0).

 Address selection on the M8-SCSI is accomplished by the use of three
 jumpers:

          | 0 1 2 3 4 5 6
    ------+--------------
    SEL 0 | 0 1 0 1 0 1 0
    SEL 1 | 0 0 1 1 0 0 1
    SEL 2 | 0 0 0 0 1 1 1

 When left OPEN, the corresponding bit is a ZERO (0).


 Mode Jumpers
 ------------
 Three additional jumpers are supplied on the M8-SCSI Printed Circuit
 Board (PCB) with the following functions when SHORTED:

 Jumper D Disable Parity
 Jumper E Low Power/Auto Park Mode
 Jumper F Invokes Offline Diagnostics following reset, which consists
          of infinite seek tests (random or oscillating).



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MINISC.  8425S  PRODUCT MANUAL P/N 1052 REV. B, JULY 24, 1987

 Notes on Installation
 =====================

 Recommended Mounting Configuration
 ----------------------------------
 The MiniScribe 8425 SCSI quarter size drive is designed to be used in
 applications where the unit may experience shock and vibrations at
 greater levels than larger and heavier disk drives.

 Two features which allow greater shock tolerances are the use of
 rugged media and shock mounts. To take full advantage of the shock
 mounts, however, it is necessary to provide a 0.1 inch clearance on
 both the top and bottom of the drive. This clearance allows for move-
 ment of the drive during acceleration.
 The drive may be mounted in any attitude.

 The drive is mounted using 6-32 screws, 1/8 inch maximum penetration.
 The customer should allow adequate ventilation to the drive to insure
 reliable drive operation over the operating temperature range.


 Mechanically Isolated Mounting Points
 -------------------------------------
 Four side mounting and four base mounting points are provided to the
 customer. Each mounting point is mechanically isolated from the
 head/disk assembly.


 Magnetic Field
 --------------
 The externally induced magnetic flux density may not exceed 3 Gauss
 as measured at the disk surface.


 Read/Write Electronics
 ----------------------
 One integrated circuit is mounted within the sealed enclosure in
 close proximity to the read/write heads. Its function is to provide
 one (1) of four (4) head selection, read preamplification and write
 drive circuitry.


 Drive Mechanism
 ---------------
 A brushless DC direct drive motor rotates the spindle at 3600 rpm.
 The motor/spindle assembly is dynamically balanced to provide minimal
 mechanical runout to the disks. A dynamic brake is used to provide a
 fast stop to the spindle motor when power is removed.


 Air Filtration System
 ---------------------
 Within the sealed enclosure, a 0.3 micron filter coupled with a
 breather filter provides over the drive life a clean, above
 atmospheric pressure environment to the heads and disks.


 Head Positioning Mechanism
 --------------------------
 Four read/write heads are supported by a carriage mechaism coupled to
 the stepper motor through a rack-and-pinion motion translator.


 Read/Write Heads and Disks
 --------------------------
 Data is recoreded on two (2) 95 mm diameter disks through four (4)
 low force, low mass Mini-Winchester type ferrite heads.


 Caution/Warning
 ---------------
 The Miniscribe drive is a precision product weighing 1.8 pounds.
 During handling the unit must not be dropped, jarred or bumped.
 Otherwise, damage to the heads and disks may occur. When the drive is
 removed from the Miniscribe shipping container and not immediately
 secured within a chassis through its shock mounts, it must be stored
 on a soft padded surface.

 Failure to comply with the above procedure will render null and void
 all warranties.


 Electrical Interface
 --------------------
 The Small Computer System Interface (SCSI) on the M8-SCSI uses single
 ended drivers and receivers, which allow a maximum cable length of 20
 feet (6 meters) from the first to the last device (up to 8 devices)
 on the bus.

 All assigned signals are terminated with 220 ohms to +5 volts and 330
 ohms to ground at each end of the cable. All three (3) terminator
 networks on the M8-SCSI are removable.

