WO2005045832A1

WO2005045832A1 - A low power data storage system and a method thereof

Info

Publication number: WO2005045832A1
Application number: PCT/KR2004/002844
Authority: WO
Inventors: You Jip Won
Original assignee: You Jip Won
Priority date: 2003-11-05
Filing date: 2004-11-05
Publication date: 2005-05-19
Also published as: KR20050043098A

Abstract

The present invention is directed to a low power data storage system and method that determines the size of data written in a predetermined storage medium to have a predetermined value and controls the storage medium to be transited to an initial state after finishing writing the determined data, thereby excluding an idle mode and minimizing power consumed in storing data.

Description

A LOW POWER DATA STORAGE SYSTEM AND A METHOD THEREOF

Field of the Invention

The present invention relates to a low power data storage system and method and, more particularly, to a low power data storage system and method that determines the size of data written in a predetermined storage medium to have a predetermined value and controls the storage media to be transited to an initial state after finishing writing the determined data, thereby excluding an idle mode and minimizing power consumed in storing data.

Background Art

With the advent of various mobile terminals, it becomes more important to strictly manage the energy consumption of a mobile terminal in the aspect that it is possible to adopt mobile terminal functions through effective use of restrictive power. For effective energy consumption management, a mobile terminal adopts a hardware that has a power saving feature and a software that minimizes power consumption on the basis of data queuing. In particular, in a data transmitting function or a data reading function that constitutes dominant fraction of energy consumption of mobile device, continuous improvements in a relevant technology have improved the energy consumption, for example, via a disc drive scheduling.

On the other hand, in a data storing function that consumes relatively much power, any particular solution for reducing power consumption has not yet been suggested. The prior art simply reduces power that is supplied to a storage medium by controlling power supply along with completion of a data storing process. For example, it has been recently suggested a method for controlling power supply, wherein the method switches a storage medium to a stand-by mode automatically if a data storage or retrieval request is not generated for a predetermined time, and controls the storage medium to operate in the stand-by mode from a finish mode if an idle mode is continued for a predetermined time. However, when the storage medium operates in the stand-by mode, it is required to control the storage medium to operate in a start-up mode in order to write predetermined data. In case of a hard disc, a spinning up of a platter, a head focusing and a head tracking are performed simultaneously with the operation of the start-up mode, which might deteriorate a storage process. Furthermore, when the storage medium operates in an idle mode, it is required to continuously maintain the storage medium in the stand-by mode because it cannot be determined when generated data are input into the storage medium. Therefore, under the environment of not stringent energy supply, e.g., under an ordinary desktop computer or server environment, energy which is normally electricity is continuously supplied to the storage medium to store input data. This type of device management increases energy consumption. Furthermore, the aforementioned power supply control method, which controls operation modes of the storage medium by measuring the continuation time of an idle mode, is not so much effective if the period of generating input data is short. Therefore, there is a strong desire for invention of a energy efficient storage system and method capable for excluding an idle mode of a storage medium and preventing unnecessary energy consumption by precisely estimating the triggering point of a data storage command and the starting/terminating point of a write mode of the storage medium on the basis of the size of data written, recording rate and manufacturing characteristics of the storage medium, and then controlling the operation of the storage medium on the basis of the estimated information..

Brief Description of the Drawings

FIG 1 illustrates a low power data storage system in accordance with the present invention.

FIG 2 illustrates configuration of a low power data storage system in accordance with the present invention.

FIG 3 illustrates each operational mode of a storage medium that is performed by a write control means in accordance with the present invention.

FIG 4a illustrates one example of data received at different time and FIG 4b illustrates one example of data accumulated in a buffer module of the present invention. FIG 5a illustrates one embodiment of a buffer module in accordance with the present invention.

FIG 5b illustrates change of the size of data accumulated in a buffer module that includes at least one unit buffer in accordance with the present invention.

FIG 6a illustrates the pattern of power consumed in storing data in accordance with the prior art and FIG 6b illustrates the pattern of power consumed in storing data in accordance with the present invention.

FIG 7 illustrates a flow chart for describing a low power data storage method in accordance with one preferred embodiment of the present invention.

FIG. 8 illustrates a flow chart for describing a data storage method in accordance with other embodiment of the present invention.

FIG 9 illustrates a block diagram of a general purpose computer that can be adopted in performing a low power storage method in accordance with the present invention.

Disclosure of the Invention

Technical Questions The present invention is conceived to solve the aforementioned problems of the prior art. The object of the present invention is to provide a energy efficient data storage system and method that accumulates the data received via a receiving means into a predetermined temporary memory device and controls the operation of a storage medium on the basis of the size of the accumulated data or time that is required for accumulating data, thereby completely excluding an idle mode of the storage medium that blindly waits for a storage command.

It is another object of the present invention to provide a low power data storage system and method that performs a stable write process by determining a write size S and a write time Tw on the basis of characteristics of operation modes of a storage medium and data recording rate and by quantitatively determining the size of data written for one continued write mode. The present invention also exactly determines the triggering point of a storage command and the duration of each operation mode.

It is still another object of the present invention to provide a low power data storage system and method that facilitates design and maintenance of a buffer by determining a buffer size B on the basis of a write size S, and exactly measures the triggering point of a storage command and a continuation time of each operation mode.

It is another object of the present invention to provide a low power data storage system and method that guarantees smooth transfer process of continuously input data by arranging a plurality of buffers between data, which are generated either synchronously or asynchronously, and asynchronously operating storage medium, and accumulates data with the predetermined write size S, thereby securing a stable write process.

Technical Solutions In order to achieve the aforementioned objects, a low power data storage system in accordance with one embodiment of the present invention comprises a data receiving means for receiving data generated by a signal processing; a data transferring means for transferring the received data to a buffer module, thereby accumulating the same therein; and, a write control means for abstracting a predetermined size of data from the buffer module and writing the same in a storage medium; wherein the write control means controls data to start being written when the predetermined size of data are accumulated in the buffer module, and the storage medium to be transited to an initial state immediately after finishing writing the abstracted data.

A low power data storage method in accordance with one embodiment of the present invention comprises the steps of receiving data generated by a signal processing; transferring the received data to a buffer module, thereby accumulating the same therein; and abstracting a predetermined size of data from the buffer module and writing the same in a storage medium in accordance with a storage command that is triggered when a stand-by mode time To passes from the time when the data starts being transferred into the buffer module, wherein the step of transferring the received data comprises the steps of determining the size of data to be written for a predetermined write mode time Tw as a write size S; and controls the data corresponding to the determined write size S to be accumulated in the buffer module, and the write mode time Tw satisfies the following two conditions,

> ^^TS ^+Tf ) ^{* r}

R-r and

( ._L_. (W_s+W_r (T_s+Tf ) - P₀) . r ) τ > w- ' o

R-r

wherein the Ts is a length of start-up mode, the R is storing rate, the Tf is a length of finish mode and the r is transfer rate.

