20 MB Hard Drive  (250-4062)          Settings         Faxback Doc. # 4969

* The 20 MB Hard Disk Drive is a half-height Winchester fixed-disk drive.

* The 20 MB Hard Disk Drive interface is compatible with the Seagate
  ST506/ST412 standard interface.

* Can operate at temperatures from 50 to 113`F with 8 to 80% non-condensing
  humidity.

* The standard Drive Select setting set at the factory configures the 20 MB
  Hard Disk Drive as the first (primary) disk drive.  The standard
  Terminator setting configures the Hard Disk Drive as the terminal disk
  drive.  Possible pin settings for the 20 MB Hard Disk Drive are shown in
  the following chart.

SEAGATE MODEL ST-225

This disk drive has eight pairs of pins.  The first four sets of pins are
for Drive Select.  Jumper one of these pairs to configure the hard disk as
Drive 1,2,3 or 4 (C,D,E or F), respectively.

NOTE: The third and fourth sets of pins provide hardware support for a
third and fourth hard disk.  The Hard Disk Controller board (25-4060) for
your computer does not support more than two hard disk drives.

The last four pairs of pins are not used.

This drive includes a Terminator Resistor on the bottom of the unit for
drive termination.  Be sure the resistor is installed to configure the hard
disk as the terminal drive.  Remove the resistor to use the 20 MB Hard Disk
as a non-terminal drive.

Setting up the MR522 Drive:

Check the settings on the dip switches near the back edge of the PCB on the
bottom of the disk drive (see Figure 1) to be sure they are set as shown.

│                        PCB                                        │
│                          ┌──────┐┌──────┐                         │
│                       SW1└┬┬┬┬┬┬┘└┬┬┬┬┬┬┘SW2                      │
│                                                                   │
└─┐        ┌┐ ┌────────────┐││││││  ││││││  ┌┐ ┌──────┐             │
  │        ││ │            │││││││  ││││││  ││ │      │             │
  └────────┘└─┘            └┼┼┼┼┼┼──┼┼┼┼┼┼──┘└─┘      └─────────────┘
          RADIAL       (R) ─┘│││││  │││││└─ TERMINATION SWITCH
          DIAGNOSTIC   (D) ──┘││││  ││││└── NOT USED
      DRIVE SELECT 4 (DS4) ───┘│││  │││└─── TERMINATION SWITCH
      DRIVE SELECT 3 (DS3) ────┘││  ││└──── TERMINATION SWITCH
      DRIVE SELECT 2 (DS2) ─────┘│  │└───── TERMINATION SWITCH
      DRIVE SELECT 1 (DS1) ──────┘  └────── TERMINATION SWITCH

             SW1 (Switch Block 1)       SW2 (Switch Block 2)
            1   2   3   4   5   6      1   2   3   4   5   6

FIRST       On Off Off Off Off  On     On  On  On  On  On  On
INTERNAL HD 

SECOND      On Off Off Off  On Off    Off Off Off Off Off Off
INTERNAL HD 

SETTING UP THE ST225 DRIVE

Check the position of the jumper on the back edge of the PCB on the bottom
of the hard disk drive (see Figure 2) to be sure the jumper is set to the
desired position.
┌────────────────────────────────────┬──────────────┐
│                                  O │              │
│                                 /  │              │
│                               /    │              │
│                              /     │              │
│                             /      └──────────────┤
│                            /                      │
│           _ OPTIONAL GROUNDING POINTS _           │
│         /                               \         │
│       /                                   \       │
│      /                                     \      │
│     /                     Resistor          \     │
│    /                   Termination ╓──╖       O   │
│   /                           Pack ║  ║           │
│ O                                  ║  ║           │
│                                    ╙──╜           │
│    J3        J1          J7 16-Pin       J2       │
│  ┌┐││┌┐│││││││││││││││││┌─┬┬┬┬┬┬┬┬─┐││┌┐│││││││││││
└──┘└┴┴┘└┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┴┘ ││││││││ └┴┴┘└┴┴┴┴┴┴┴┴┴┴┘
   4-Pin    34-Pin                       20-Pin

                                                  ┌──┐
FIRST        1    3    5    6     9    11    13   │15│  Terminal Resistor
INTERNAL HD  2    4    6    8    10    12    14   │16│  Installed
                                            ┌──┐  └──┘
SECOND       1    3    5    6     9    11   │13│   15   Terminal Resistor
INTERNAL HD  2    4    6    8    10    12   │14│   16   Removed
             │    │    │    │     │     │   └─┼┘    │
                  │
        Radial      Write  Life  DS4   DS3   DS2   DS1               
            Recovery Test  Test            
              Mode

When installing a Seagate drive as the second hard disk drive the
termination resistor should be removed from the drive prior to
installation.

(css/BKL-01/10/96)