Seagate STT20000N, Руководство по эксплуатации продукта

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Theory of operations Chapter 7
STT20000N Product Manual Page 53
Mechanics
The mechanical package for the STT20000 SCSI minicartridge drive was designed
to provide all the advantages of easy cartridge loading and unloading while
maintaining the positioning accuracy necessary for high-density data recording. The
orientation of the cartridge is the same as the majority of QIC minicartridge drives in
the field.
Cartridge load mechanism
The cartridge is inserted in the drive by sliding it through the aperture in the bezel
and into a tray mechanism. When fully inserted the back portion of the cartridge
protrudes about 3/4-inch from the aperture. A switch is actuated at this point that
causes a microprocessor to complete the loading operation.
When the tape is in motion, the amber LED on the front panel flashes. The LED is
not lit when the tape is positioned at BOT.
Capstan drive motor assembly
In the STT20000 SCSI minicartridge drive, the cartridge is driven by the capstan/belt
motor assembly, which is on a linear slide. The cartridge is loaded against the
cartridge drive roller which exerts a net radial dynamic force of 18 to 26 ounces. The
motor is a brushless DC drive motor with integral capstan which is designed to
provide maximum reliability.
The motor operates from the 12V nominal supply and moves the tape at speeds
from 35 to 100 inches per second (IPS).
Chassis
The drive mechanism is mounted in a molded frame that provides the mounting
holes for the industry standard 3.5-inch by one inch form factor. A 5.25-inch
mounting kit is an available option. The bezel is a simple snap-on design that is
available in several standard and custom colors. The front-panel LED is amber and
indicates tape activity.
Control circuits
The control logic module shown in Figure 7-1 includes a buffer manager to handle
data movement between the SCSI controller, the buffer, and the tape formatter. This
module also includes logic to perform ECC and CRC generation and testing,
WRITE/READ data formatting, head stepper control, and drive motor control.
The microprocessor directs all functions performed by the control logic. The
instructions are read from a flash EEPROM, which can be updated with new
firmware through either the SCSI interface or a specially written tape cartridge.