Flash Memory; Sensors; Read-After-Write - Seagate STD2401LW-S Product Manual

Theory of operations

Flash memory

Sensors

Read-After-Write

Because the Scorpion 40 uses flash memory, the drive firmware can be easily
upgraded when new revisions of the firmware are released. The flash memory is 1
Mbyte in size.
You can load new firmware in one of three ways:
Using a specially encoded firmware upgrade cartridge
Issuing a SCSI Write Data Buffer command to download the firmware to the
EEPROM
Through the drive serial port
Refer to Chapter 4 for information about loading new firmware using a Seagate
firmware upgrade cartridge.
A number of mechanical and optical sensors are integrated in the drive design. The
cartridge in and cartridge loading sensors are mechanical sensors that determine the
position of the loading mechanism. The other mechanical sensors report specific
information based on detecting the open or closed state of four recognition holes in
the DAT cartridge. The open or closed state of these holes designate tape type,
whether the tape is a cleaning cartridge, whether the tape is prerecorded and
whether the tape cartridge is write-protected. These mechanical sensors and the
sensor for the cartridge in status comply with the DDS-4 standard requirements for
the cartridge.
The beginning-of-tape (BOT) sensor is an optical sensor that uses the light path
transmissivity of leader tape, as specified in the DDS cartridge standards. The
sensor is also designed to recognize media recognition system (MRS) cartridges,
which have a series of alternate opaque and clear stripes at the beginning of the
tape.
The reel sensors for the two reels are optical. Optical sensors also detect the
mechanism position during mode changes.
The capstan sensor is a magnetoresistive Hall sensor that detects a magnetic field.
The cylinder sensors are coil and magnet sensors. Each reel motor contains a high-
resolution, optical speed encoder.
The read-after-write (RAW) technique provides a means of verifying that host data
was written on the tape correctly by applying a read check immediately after writing
the data to tape. The read check is a comparison of the actual signal quality versus a
predetermined acceptable threshold level.
If a frame is identified as bad, it is rewritten later down the tape. The bad frame is not
necessarily rewritten immediately. It can be rewritten after three, four or five other
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