High-performance adaptive-speed/CAV CD-ROM drive

Abstract

Abstract-This paper describes a novel type of CD-ROM drive which can automatically distinguish between two basic operating modes: continuous playback and continuous access. The drive, based on the adaptive-speed technology, is optimized for a very high data throughput during sustained read-out using a new cubic overspeed profile. In addition, by detecting the state of continuous access and switching the spindle motor into a CAV (constant angular velocity) loop, the drive features very low power consumption. Two dedicated firmware algorithms which can detect one of the two operating modes either at the bit-engine level or at the data-path level are also presented. While implementing the algorithm at the data-path level, the paper will also approach a novel technique for the optimization of the data flow via controlling the speed of the spindle motor. A better buffer management can therefore be achieved. Last but not least, the cubic overspeed profile is shown to be optimal not only for sustained playback but also while the drive is performing either a unique seek action or a short sequence of seeks.

Adaptive-speed/CAV algorithm in a CD-ROM drive to accomplish high data transfer rate and low power consumption

“…The profile is optimized [3] such that the maximum overspeed N,,, > iYout which can be handled by the system is never exceeded at the end of a random outward-oriented third-stroke seek. The braking possibilities of the spindle motor are also taken into account.…”

“…The adaptive-speed profile should be optimized such that a maximum of the average bit rate is obtained while reading out data from the inside to the outside of the disc. An example of such optimization which leads to a cubic overspeed3 profile is presented in [3]. Further, the adaptive-speed profile can also be refined for a short sequence of data seeks when the CAV control does not need being switched on.…”

<title>Adaptive-speed quasi-CAV algorithm in a CD-RW drive</title>

“…LBA <T 1 nno V ismth e algorithm and conceptual zoning of the recording areas. V, is the disc recording speed for zone n. where To is the subcode location of the logic block address (LBA) where the data recording area starts on a disc, R0 is the physical radius of To, Ti is the subcode location where the recording speed switches from Vi to Vi+,, n is the number of speed zones, Ri is the physical radius of Ti, Vi is the recording velocity of speed zone i where the subcode time starts at Ti_!…”

The CD-ROM Drive

“…Modern drives use either constant angular velocity (CAV) or a predefined speed profile [103] between CLV and CAV. Concepts that combine two or even all of these three driving strategies are also known [105]. This turntable motor control will be discussed throughout Section 4.8.…”

“…In case of current-controlled motors, the above relation needs being modified accordingly [105]. system tolerances.…”