User's Manual

Scorpion 240 Product Manual

The DDS-4 drive mechanism

The Scorpion 240 uses the helical scan recording method with a four-head cylinder

design. Four direct-drive motors and one brush-type motor are used in the drive. The

read and write functions use LSIs. Engineering decisions—such as the modular

partitioning of the electronics and use of surface mount, low power commercial and

custom LSIs—allow the drives to conform to the industry-accepted 5.25-inch, full-

height form-factor. These design features are also important contributors to the

overall reliability, durability and performance of the drive.

The Scorpion 240 mechanism is designed for minimum tape wear and prevention of

damage to the tape. The modes or operational states, such as stop, rewind and play,

reduce mechanism and tape wear. Fewer mechanical mode changes result in less

wear on key drive components. In some cases, the need for a mode change is

circumvented using the Pause mode, which stops the tape without activating the

mechanism. All mode selection is performed by the controller firmware. The host

computer does not directly control mode selection.

A custom timing tracking design, combined with the four-head cylinder design,

implements the specifics of the DDS-4 recording format standard and provides the

precision required to perform seamless appends, or the ability to add subsequent

recorded data frames immediately adjacent to the last data frames written on the

tape.

A bank of jumpers is available at the rear of the drive. These jumpers allow you to

set the SCSI ID for the drive and to change configuration choices. Refer to chapter 3

for information about setting these jumpers.

By using the jumpers, you can also enable terminator power if needed. (The default

for internal models is with terminator power disabled. For external drives, the default

is with terminator power enabled.)

Note.

The Scorpion 240 comes supplied with a terminator power fuse to provide

protection from component damage in case the SCSI cable is connected

incorrectly.

Two rectangular front-panel light-emitting diodes (LEDs) indicate a drive busy status

and tape cartridge in place status. When blinking, these LEDs also function as fault

indicators. (Refer to Chapter 4 for a summary of the function of these LEDs.) The

external subsystem also provides an additional LED on the front panel to indicate

cleaning status.

Helical scan recording—four-head design

In helical scan recording, the heads are positioned opposite one another on a

cylinder, which is tilted approximately 6 degrees from the vertical plane and rotates

counterclockwise at 10,000 revolutions per minute (rpm). At the same time, the tape

moves slowly (20.375 mm per second in DDS-4 mode) in a horizontal path around

part of the cylinder. This simultaneous motion of cylinder and tape results in the head

traveling across the width of the tape in a helix-shaped motion.

The cylinder is designed with four, long-life heads—two read and two write heads.

These heads are set opposite one another with a rotation sequence of: write A, read

B, write B, read A (or write A new, read B old, write B new, read A old). The