A low power data storage method in accordance with another embodiment of the present invention comprises the steps of receiving data generated by a signal processing; transferring the received data to a buffer module, thereby accumulating the same therein; and abstracting a predetermined size of data from the buffer module and writing the same in a storage medium in accordance with a storage command that is triggered when the size of data accumulated in the buffer module reaches m, wherein the step of transferring the received data to the buffer module comprises the steps of determining a predetermined buffer size B as a write size S corresponding to the size of data written in the write mode of the storage media; and controlling the data corresponding to the determined write size S to be accumulated in the buffer module, and the buffer size B satisfies the following two conditions,

^{B ≥ T}W ^{• R} and

P_W- P₀ - ζ _s + W_f - (T_s +T_f ⁾ - P₀ ) B >

V r R ) wherein the Tw is a write mode time and R is storing rate.

Best Mode for Carrying Out the Invention

Hereinafter, a low power data storage system and method will be described with reference to the accompanying drawings.

FIG. 1 schematically illustrates a low power data storage system in accordance with the present invention.

A low power data storage system 100, which receives data generated by a signal processing and then writes and stores the received data in a storage medium 110 with the lower power than the prior art, and writes the data contained in a terminal means. This terminal means comprises a processing means for performing a predetermined calculations and a communication means for communication. For example, this terminal means might be a personal computer, a notebook computer, a mobile communication terminal (a cellular phone, a PDA and so on), a home appliance and the like having data storing functions.

Data comprises any kind of information and is transmitted to the storage medium 110 for writing and storing the information. For example, data might comprise voice data, image/moving picture data and information data such as a document or program. The data can be generated by a signal processing of an application program related to data generation, and executed in a data generating terminal means, such as a microphone, a camera, a personal computer and so on. In particular, the application program related to data generation may encode the generated data into an optimum type of a signal (for example, a digital signal) in order to transmit and store the information in the storage medium 110 without loss or distortion. The storage medium 110 is a device that records and stores generated data. For example, the medium may comprise a magnetic medium such as a hard disc, a floppy disc and a magnetic tape that usually used in a personal computer, an optical medium such as a CD-ROM and DVD, a magnetic-optical medium such as floptical disc, ROM, RAM and flash memory and so on. The low power data storage system 100 in accordance with the present invention can be applicable to any kind of storage medium that records and stores any type of data. Even though a magnetic disc or optical disc is adopted in the following embodiments of the present invention, the present invention is not limited or defined thereby. Therefore, other embodiments that adopt a storage medium except a magnetic disc or an optical disc can be easily induced from the present invention without departing from the scope of the present invention. The low power data storage system 100 will be in detail described with reference to FIG 2.

A low power data storage system 200 of the present invention comprises a data receiving means 210, a data transferring means 220, a write control means 230 and a buffer module 240. The data receiving means 210 receives data generated by a signal processing.

The data receiving means 210 might be a data receiving apparatus such as a modem, a LAN card, a wireless access card and so on, or a data collecting apparatus that collects data upon the data being generated by an application program that is executed in the same terminal means. The data received by the data receiving means 210 is transferred to the buffer module 240 according to a predetermined storage command.

The data transferring means 220 transfers the received data to the buffer module 240 and accumulates the same into the buffer module 240 and enables the transferred data to be accumulated in the buffer module 240. In addition, the data transferring means 220 determines a predetermined size of data written in a write mode of the storage medium 110 as a write size S and controls data corresponding to the determined write size S to be transferred to the buffer module 240. The write size S will be described in detail later.

The write control means 230 performs a signal processing in the direction reverse to that of the data transferring means 220. That is, the write control means 230 triggers a storage command at a predetermined time according to the size of data accumulated in the buffer module 240, and abstracts data from the buffer module 240 according to the generated storage command. At this time, the rate at which data is abstracted from the storage medium 110 is determined by a storing rate R of the storage medium 110. The storing rate R might vary in accordance with the data recording capability that is determined by manufacturing characteristics of the storage medium 110. In particular, the write control means 230 controls the storage medium 110 to be transited to an initial state immediately after finishing writing the abstracted data in the storage medium 110. That is, according to the control of the write control means 230, the storage medium 110 is operated in a finish mode in a manner that it is directly transited to a stand-by mode without an idle mode after finishing a write mode. Therefore, the power consumed for maintaining an idle mode of the storage medium 110 is not required, thereby saving a lot of power. Each operation mode of the storage medium 110 is described in detail with reference to FIG 3a.

FIG 3 a illustrates each operational mode of a storage medium that is controlled by a write control means in accordance with the present invention.

As shown in FIG 3 a, the write control means 230 controls the storage medium 110 to sequentially perform a stand-by mode 310 and a write mode 330, thereby storing data in the storage medium 110. In particular, the write control means 230 excludes an idle mode that continuously waits for data to be stored in the state of a high voltage applied, thereby preventing unnecessary power consumption of the storage medium 110. In the meantime, the start-up 320 is the step of transition from the stand-by mode 310 to the write mode 330 and the finish mode 340 is the step of transition from the write mode 330 to the stand-by mode 310.

A storage command might be the command for storing the predetermined data accumulated in the buffer module 240 into the storage medium 110 according to the data storing function that is activated for storage and maintenance of data generated by an application program related to data generation.

First, the stand-by mode 310 is a process for maintaining the storage medium 110 in an initial stage. Therefore, the basic power is approved and the stand-by mode 310 may mean an operation of the storage medium 110 in the section of waiting the next storage command (refer to To in FIG. 3 a). In the start-up mode 320, the storage medium 110 is transited from an initial state to the write mode 330 according to the data storing function. For example, if the storage medium 110 is a hard disc such as one type of a magnetic disc, the storage medium 110 in the start-up mode 320 spins up a platter that is in a standstill and performs a focusing and tracking. That is, in the start-up mode 320, a predetermined level of voltage is applied to the storage medium 110 and data becomes ready to be written. The start-up mode 320 might mean an operation of the storage medium 110 for the time when data cannot be written due to an unstable voltage curve that particularly appears on applying an initial voltage (refer to Ts in FIG 3a).

The write mode 330 writes the data accumulated in the buffer module 240 into the storage medium 110. That is, the write mode 330 determines the point when the storage medium 110 in the state of the stand-by mode 310 is transited to the state of storing data, i.e., the point verifying/verified in the write control mode (200) as the starting point of the write mode 330. Therefore, the write mode 330 might mean operation of the storage medium 110 for the time when an applied voltage is stable (refer to Tw in FIG 3a). Hereinafter, a power consuming pattern of the present invention in a write mode and that of the prior art in a read mode will be described with reference to FIG. 3b.

