HP Surestore 160ex - Optical Jukebox, Руководство по обслуживанию

Страница: 214 / 230

Theory of Operation
Optical Drive Mechanism
Chapter 6 6-22
decodes the various commands and messages on the SCSI bus and
instructs the drive to take appropriate action.
The encode/decode function encodes and decodes data for read and write
transfers. During a write function, user data is sent via the SCSI bus.
The encoder converts the parallel data into an encoded serial bit stream
that includes all the format and error correction features required to
meet the ANSI and ISO specifications. During reads, the decoder
converts the serial data stream, which includes format and error
correction features, into parallel data.
Central Processing Unit (CPU)
The central processing unit for all drive functions includes the loading
motor.
Gate Array
This component contains circuitry to interconnect the major blocks (CPU,
DSP, write/read channel).
DSP (Digital Signal Processor)
The DSP controls the following servos: spindle motor/speed, laser power
control, track following, seek/position maintenance, focus actuation, fine
position actuation, and coarse position actuation. Whenever the drive is
performing a read or write operation, all these servos are activated.
Read / Write Channel Electronics
Read/write channel electronics take analog data from the optical head
and convert it into digital "transitions." These transitions are decoded by
the encoder/decoder electronics in the controller chip to extract data from
format and error correction features. The write channel electronics take
the serial data stream from the encoder/decoder and convert the digital
pulses into analog data. This analog data is then sent to the optical
head.
Loading Motor
The loading motor loads and unloads the optical disk cartridge. The
loader motor includes a gear train and rack-and-pinion system that allow