344 MB SCSI Hard Drive  (250-4163)    Settings         Faxback Doc. # 5129

TECHNICAL INFORMATION

The Full Height and Half Height Rigid Disk Drives have many features in
common. The following comments apply to both drives.

* The drive is compatible with the industry standard (ANSI) SCSI host
  interface.

* The drive features an automatic actuator locking device to protect the
  mechanism during shipping and handling. The lock automatically disengages  
  when power is applied to the drive and engages when power is removed.

NOTE: Do not move the drive for 20 seconds after power is removed to make 
sure the actuator is locked.

DRIVE SELECT JUMPERS

The drive can be configured to have any Logical Address from 0 thru 7 on the
SCSI Bus. The standard Drive Select setting preset at the factory is IK 0
(Primary drive configuration.)

MOTOR START OPTION

A jumper installed enables the Motor Start Option. In this mode the drive 
will wait for a Start Unit Command from the host before starting the motor. 
With  the jumper removed the motor will start immediately when power is 
applied to  the drive. The drive is supplied from the factory with the 
jumper not installed.

PARITY CHECK

A jumper installed in the positions shown in figures on following pages 
enables a parity check of data on the SCSI Bus. With the jumper removed no 
parity check is performed. The drive is supplied from the factory with the 
jumper installed.

The following comments apply to the 344 MEG Full Height Rigid Disk Drive:

TERMINATOR POWER SOURCE SELECT

If the drive is to be configured as the Primary Drive the terminator resistor 
packs must be installed and a terminator power source selected. The TP jumper 
must be installed in one of two positions. With the jumper installed in the
horizontal position terminator power is supplied through the 
interface cable. With the jumper installed in the vertical position, 
terminator power is supplied by the drive. the drive is supplied from the 
factory with the jumper installed in the vertical position.

If the drive is to be configured as the Secondary Drive the termination 
resistor packs must be removed from the drive, in which case the TP jumper 
need not be installed.

GROUND SELECT

The Rigid Disk Drive is supplied with AC and DC grounds tied together and 
connected to the chassis ground. The installer may modify this ground 
arrangement to comply with different requirements. Either ground system may be 
isolated by removing the appropriate jumper. The drive is supplied from the 
factory with both jumpers installed.

THE FOLLOWING COMMENTS APPLY TO THE 170 MEG HALF HEIGHT RIGID DISK DRIVE:

TEST SEEK

With a jumper installed in this position the drive will perform continuous 
Seeks to random cylinders. The drive is supplied from the factory with this 
jumper not installed.

TERMINATOR POWER SOURCE SELECT

If the drive is to be configured as the Primary Drive the terminator resistor 
packs must be installed and a terminator power source selected. Jumpers may be 
installed in any of three positions.

With a jumper installed in position "A" the internal terminator power is 
supplied from the Rigid Disk Drive power connector.

With a jumper installed in position "B" the internal terminator power is 
supplied through the interface cable (Pin 26).

With a jumper installed in position "C" the drive will supply terminator 
power to Pin 26 of the interface cable. (In this case a jumper must be 
installed in position "A" also to supply power to the internal terminators.)

If the drive is to be configured as a Secondary Drive the terminator resistor 
packs must be removed and internal terminator power need not be supplied.

GROUND SELECT

The Half Height Rigid Disk Drive is shipped with the DC/HDA logic ground and
chassis ground joined together. These two grounds planes may be separated by 
repositioning the "U" shaped grounding washer on the motor control PWA as 
shown on page 27 of your harddrive manual.

NOTE: To separate the grounds, loosen the screw "A" and re-orient the washer 
so that it does not contact the ground run the screw at any point.

Hold the washer in place and re-tighten the screw.

(abo-07/29/93)