FIG 3b illustrates an exemplary pattern of power of the present invention consumed in a write mode. As shown in FIG 3b, a storage command is triggered at the point SI when predetermined data (for example, data satisfying a write size S) is accumulated in the buffer module 240. If the storage command is triggered at the point SI, the write control means 230 is controlled in such a way that a certain process may be performed, such as that the storage medium 110 drives a disc platter in a standstill at a normal speed by focusing and tracking a disc head of a hard disc from a parking to the predetermined position of the storage medium 110. Therefore, due to the characteristics of the transition S2-S3 in FIG. 3bshow a pattern of unstable power approval.

The write control means 230 triggers a predetermined termination signal for terminating the write mode 330 of the storage medium 110 at the point S3 when the abstracted data finishes being written. The termination signal transits the storage medium 110 from a normal operation state to a stand-by state. In case of a hard disc, if the termination signal is generated, a disc head is parked at an initial position and a disc platter rotates at a lower speed or becomes standstill.

In the finish mode 340, the storage medium 110 is transited to an initial state when the abstracted data finishes being written. The finish mode 340 might mean the operation of the storage medium 110 during an unstable time-delay period where applied power is reduced in accordance with termination of the write mode 330 (refer to Tf in FIG 3a). In this mode, a hard disc platter goes spin-down and slowly stops, and a disc head is parked.

The buffer module 240 buffers inconsistence of data stream between the data transferring means 220 and the write control means 230. The inconsistence of data steam occurs due to the difference of a data processing rate, a processing unit, a processing time and so on between the data transferring means 220 and the write control means 230. In particular, the buffer module 240 accumulates irregularly input data and, if a storage command occurs, abstracts the data accumulated in the buffer module 240. Therefore, the buffer module 240 improves efficiency of power consumed for driving the storing medium 110 and storing data. The process of accumulating data in the buffer module 240 and process of abstracting data from the buffer module 240 is described with reference to FIGs. 4a and 4b.

FIG 4a illustrates one example of data received at different time and FIG 4b illustrates one example of data accumulated in a buffer module of the present invention. As shown in FIG 4a, data transferred into a buffer in accordance with a data storing function is not periodically input and varies in the size thereof due to the difference of a terminal means generating data and to the data generating conditions. If the storage medium 110 writes the irregularly input data every time the same is input, a storage command is frequently triggered. In order to process this storage command, the storage medium 110 is, for example, operated continuously in the write mode 330 or each operation mode is continuously repeated. Both of these processing methods consume a lot of power. In addition, the size of the data written in the write mode 330 varies because input data is written as they are, thereby deteriorating a stable write process. That is, as shown in FIG 4a, the storage command is triggered four times in order to write each data that is input at four different points and the voltage applied to the storage medium 110 is maintained for the period PI. In order to solve this inefficient write process, the buffer module 240 of the present invention, as shown in FIG 4a, accumulates irregularly input data up to a write size S in accordance with a predetermined condition, and collectively transfers the accumulated data to the storage medium 110 in accordance with a storage command that is triggered when data is accumulated up to the write size S. In FIG 4b, the data transferring means 220 transfers four data to the buffer module 240. For example, if total size of four accumulated data is large enough (for example, satisfying the write size S), the write control means 230 collectively abstracts four accumulated data from the buffer by a series of consecutive storage commands and then writes the same in the storage medium 110. A collective write process might mean a process that writes data by consecutively executing a generated storage command without going through any additional stand-by mode 310 or an idle mode after the storage medium 110 starts to operate in the start-up mode 320. According to this method, as shown in FIG 4b, power is applied during the period P2 that is shorter than PI and, therefore, low power data storage is implemented. Therefore, the low power data storage system 200 that adopts the buffer module 240 in accordance with the present invention prevents the storage medium 110 from unnecessarily running idle when it writes a series of data, so that umiecessary power consumption is minimized. Further, the low power data storage system 200 of the present invention writes data into the storage medium 110, so that uniform storage bandwidth as required can be stably provided, wherein the data is accumulated up to a uniform size (write size S) in accordance with predetermined conditions.

The buffer module 240 guarantees the uniform size of the data (write size S) to be stored by consecutive write modes 330 in relation to the operation of the write mode 330 of the storage medium 110, so that the triggering point of a storage command (the point when the storage medium 110 is switched from the start-up mode 320 to the write mode 330, as shown as SI in FIG 3b) and continuation time of the write mode 330 can be precisely anticipated. For this purpose, it is important to appropriately determine the write size S of the data accumulated in the buffer module 240. If the write size S is too large, it takes long to accumulate data and I/O latency becomes long, thereby deteriorating I/O performance. On the other hand, if the write size S is too small, it takes too much time for transition of operation modes due to frequent transition between the write mode 330 and the stand-by mode 310. The buffer module 240, which is a temporary memory space that is assigned in a predetermined memory storing data, is a consecutive or nonconsecutive memory space that stores data having at least write size S. One embodiment of this buffer module 240 might comprise at least one unit buffer having a predetermined buffer size B. In this embodiment, the data having the selected write size S is accumulated in the unit buffers. The reason for adopting at least one unit buffer is that the operation that temporarily writes data in the buffer module 240 for maintaining data consistency cannot be performed on the same buffer module 240 simultaneously with the operation of reading data from the buffer module 240 and storing the same in the storage medium 110. That is, the buffer module 240 might be configured to have a plurality of unit buffers in order to transfer and store data continuously. The data transferring means 220 accumulates data input into the buffer module 240 and the write control means 230 drives the storage medium 110 to perform a write process if sufficient data (at least write size S) is accumulated in the buffer module 240. If the write process is completed, the write control means 230 controls the storage medium 110 to operate in the stand-by mode 310 and prevents the storage medium 110 from running idle by repeating these processes. The buffer size B is preferable to be at least write size S. In the following, a selected criterion determining the write size S will be described.

The selected criterion, which determines the write size S of data written in the write mode 330, is either the write mode time Tw or the buffer size B of the buffer module. It is described with reference to FIGs 3a, 5a and 5b.

As described above, the object of the present invention is to maximize power efficiency by controlling operation modes of the storage medium 110 by considering the condition that data stored in the storage medium 110 is transferred into the buffer module 240. The operation mode of the storage medium 110 repeats the start-up mode 320, the write mode 330, the finish mode 340 and the stand-by mode 310. An operation cycle period is defined by the period from the start-up mode 320 to the standby mode 310. As described above, the write control means 230 controls each operation mode of the storage medium 110 to minimize power consumed in the write process. The write control means 230 controls the storage medium 110 to operate in the start-up mode 320 on the basis of size of data accumulated in the buffer module 240 and terminates the write mode 330 of the storage medium 110 on the basis of size of data abstracted from the buffer module 240. In another embodiment of the present invention, the write control means 230 controls the storage medium 110 to operate in the start-up mode 320 on the basis of the time that is taken to accumulate data in the storage medium 110 and terminates the write mode 330 of the storage medium 110 on the basis of the time that the write mode 330 is continued. This control method might adopt interrupting, polling, a system call and the like. Both control methods, each of which is based upon the size of accumulated data or time respectively, assume that data transfer rate is uniform, i.e., the size of data transferred per second is uniform.