 All signals driven by the M8-SCSI are Open Collector and have the
 following output characteristics:

    Signal Assertion        0.0 VC to 0.4 VDC
    Max. Driver Output      48 mA (sinking) @ 0.5 VDC
    Signal Negation         2.5 to 5.25 VDC

 All signals received by the M8-SCSI shall have the following input
 characteristics:

    Signal True             0.0 VDC to 0.8 VDC
    Max. Total Input Load   -0.4 mA @ 0.4 VDC
    Signal False            2.0 to 5.25 VDC
    Min. Input Hysteresis   0.2 VDC


 J1 SCSI Connector
 -----------------
 A 50 pin flat ribbon connector is provided at J1. The 3M P/N 3425-
 3000 cable connector is recommended.

 Pin 26 Term Power
 Termpower is +5 volts thru a 1 amp microfuse. Loss of this fuse will
 result in the disk drive appearing dead. Reversal of the connector
 with pin 25 grounded will cause this fuse to blow.


 J3 Power Connector
 ------------------
 Power is applied through J3, a 4 pin AMP connector. The recommended
 mating connector is AMP P/N 1-480424-0 utilizing pins AMP P/N
 350078-4.

  +-----J3-----+   pin 1    +12 VDC
  | 4  3  2  1 |   pin 2    +12 Volts Return
  +------------+   pin 3    + 5 Volts Return
                   pin 4    + 5 VDC


 Cable Connection
 ----------------

 Single Host, Single Drive
 +-------+                    +-------+
 | HOST  +----SCSI-Bus--------+  M8-S |
 |      X+--------------------+      X|
 +-------+                    +-------+


 Single Host, Multiple Drives
 +-------+                    +-------+
 | HOST  +----SCSI-Bus--------+ M8-S  |
 |      X+------+  +----------+       |
 +-------+      |  |          +-------+
                |  |          +-------+
                |  +----------+ M8-S  |
                |  +----------+       |
                |  |          +-------+
                |  |          +-------+
                |  +----------+ M8-S  |
                +-------------+      X|
                              +-------+


 Multiple Host, Multiple Drives
 +-------+                    +-------+
 | HOST  +----SCSI-Bus--------+ M8-S  |
 |      X+------+  +----------+       |
 +-------+      |  |          +-------+
                |  |          +-------+
                |  +----------+ M8-S  |
                |  +----------+       |
                |  |          +-------+
 +-------+      |  |          +-------+
 | HOST  +------+  +----------+ M8-S  |
 |      X+--------------------+       |
 +-------+                    +-------+

 X = Terminator Installed



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                      F   E   A   T   U   R   E  S
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MINISC.  8425S  PRODUCT MANUAL P/N 1052 REV. B, JULY 24, 1987

 Introduction
 ------------
 The MiniScribe M8-SCSI (Small Computer System Interface - ANSI
 X3.131-1986) series of 3 1/2 inch disk drives are half height random
 access storage devices of 21 Megabytes of formatted data (25 MB un-
 formatted) containing 2 plated disks and utilizing Winchester style
 flexure technology.

 High performance and high unit reliability are achieved by the
 utilization of a proven microprocessor spin control and rack-and-
 pinion stepper mechanism. The heads, disks and actuator assemblies
 are within a sealed enclosure containing recirculating and breather
 filters to supply clean air and equalized pressure to the head and
 disk environment. Quality mechanical construction with a sophistica-
 ted single printed circuit board allows for maintenance-free
 operation throughout the life of the drive.

 The M8-SCSI series disk drive uses the industry standard Small
 Computer System Interface (SCSI) compatible interface capable of up
 to 1 Megabyte/second (8 megabits/second) data transfer rate. The
 drive also features power up, user invoked or offline diagnostics and
 has full support of disconnection. Defect handling is entirely
 transparent to the host system as well as seek retry and error
 correction.

 The unit size and shock mounting are identical to the industry
 standard half height 3 1/2 mini floppy mounting dimensions and it
 uses the same power connector.


