Seagate STT8000A manual Control circuits, Head design, Sensors and switches

Theory of operations Chapter 7

Control circuits

The control logic module shown in Figure 7-1 includes a buffer manager to handle data movement between the 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 a specially written tape cartridge.

The 512-KB DRAM data buffer allows the drive to maintain streaming when the host cannot provide data continuously at the tape streaming rate.

The write driver receives data from the write formatter and generates write current, causing data to be written on tape by the tape head.

The read channel amplifies and conditions the signal from the tape head and passes it back to the read formatter.

The head stepper and drive motor both receive current from the control logic to control the stepping of the head from track to track and to move the tape forward and back across the tape head.

Head design

The recording/playback head is a state-of-the art, thin-film design—a thin-film inductive write head paired with an advanced magneto-resistive read head. This head design provides the drive with exceptional performance and reliability. The material composition of the head also results in exceptional wear characteristics, resulting in stable performance throughout the life of the drive.

Flash EEPROM

Because the drive uses flash EEPROM (electronically erasable, programmable read-only memory), the drive firmware can be easily upgraded when new revisions of the firmware are released. The circuitry includes 128 KB of flash EEPROM.

You can load new firmware by using a specially encoded firmware upgrade cartridge.

Refer to chapter 4 for information about loading new firmware using a Seagate firmware upgrade cartridge.

Sensors and switches

A number of mechanical and optical sensors and switches are integrated in the drive design. The Cartridge In switch detects when a cartridge is fully loaded and positioned against the A-plane datum of the cartridge. The Unsafe switch senses

STT8000A Product Manual Page 71