Determination of a write mode time Tw

One example of determining a write size S on the basis of a write mode time Tw will be described.

FIG 5a illustrates one embodiment of a buffer module 500 in accordance with the present invention. As shown in FIG 5 a, it is assumed that the transfer rate at which the data is transferred into the buffer module 500 is r and the storing rate at which data is abstracted from the buffer module 500 and stored in the predetermined storage medium 110 is R. In a preferred embodiment of the present invention, the buffer module 500 has a storing rate R that is larger than a transfer rate r. This condition prevents overflow of the buffer module 500. If the transfer rate r is larger than the storing rate R under the conditions that data is continuously transferred into the buffer module 500, data is incrementally accumulated therein, thereby occurring data overflow and data cannot be transferred any more. This overflow deteriorates the performance of a micro processor (CPU) that carries out a signal processing of data, so that data cannot be generated continuously or that generated data is lost. The write mode time Tw is determined by considering the following parameters of the storage medium 110, i.e., a start-up mode time Ts, a finish mode time Tf, a storing rate R and power consumed in each operation mode. With reference to FIGs. 3a and 5a, the write mode time Tw will be induced in the following.

As shown in FIG 5a, if generated data is transferred into the buffer module 240 at the uniform transfer rate r, the size of the data transferred into the buffer module 500 and the size of the data abstracted from the buffer module 500 have the following relationship.

T_w ^• R > Td ^■ r i f . τ_s+τ_w+τ_f = τ_d

Td is a time period that is directly related to data storage and is defined by the time that deducts a stand-by mode time Ts from a cycle period T of the write control means 230. That is, Td is defined by start-up mode time Ts + write mode time Tw + finish mode time Tf. Formula 1 means that the size of the data abstracted from the buffer module 500 is same to or larger than the size of data transferred into the buffer module 500. In view of FIG 3a, formula 1 explains that the size of data abstracted for Td is same to or larger than the size of data transferred for T (T>Td). This condition can be induced from the characteristics of the buffer module 240 where the transfer rate r has to be smaller than the storing rate R in order to prevent buffer overflow.

By rearranging formula 1 in terms of the write mode time Tw, the write mode time Tw is defined by the following formula 2. <Formula 2>

_T -> ^{( τ}s +^τf > ^{• r}

¹ =≥ j__r

The write mode time Tw defined in formula 2 means the time for which the write mode 330 is maintained. A write size S can be determined by considering the transfer rate r and the storing rate R in the data transferring means 220. If Tw is assumed to be one of the Tw that satisfies formula 2, the operation cycle period T of an operation mode of the storage medium 110 becomes T = Ts + Tw + Tf + To. From this condition, the following formula 3 is induced.

T_w*- R = (T_w*+T_s+T_f +T₀ ) τ Formula 3 is induced under the assumption that the size of the data transferred for one operation cycle period T is equal to the size of the data abstracted. By rearranging formula 3 in terms of Tw , To of the following formula 4 is decided. <Formula 4>

_ T_w*- R - (T_w*+T_s+T_f ) - r o r Therefore, the present invention might be designed to trigger a storage command after the stand-by mode time To passes from the time when data starts being transferred to the buffer module 500, and control the storage medium 110 so that a write mode can be maintained during the write mode time Tw. The start-up mode time Ts and the finish mode time Tf, which are shown in FIG 3a, have fixed values that are determined by manufacturing characteristics of the storage medium 110, and the write mode time Tw and the stand-by mode time To can be calculated by using formulas 2 and

4 respectively. Accordingly, the data transferring means 220 determines the write size

5 that corresponds to the size of RxTw under the condition of Tw>0, and performs a transfer process so that the data with the determined write size S is to be written in the buffer module 500. The low power data storage system 200 controls the data transferring means 220 to transfer data to the buffer module 500 for the stand-by mode time To. The low power data storage system 200 also controls the write control means 230 to abstract accumulated data from the buffer module 500 for the write mode time Tw (transferred data size = abstracted data size). These operations enable a low power data storage system of the present invention even when the buffer module 500 is comprised of one buffer unit.

Therefore, an operation mode control for writing data can be optimized by exactly determining the write mode time Tw and the stand-by mode time To in accordance with the present invention, and an uniform size of data, i.e., the write size S is abstracted from the buffer module 500 (or transferred to the buffer module 500) by maintaining a write mode for the write mode time Tw. Furthermore, the present invention can exclude an idle mode of the storage medium 110 that vaguely waits for the next storage command by exactly anticipating a triggering point of a storage command on the basis of the calculated stand-by mode time To, thereby implementing a low power data storage system.

Determination of a buffer size B

According to another embodiment of the present invention, a write size S might be determined on the basis of not only a write mode time Tw but also a buffer size B that is the size of data accumulated in the buffer module 240.

The buffer size B might mean the capacity of a unit buffer that is included in the buffer module or the size of data (write size S) that is written while the write mode 330 of the storage medium 110 is maintained. The write control means 230 of the present invention controls the write mode 330 to be executed, if the size of the data accumulated in the buffer module 240 reaches a critical value, and the data accumulated in the buffer module to be abstracted. If the size of the data remaining in the buffer module 240 goes below the critical value, the write control means 230 terminates a write mode. At this time, the size of the data written into the storage medium 110 for one period of the write mode 330 is called the write size S. In one embodiment of the present invention, the buffer size B of a unit buffer might be determined to be the write size S. In this case, if data accumulation is completed in a predetermined unit buffer, newly received data is transferred to another unit buffer and the data of which the accumulation is completed in the unit buffer is stored in the storage medium 110. The write size S can be conveniently determined if the buffer size B is preferably set to be the maximum capacity of a unit buffer. However, since the maximum capacity of a unit buffer might slightly vary in each unit buffer due to the difference of manufacturing characteristics therebetween, the buffer size B is determined to have a proper value below the maximum capacity of a unit buffer. FIG 5b illustrates change of the data size accumulated in a buffer module that includes at least one unit buffer in accordance with one embodiment of the present invention. As shown in FIG 5b, the buffer module 500 includes three unit buffers (from a first to a third unit buffer) 510, 520 and 530. The buffer size B of each of the unit buffers 510, 520 and 530 is determined to be the write size S of the data written in the storage medium 110. In this embodiment, the data transferred into the buffer module 500 is transferred into the first unit buffer 510 and, if the size of the data accumulated in the first unit buffer 510 reaches the write size S, data is transferred into the second unit buffer 520. In this way, data is repeatedly transferred into the unit buffers in the sequence of a first unit buffer → a second unit buffer → a third unit buffer → ....