 Track Zero Detector
 -------------------
 The Track Zero Detector resides on the stepper motor. This optical
 sensor consists of a light source and a receiver which when blocked
 by an interrupter on the motor shaft indicates one of several logical
 Track Zero positions. The microprocessor determines the physical
 location of Track Zero from the redundant logical Track Zeros.


 Seek Time
 ---------
       +----------------------------------+--------+
       |                                  | 8425S  |
       +----------------------------------+--------+
       |Track-to-Track         msec. typ. |  15    |
       +----------------------------------+--------+
       |Average                msec. typ. |  68    |
       |                       msec. max. | 150    |
       +----------------------------------+--------+
       |Latency                msec. avg. |   8.33 |
       +----------------------------------+--------+


 Media Defect Criteria
 ---------------------
 All defects are preassigned from the factory.


 Host Interface and Data Buffer
 ------------------------------
 The host interface and data buffer are integrated in one single
 semicustom circuit with the following features:

 ANSI X3.131-1986 compatible (SCSI) Host interface operating in Target
 mode only.

 Capable of Arbitration and disconnection.

 Parity generation and checking (user selectable).

 Dual ported 1024 bytes buffer, eliminates the need for sector inter-
 leaving (1 to 1).


 Defect Management
 -----------------
 There is one (1) alternate block allocated for each cylinder for a
 total of 612 allocated alternate blocks. This assures adequate
 coverage defective blocks and decreases the time necessary to react
 to alternate blocks.



 Diagnostic and Exercise Routines
 --------------------------------
 The microprocessor performs wake up diagnostics upon application of
 power. If an error is detected, the processor will flash a warning by
 blinking the activity LED. Some errors are fatal in that they do not
 return to the program until power is cycled.

 If no errors are detected, the processor tests Jumper E to determine
 its state (open or closed). Briefly, Jumper E (Drive Exercise
 Options) is as follows:

 Power-up sequence of events is as follows:

 1. Apply power

 2. The microprocessor runs power on diagnostics and then allows motor
    spin up.

 3. Test Jumper E. If open, go to normal operation. If closed,
    continue to Step 4.

 4. Display code level (5 bits), e.g. 00001

 5. Recalibrate access, then seek to maximum cylinder.

 6. At this point the sequential seek burn-in will begin.

 Error codes may be generated by the microprocessor to indicate hard-
 ware failures or warnings that are detected during power-on
 diagnostics, burn-in mode, or normal operation. Error codes are
 diaplayed in a "morse-code" type manner. Bits may be interpreted
 and converted into hexadecimal error codes. "Zeros" are indicated by
 a short (1/2 second) flashingn mode. "Ones" are indicated by a short
 (1/2 second) continuous ON mode. Error "Words" are separated by a one
 second LED off time.

    Zero                  = 0.5 second flashing mode
    One                   = 0.5 second continuous ON mode
    Between Bits          = 0.3 second Off
    Between Repeat Cycles = 1.0 second Off

 Listed Below are the binary to hexadecimal conversion values:

  0 = 0000   4 = 0100   8 = 1000   C = 1100
  1 = 0001   5 = 0101   9 = 1001   D = 1101
  2 = 0010   6 = 0110   A = 1010   E = 1110
  3 = 0011   7 = 0111   B = 1011   F = 1111


 Message Definitions
 -------------------
 Code 0 - Microprocessor RAM error
 Code 1 - Microprocessor ROM checksum error
 Code 2 - Interface chip diagnostic failure
 Code 3 - Write Fault latch will not reset
 Code 4 - Index pulse not detected during spinup
 Code 5 - Unable to reach 3600 rpm in 600 revs.
 Code 6 - Unable to stabilize spin speed in 10 seconds
 Code 7 - Unable to maintain spin speed to 0.5%
 Code 8 - Unable to uncover Track Zero sensor
 Code 9 - Unable to cover Track Zero sensor
 Code A - Track Zero interrupter misadjusted
 Code B - Shipping zone error, crash stop misadjusted
 Code C - Carriage stuck during recal error
 Code D - Seek errror during burn-in or recal
 Code E - No hall transitions during spin-up
 Code F - Unexpected interrupt from processor