As shown in FIG 5b, each of unit buffers 510, 520 and 530 has virtual search lines of accumulated data such as m and m . For example, if data size accumulated in each of unit buffers 510, 520 and 530 reaches m (ml, m2 or m3), the write control means 230 triggers a storage command and controls the storage medium 110 to operate in a start-up mode. On the other hand, if the data size accumulated in each of unit buffers 510, 520 and 530 reaches m (ml ,m2 ,m3 ), the write control means 230 triggers a termination command (or without triggering a storage command) and controls the storage medium 110 to operate in the finish mode 340.

The search lines of data accumulation m and m might be determined properly on the basis of the transfer rate r, the storing rate R, the start-up mode time Ts, the finish mode time Tf, a buffer size and so on. In one embodiment, the write control means 230 might determine m on the basis of the transfer rate r at which data is transferred into unit buffers 510, 520 and 530 of the buffer module 240, and determine m on the basis of the storing rate R, at which data is abstracted from the buffer module 240. Accordingly, a storage command is triggered when data accumulated in unit buffers 510, 520 and 530 of the buffer module 240 reaches m, and a write mode of the storage medium 110 is terminated when the accumulated data reaches m , so that an executing point of each operation mode of the storage medium 110 can be precisely determined and the operation modes of the storage medium 110 can be controlled on the basis of this determination. Hereinafter, data accumulation in unit buffers 510, 520 and 530 and operation of the storage medium 110 in relation thereto will be described with reference to FIG. 5b.

In FIG 5b, the data transferring means 220 transfers data into the first unit buffer 510 at the transfer rate r in accordance with a transfer sequence. When data transfer is in progress and the data size accumulated in the first unit buffer 510 reaches ml, the write control means 230 triggers a storage command and controls the storage medium 110 to operate in the start-up mode 320. At this time, ml is set on the basis of the buffer size B, the start-up mode time Ts, the transfer rate r and so on. For example, in FIG 5b, it is possible to properly set ml so that the size of the data accumulated in the first unit buffer 510 during 'To + Ts' may reach the buffer size B (write size S). In this embodiment, m(ml, m.2, m3) is set at the position where the data accumulation is not completed by considering a completing point of data accumulation. However, this is merely one exemplary embodiment of the present invention and it is to be noted that there are other various setting methods. For example, m(ml, m2, m3) can be set at a position corresponding to the buffer size B or at a predetermined position of the unit buffer 520 that has the next transfer sequence. As shown in FIG 5b, the degree of variation in the accumulated data size might be different based on these various setting methods. This can be easily understood from the embodiment of the present. As shown in FIG 5b, a write mode of the storage medium 110 becomes operable on accumulated data if the storage medium 110 starts to operate in a start-up mode, predetermined time (for example, the start-up mode time Ts) passes, and data finishes being accumulated in the first unit buffer 510. At this time, the data transferring means 220 finishes transferring data into the first unit buffer 510 and then starts transferring data into the second unit buffer 520 according to the transferring sequence. The write control means 230 determines whether the data accumulated in the first unit buffer 510 reaches the write size S and, if so, the write control means 230 starts abstracting the accumulated data at the storing rate R. Total data accumulated in the buffer module (240) is reduced to the rate of R-r and the write control means 230 maintains the write mode of the storage medium 110 for Tw. As mentioned above, while the data accumulated in the first unit buffer 510 is abstracted, data is being accumulated into the second unit buffer 520. If the size of the data accumulated in the second unit buffer 520 reaches m2 , the write control means 230 terminates the write mode of the storage medium 110. m2 is determined on the basis of the reducing rate R-r of the data accumulated in the buffer module 240 and the buffer size B. For example, m2 can be determined on the basis of the size of the data accumulated into the second unit buffer 520 at the transfer rate r when all the data accumulated in the first unit buffer 510 are abstracted. That is, m (ml , m2 , m3 ) is preferred to be determined by considering the point when all the data to be abstracted by a preceding storage command are abstracted from a predetermined buffer. As shown in FIG 5b, the gradient of the data reducing rate R-r is steeper than that of the transfer rate r and, therefore, the characteristics of the buffer module 240, a transfer rate r < a storing rate R, is satisfied. Then, the storage medium 110 is be transited to a stand-by mode after the predetermined finish mode Tf (not shown) and is transited to a stand-by mode. The write control means 230 determines whether the data accumulated in the second unit buffer 520 reaches m2 and waits for the next storage command.

Accordingly, the buffer module 240 of the present invention comprises a plurality of the unit buffers 510, 520 and 530 and continuously transfers data. In addition, the present invention facilitates design and data management by determining the write size S as the buffer size B of the unit buffers 510, 520 and 530.

A formula for the aforementioned buffer size will be induced in the following. As shown in FIG 5b, the buffer size B satisfies the following formula 5 if a transfer rate to the buffer module 240 is r and a storing rate into the buffer module 240 is R.

B > T_w ^• R Formula 5 means that the buffer size B of the unit buffers 510, 520 and 530 is the same to or larger than that of the data written in the write mode 330, and, more specifically, it means that there must be data to be recorded for the write mode time Tw and there is no idle state. If the left and right side is equal in formula 5, the maximum capacity of the unit buffers 510, 520 and 530 might be set as the write size S. In this case, since the write size S, the write mode time Tw and the stand-by mode time To of the storage medium 110 might be simply determined, the write control means 230 of the present invention can be conveniently designed. Since the write mode time Tw in formula 5 can be induced as the same way in formula 2, the detailed description will be omitted. The low power data storage system 200 of the present invention transfers data into the unit buffers 510, 520 and 530 of the buffer module 240 in accordance with the predetermined transfer sequence. If the size of the data accumulated in one unit buffer (for example, the first unit buffer 510) which is included in the buffer module 500 exceeds the buffer size B, it is possible to enable data to be transferred into the next sequence unit buffer (for example, the second unit buffer 520). At this time, as the size of the data accumulated in the first unit buffer 510 reaches the buffer size B, the data starts being abstracted from the first unit buffer 510. Accordingly, it is possible to guarantee continuous data transfer, suppress buffer overflow which deteriorates data generation, and perform a stable write process by determining the uniform write size S. A low power data storage method in accordance with the present invention will be described with reference to FIGs. 6a and 6b.

As described above, there might be two methods for storing data into the storage medium 110. The first storage method is the method where the storage medium 110 is operated in an idle mode and transited to a write mode whenever data is input (refer to FIG 6a) (hereinafter, the first storage method) and the second one is the method where data is written by periodically repeating each operation mode (a start-up mode, a write mode, a finish mode and a stand-by mode) (refer to FIG 6b) (hereinafter, the second storing method). If the write size S (that is, the buffer size B) is not large enough, since a unit buffer finishes accumulating data in short time, the operation cycle period T of the storage medium 110 becomes short, whereby power consumption might inefficiently increases due to the frequent transition between the operation modes (for example, the start-up mode or finish mode). Therefore, the write size S should be determined on the basis of the data transfer rate r, the storing rate R, continuation time of each operation mode Ts, Tw, Tf and To, and amount of power consumption related thereto. FIG 6a illustrates the pattern of power consumed in storing data in accordance with the prior art and FIG 6b illustrates the pattern of power consumed in storing data in accordance with the present invention.

In FIGs 6a and 6b, it is assumed that the capacity of a unit buffer is the buffer size B, and both the size of the data transferred into the unit buffer and that of the data abstracted from the unit buffer after predetermined accumulating time are same to the buffer size B. That is, referring to FIG 5a, it is assumed that the data having the buffer size B is accumulated into the unit buffer during the stand-by mode time To, and the accumulated data is abstracted from the unit buffer for the write mode time Tw*.

Under these conditions, one operation cycle period T can be expressed in the following formula 6. <Formula 6>

T = ( T_s+T_f +T₀ + T_w* )

The relation between the data size B abstracted form the unit buffer and the storing rate R of the storing medium 110 can be expressed as the following formula 7. <Formula 7>

B

I W W —- R

If the data size B transferred into the unit buffer is expressed in terms of the transfer rate r, B is defined by T-r, that is, B=T r. If formulas 6 and 7 are substituted into this equation, the following equations are induced. B = (Ts+Tf+To+Tw*)-r

<=> B/r = (Ts+Tf+To+(B R)) From this equation, the stand-by mode time To can be expressed as formula 8.

If each operation mode of the storage medium 110 is performed in accordance with the first storage method, the amount of power consumed W, which is shown in FIG 6b, can be defined by formula 9. Po, Ws, Wf and Pw are power consumed in the stand-by mode, the start-up mode, the finish mode and the write mode respectively.

W = T₀- Po+W_s + W_f +T_W~ - P_W

In addition, if each operation mode of the storage medium 110 is performed in accordance with the second storage method, the amount of power consumed W¹, which is shown in FIG 6a, can be expressed by formula 10.

In order to prove that the present invention improves efficiency of low power consumption, the amount of power consumed in the first storage method should be smaller than the amount of power consumed in the second storage method, or formula 9 < formula 10. This condition results in the following inequity. To-Po + Ws + Wf + Tw*-Pw < (To + Ts + Tw* + Tf)-Pw

<=> [B-((l/r)-(l/R))-(Ts+Tf)]-Po + Ws + Wf < [B-((l/r)-(l/R))]-Pw

<=> Ws + Wf - (Ts+Tf)-Po < [B-((l/r)-(l R))]-(Pw-Po)

If this inequity is rearranged in terms of the buffer size B, the following formula 11 is induced. Formula 11 defines the condition of the optimum buffer size B of a unit buffer for saving power consumption.

.( _s+W_f- (T_s+Tf ) ' P₀)

Pw-^po

There is a case that the buffer size B is prefixed in a predetermined storage medium, e.g., a hardware that is manufactured according to normal specifications. It is preferable that a storage system with the buffer size B selectively adopts a storage method of minimizing power consumption in accordance with the size of input data. For example, the storing method can be selected through formula 12 that is induced by comparing formula 9 (the first storing method) and formula 10 (the second storage method). <Formula 12>

To-Po + Ws + Wf + Tw*-Pw < (To + Ts + Tw* + Tf)-Pw

In other words, if formula 12 is effected (when the data size accumulated in the buffer module 240 is large enough), the first storage method can be adopted in a mamier that the storage medium 110 is controlled to repeatedly perform operation modes without an idle mode. On the other hand, if formula 12 is not effected (when the data size accumulated in the buffer module 240 is not large enough), the second storage method can be adopted in a manner that the storage medium 110 is controlled to write data by repeatedly performing a write mode and an idle mode as like in the prior art.

The write mode time Tw in view of power consumption can be induced from formula 11.

( p^p - ^+Wf- ^+Tf ϊ . Po) ^ )

Tw > W

R-r

Formula 13 is induced by applying the equation B=Tw-R to formula 11 and rearranging formula 11 in terms of Tw. Accordingly, the write mode time Tw can be expressed not only in terms of time but also in terms of power.

Therefore, the low power data storage system 200 of the present invention can completely exclude an idle of the storage medium 110 consuming unnecessary power by precisely determining the generation point of a write mode and continuation time of the storage medium 110. It also guarantees a stable write process by providing a uniform size of data that is to be written by a predetermined storage command.

Furthermore, contrary to the prior art, the capacity of the buffer module might be designed to satisfy the condition of formula 11 when a computer system is designed.

Or, a data storing system in accordance with the present might be selectively implemented if the capacity of the buffer module satisfies the condition defined by formula 11. Or a buffer might be temporarily assigned in order for the capacity of the buffer module to satisfy the condition of formula 11. It is evident to those skilled in the art that other various methods are also applicable.

Furthermore, the present invention can determine precisely continuation time of each operation mode, whereby the present invention can facilitate determination of the capacity of the buffer module 240, design of a unit buffer and assignment of a different accumulating capacity to each unit buffer and the like. A workflow of the low power data storage system 200 in accordance with the present invention will be described in detail.

A low power data storage method of the present invention is characterized by that the write mode time Tw and the buffer size B are determined on the basis of the criterion that determines the write size S to be processed in the write mode 330 of the storage medium 110. Each low power data storage method is implemented by the low power data storage system 200.

First, a low power data storage method based upon the selection of the write mode time Tw will be described with reference to FIG 7.

FIG 7 illustrates a flow chart for describing a low power data storage method in accordance with the present invention.

In step S710, the low power data storage system 200 determines the size of data to be written for the write mode time Tw. In step S710, the size of the data accumulated in the buffer module 240 is determined. If the buffer module 240 comprises at least one unit buffer having a predetermined capacity, the data transferring means 220 transfers and accumulates predetermined size of data that is to be written for the write mode time Tw into each unit buffer. The write mode time Tw can be induced from formulas 1 and 2 and satisfies the following conditions.

(T_s+T_f )

T_w > -

R-r or,

( p-V- ( ₈+ r (T_s+Tf ) - P₀) - r ) τ_w> W- ro

R-r In step S720, the low power data storage system 200 receives data that is generated by a signal processing. In this step, the low power data storage system 200 receives data that is generated by an application program related to data generation. The application program can be implemented in a remote data communication means (for example, a contents providing server, a voice/moving picture information providing device and so on) or a data generation terminal (for example, a camera and a microphone).

In step S730, the low power storage system 200 transfers the received data to the buffer module 240 through the data transfer means 220. In this step, data of the determined write size S is accumulated by transferring the same into the buffer module 240, on the basis of the predetermined criterion. Thus, data is sequentially accumulated in the unit buffer comprised in the buffer module 240 according to the predetermined transfer sequence.

In step S740, the low power data storage system 200 determines whether data accumulated in the buffer module 240 reaches the write size S. This step S740 is a process for determining whether sufficient size of data (over write size S) is accumulated in the buffer module 240.

If data accumulated in the predetermined unit buffer reaches write size S in the step S740 (Yes in step S740), the low power data storage system 200 triggers a storage command to expel corresponding accumulated data in step S750. This step S750 is a process for triggering a storage command after To passes from the point of time of data transfer into the buffer module 240. The accumulated data is written through the write mode of the storage medium 110. In addition, in this step, the size of the data accumulated in the buffer module 240 for the stand-by mode time To is determined to be the write size S for a write process and abstracted by the write control means 230. The stand-by mode time To can be induced from formulas 3 and 4 under the condition of Tw* satisfying the above inequity and is expressed as the following equation.

T ^T *' ^{R "} (T_w*+T_s+Tf ) τ ' o Γ

After data finishes being abstracted from the buffer module 240, the low power data storage system 200 determines whether there is any data input thereinto in step S760. In this step, it is determined whether there is any data written with respect to data generated by a data generation related application program. Thus, if there is input data, the low power data storage system 200 of the present invention transfers data to the buffer module 240 by going to step S730.

In addition, unless data accumulated in the predetermined unit buffer in the step S740 reaches the write size S (No in step S740), the low power data storage system 200 triggers a predetermined compulsory storage command and enables the storage medium 110 to write data accumulated in the buffer module 240 in step S770. In case that the size of data accumulated in the buffer module 240 for the stand-by mode time To does not reach the write size S, the step S770 is a process for writing remaining accumulated data. Therefore, the low power data storage system 200 of the present invention enables smooth abstraction of data by enabling abstraction with respect to data remaining in the buffer module 240 without abstraction since data size is smaller than the write size S.

The low power data storage method of the present invention writes the data which is transferred for the stand-by mode time To for the write mode time Tw, whereby it is possible to precisely determine continuation time of each operation mode of the storage medium 110. Therefore, the low power data storage method of the present invention makes it possible to completely exclude an idle mode that consumes unnecessary power.

The low power data storage method by determination of the buffer size B of the present invention will be described with reference to FIG. 8. FIG. 8 illustrates a flow chart for describing the low power storage method according to another embodiment of the present invention.

First, in step S810, the low power data storage system 200 determines the buffer size B as the write size S that is the size of data written in the write mode 330 of the storage medium 110 and controls the data corresponding to the determined write size S to be accumulated in the buffer module. In this step S810, the write size S is determined on the basis of a unit buffer of the buffer module 240. Data having the buffer size B is accumulated in one unit buffer and, if data accumulation is completed in one unit buffer, the data transferring means 220 performs a transfer process into the next unit buffer according to the transfer sequence. This buffer size B can be induced from formulas 2 and 5 and satisfies the following conditions.

B ≥ T_w ^• R v or,

That is, the buffer size B might be the size of the data written in the write mode of the storage medium 110 and the data transferring means 220 determines the uniform size of write data by accumulating as much data as the buffer size B into each unit buffer.

In step S820, the low power data storage system 200 receives data generated by a predetermined signal processing and in step S830, transfers the received data to the buffer module 240. These steps S820 and S830 correspond to the aforementioned steps S710 and S720. Thus, the detailed description will be omitted. However, in step S830, transfer with respect to data by the data transfer means 220 is controlled to be performed in predetermined transfer sequence and the size of data accumulated in one unit buffer is limited to the buffer size B. In step S840, the low power data storage system 200 determines whether the size of the data accumulated in the unit buffer of the buffer module 240 reaches m (ml, m2, m3) after the predetermined time passes. This step S840 is a process for determining whether the sufficient size of the data to be written when the storage medium 110 operates in a write mode, i.e. the write size S, is accumulated in the buffer module 240.

Then, if the size of the data accumulated in the predetermined unit buffer reaches m (ml, m2, m3) in the step S840 (Yes in step S840), the low power data storage system 200 generates a storage command to expel the corresponding accumulated data in step S850. In this step, the storage command is triggered by considering the time when the size of the data accumulated in a unit buffer reaches the buffer size B, i.e. the write size S, on the basis of the determined buffer size Band data is abstracted from the unit buffer that reaches the buffer size B. This process has been described in detail with reference to FIG 5b. As shown in FIG 5b, the triggering point of a storage command m and termination point of a write mode m* are flexibly determined on the basis of manufacturing characteristics of a unit buffer, the start-up mode time Ts of the storage medium 110, the transfer rate r, the storing rate R and so on.

After data finishes being abstracted from the buffer module 240, in step S860, the low power data storage system 200 determines whether there is data input into the low power data storage system 200. If there is input data, the low power data storage system 200 of the present invention transfers data to the buffer module by going to step S830.

In addition, if the size of the data accumulated in the predetermined unit buffer in the step S840 (No in step S840), the low power data storage system 200 generates predetermined compulsory storage command and enables the storage medium 110 to write data that is accumulated in the buffer module 240, in step S870.

Therefore, the low power data storage method of the present invention precisely measures the continuation time of the write mode on the basis of the triggering point of a storage command and the unit buffer that finishes accumulation, whereby it is possible to prevent an idle mode of the storage medium 110 that vaguely waits for a data storage command, thereby implementing a low power data storage.

The embodiments of the present might comprise a computer readable medium that comprises a program command for performing functions in various kinds of computers. The computer readable medium might comprise a program command, a data file, a data structure and the like or combination thereof. The media might be specifically designed or constituted for the present invention. The media might be the one that has been known to those skilled in the art. A computer readable medium might be a magnetic medium such as a hard disc, a floppy disc and a magnetic tape, an optical medium such as a CD-ROM and DVD, a magneto-optical medium such as floptical disc, a hardware device that is specially designed for storing and implementing a program command such as ROM, RAM and flash memory. The medium might be a transport medium such as an optical or metallic line and a waveguide that comprises a carrier signal that transports a signal designating a program command and data structure. A program command comprises machine language code generated by a compiler and high-level language code that can be executable through an interpreter in a computer. FIG 9 illustrates a block diagram of a general-purpose computer apparatus that performs a low power storage method in accordance with the present invention.

The computer device 900 comprises at least one processor 910 that is connected to the main memory that comprises RAM (Random Access Memory) 920 and ROM (Read Only Memory) 930. The processor 910 is sometimes called CPU. As well known in the technical field of the present invention, ROM 930 unilaterally transports data and instructions to a CPU. In general, RAM 920 bilaterally transports and receives data and instructions. RAM 920 and ROM 930 might comprise any type of appropriate computer readable media. The mass storage 940 is bilaterally connected to the processor 910 and provides an additional storage capacity. The mass storage 940 might be any type of a computer readable media. The mass storage 940 is used to store a program, data and the like. It is usually a secondary memory unit that is slower than a main memory like a hard disc. The mass storage like a CD ROM 960 might be used. The processor 910 is connected to at least one of an I/O devices 950 such as a video monitor, a trackball, a mouse, a keyboard, a microphone, a touch screen type display, a card detector, magnetic or paper tape interpreter, a voice or hand write detector, a joystick or other publicly known computer I/O device. The processor 910 might be connected to a wired or wireless communication network via the network interface 970. The aforementioned method can be implemented via this network connection. These device and instrument are well known to those skilled in the technical field of a computer hardware and software.

The above hardware device might be configured to operate as at least one software module for implementing the operation of the invention.

Although the present invention has been described in connection with the embodiments of the present invention illustrated in the accompanying drawings, it is not limited thereto since it will be apparent to those skilled in the art that various substitutions, modifications, and changes will be made without departing from the spirit and scope of the invention.

Industrial Applicability

As described above, the present invention provides a low power data storage system and method that accumulates the data received via a receiving means into a temporary memory device and controls the operation of a storage media on the basis of the size of the accumulated data or time that is required for accumulating data, thereby completely excluding an idle mode of a storage media that vaguely waits for a storage command.

In addition, the present invention provides a low power data storage system and method that performs a stable write process by determining a write size S and a write time Tw on the basis of performance characteristics of operation modes of a storage medium and data storing rate, and by quantitatively determining the size of data that is written in one of consecutive write modes. The present invention also exactly determines the triggering point of a storage command and a continuation time of each operation mode.

Furthermore, the present invention provides a low power data storage system and method that facilitates a design and maintenance of a buffer by determining a buffer size B on the basis of a write size S, and exactly measure the triggering point of a storage command and a continuation time of each operation mode.

Furthermore, the present invention provides a low power data storage system and data storage method that guarantees smooth transfer process of continuously input data by arranging a plurality of buffers between data, which are generated either synchronously or asynchronously, and a synchronously operating storage medium, and accumulate data of a uniform write size S, thereby securing a stable write process.

Claims

1. A low power data storage system comprising: a data receiving means for receiving data generated by a signal processing; a data transferring means for transferring the received data to a buffer module and accumulating the same therein according to a storage command; and, a write control means for abstracting the predetermined size of data from the buffer module and writing the same in a storage medium; wherein the write control means performs controls data to start being written when the predetermined size of data are accumulated in the buffer module, and the storage medium to be transited to an initial state immediately after finishing writing the abstracted data.

2. The low power data storage system according to claim 1, wherein the write control means controls the storage medium to sequentially perform the steps of: performing a start-up mode for transition to a write mode in accordance with the storage command; performing a write mode for writing the abstracted data in the storage medium; performing a finish mode for finishing recording the data and for transition to an initial state; and, performing a stand-by mode for waiting for the next storage command while maintaining the initial mode.

3. The low power data storage system according to claim 1, wherein the buffer module comprises at least one unit buffer having a predetermined buffer size B; and the data transferring means controls data corresponding to a predetermined write size S to be accumulated in the unit buffer based on a selected criterion; wherein the write size S means the data size being written in the write mode of the storage medium.

4. The low power data storage system according to claim 3, wherein the selected criterion is the write mode time Tw; the data transferring means determines the size of data that are to be written for the write mode time Tw as the write size S; and the write mode time Tw satisfies the following condition;

wherein Ts is a start-up mode time, R is storing rate, Tf is a finish mode time and r is transfer rate.

5. The low power data storage system according to claim 4, wherein the write mode time Tw further satisfies the following condition;

( _P _ _p ^» (W_S + W_f - (T_S+T_f ) - P₀ ) - r )

T > w-

R-r wherein the Po is power consumption in a stand-by mode, the Ws is power consumption in the step of being transited to a write mode, the Wf is power consumption in the step of being transited to an initial stage and the Pw is power consumption in a write mode.

6. The low power data storage system according to claim 5, wherein the storage command is triggered after the stand-by mode time To passes from the time when the data starts being transferred into the buffer module; and the stand-by mode time To satisfies the following condition;

wherein said Tw* is a predetermined write mode time satisfying the condition of the write mode time Tw; and the write control means controls the data accumulated in the unit buffer for the stand-by mode time To to be written for the write mode time Tw*.

7. The low power data storage system according to claim 3, wherein the selected criterion is the buffer size B of the storage medium; the data transferring means determines the buffer size B as the write size S; and the buffer size B satisfies the following condition;

B ≥ T_w ^• R wherein the Tw is a write mode time and the R is storing rate.

8. The low power data storage system according to claim 7, wherein the buffer size B further satisfies the following condition; (W_s + W_f - (T_S+T_f ) - P₀ ) - o

B

\ r R )

9. The low power data storage system according to claim 7, wherein the storage command is triggered when the size of the data accumulated in the unit buffer of the buffer module reaches m and continues when the amount of the data accumulated therein reaches m ; and said write control means sets m and m on the basis of at least one of the transfer rate r of the data transferred into said unit buffer of the buffer module, the storing rate R, the length of the start mode Ts, the length of the finish mode Tf, and power consumed in operation modes.

10. A low power data storage method comprising the steps of: receiving data generated by a signal processing; transferring the received data to a buffer module, thereby accumulating the same therein; and abstracting a predetermined size of data from the buffer module and writing the same in a storage medium in accordance with a storage command that is triggered when a stand-by mode time To passes from the time when the data starts being transferred into the buffer module; wherein the step of transferring the received data comprises the steps of determining the size of data written for a predetermined write mode time Tw as a write size S; and controlling the data corresponding to the determined write size S to be accumulated in the buffer module and the write mode time Tw satisfying the following two conditions,

(T_s +Tf ) - r

T > R-r and

( W_s+W_f - (T_S+Tf ) - P₀ ) τ ) τ_w > P w-- P' r o w

R-r wherein the Ts is a start-up mode time, the R is storing rate, the Tf is a finish mode time and r is transfer rate.

11. A low power data storage method comprising the steps of: receiving data generated by a signal processing; transferring the received data to a buffer module, thereby accumulating the received data therein; and abstracting a predetermined size of data from the buffer module and recording the predetermined size of data in a storage medium in accordance with a storage command that is triggered when the size of data accumulated in the buffer module reaches m„ wherein the step of transferring comprises the steps of determining a predetermined buffer size B as a write size S corresponding to the size of data written in the write mode of the storage medium; and controlling the data corresponding to the determined write size S to be accumulated in the buffer module and the buffer size B satisfies the following two conditions,

B j≥ T^ - and

-- ( Ws +Wf - ( T_s +Tf ) - Po >

B > " t 1_\ v r R J wherein the Tw is a write mode time and R is storing rate.

12. A computer-readable record medium that records a computer program for performing the method in accordance with claim 10 or 11.