Read-ahead Cache, Data buffer structure | Fujitsu MHU2100AT manual

Operations

6.4 Read-ahead Cache

Read-ahead Cache is the function for automatically reading data blocks upon completion of the read command in order to read data from disk media and save data block on a data buffer.

If a subsequent command requests reading of the read-ahead data, data on the data buffer can be transferred without accessing the disk media. As the result, faster data access becomes possible for the host.

6.4.1 DATA buffer structure

This device contains a data buffer. This buffer is divided into two areas: one area is used for MPU work, and the other is used as a read cache for another command. (See Figure 6.7)

a) 8MB buffer (8,388,608 bytes)

8,388,608 bytes

For MPU work

For R/W command

294,912

8,093,696

bytes

bytes

Figure 6.7 Data buffer structure

The read-ahead operation is done by the following commands.

•

•

•

READ SECTOR(S) (EXT)

READ MULTIPLE (EXT)

READ DMA (EXT)

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Fujitsu MHU2100AT manual Read-ahead Cache, Data buffer structure, 8MB buffer 8,388,608 bytes

Contents

MHU2100AT Disk Drive Product Manual For Safe Operation Handling of This Manual Revision History This page is intentionally left blank Preface Overview of Manual Operating Environment Conventions for Alert MessagesConventions Liability Exception This page is intentionally left blank Important Alert Items Important Alert Messages This page is intentionally left blank Manual Organization MHU2100AT Disk Drive Maintenance ManualMHU2100AT Disk Drive Product Manual This page is intentionally left blank Contents Installation Conditions Theory of Device Operation Contents Interface 100 120 Operations Glossary GL-1 Acronyms and Abbreviations AB-1 Index IN-1 Illustrations Figures Execution example of Read Multiple command Surface temperature measurement points and standard Tables 25 Relationship between combination of Identifier This page is intentionally left blank Device Overview Functions and performance FeaturesAdaptability Data buffer Error correction and retry by ECCConnection to ATA interface Read-ahead cache system Specifications summary Device SpecificationsSpecifications 1 MHU2100AT Specifications 2Model and product number Examples of model names and product numbers Input Voltage Power RequirementsRipple Current and power dissipation Power on/off sequence Environmental SpecificationsCurrent fluctuation Typ. at +5 V when power is turned on Environmental specifications Acoustic Noise Acoustic noise specificationShock and vibration specification Shock and Vibration Reliability Service lifeData assurance in the event of power failure Mean time between failures Mtbf Positioning error Error RateUnrecoverable read error Media Defects Advanced Power Management Advanced Power Management Advanced Power Management This page is intentionally left blank Device Configuration Device Configuration 2 1 drive connection System ConfigurationATA interface Read/write circuit 2 drives configuration 3 2 drives connection Installation Conditions Dimensions Dimensions Integration Guidance C141-E144 MountingOrientation Limitation of mounting FramePCA Location of breather Ambient temperature Service area Handling cautions Handling cautions Device connector Cable Connections Device connection Cable connector specificationsCable connector specifications FCI Power supply connector CN1 Jumper SettingsLocation of setting jumpers Factory default setting Master drive-slave drive setting Csel setting 14 Csel setting Power Up in Standby setting 16 Example 2 of Cable Select Theory of Device Operation Disk OutlineSubassemblies Spindle Servo circuit Circuit ConfigurationAir filter Spindle motor driver circuit Power Supply Configuration PCA Power-on Sequence Power-on operation sequence Self-calibration contents Self-calibration Command processing during self-calibration Execution timing of self-calibration Write circuit Read/write CircuitRead/write preamplifier PreAMP RLL code Meeprml AGC circuit Read circuitProgrammable filter circuit D converter circuit Digital PLL circuitFIR circuit Viterbi detection circuit Servo Control Servo control circuit Servo burst capture circuit Power amplifierMicroprocessor unit MPU A converter DAC Driver circuit Spindle motor control circuitVCM current sense resistor CSR Data area Data-surface servo formatInner guard band Outer guard band Physical sector servo configuration on disk surface Servo frame format Seek operation Actuator motor controlOperation to move the head to the reference cylinder Track following operation Stable rotation mode Start modeAcceleration mode Spindle motor control Theory of Device Operation Interface Interface signals Physical Interface DA1 PDIAG-, Cblid DA0 DA2 Signal assignment on the connectorSignal assignment on the interface connector Dasp GND Stop MstrDiow Dior Dasp PdiagCblid Iordy Logical Interface I/O registers 1 I/O registersDA2 DA1 DA0 Data register X’1F0’ Command block registersError register X’1F1’ UNC Idnf SET Multiple Mode Features register X’1F1’Sector Count register X’1F2’ Cylinder Low register X’1F4’ Sector Number register X’1F3’Cylinder High register X’1F5’ Status register X’1F7’ Device/Head register X’1F6’DEV HS3 HS2 HS1 HS0 BSY Interface Control block registers Command register X’1F7’Alternate Status register X’3F6’ Device Control register X’3F6’ Host CommandsCommand code and parameters HOB Srst Command Name Command code and parameters 1Parameter Used Command code and parameters 2 EXT Flush Cache EXT Host Commands Command descriptions Host Commands Recalibrate X’10’ to X’1F’ Read Sectors X’20’ or X’21’ MSB End head No. / LBA MSB Read Long X’22’ or X’23’ Write Sectors X’30’ or X’31’ 1F7 HST Status information 1F6 HDH Write Long X’32’ or X’33’ Write Verify X’3C’ Read Verify Sectors X’40’ or X’41’ Seek X’70’ to X’7F’ Execute Device Diagnostic X’90’ Diagnostic code Host Commands Initialize Device Parameters X’91’ Download Micro Code X’92’ Operation of Download Micro Code Standby Immediate X’94’ or X’E0’ Idle Immediate X’95’ or X’E1’ Standby X’96’ or X’E2’ Idle X’97’ or X’E3’ Host Commands Check Power Mode X’98’ or X’E5’ ’FF’ Sleep X’99’ or X’E6’ Smart X’B0 Features Register values subcommands and functions 1 Smart Disable Operations Features Register values subcommands and functions 2Smart Enable Operations Smart Read LOG Smart ENABLE/DISABLE Auto OFF-LINE Features Register values subcommands and functions 3’DA’ Smart Return Status Interface 1FF Format of device attribute value dataFormat of insurance failure threshold value data Data format version number Attribute ID Attribute value for the worst case so far Status FlagCurrent attribute value Raw attribute value Self-test execution status 10 Off-line data collection status11 Self-test execution status Failure prediction capability flag Off-line data collection capability12 Off-line data collection capability 13 Failure prediction capability flag Check sum Error logging capability14 Error logging capability Insurance failure threshold Smart error logging 16 Data format of Smart Summary Error Log Total number of drive errors Command data structureError data structure 17 Data format of Smart Comprehensive Error Log 1FC Smart Self-Test18 Smart self-test log data format Self-test number Current LBA under test 19 Selective self-test log data structureTest Span Current Span under test 20 Selective self-test feature flags Feature FlagsSelective Self-test pending time min Device Configuration Freeze Device Configuration XB1Device Configuration Restore Device Configuration Identify Device Configuration Identify FR = C2h Device Configuration Restore FR = C0hDevice Configuration Freeze Lock FR = C1h Device Configuration SET FR = C3h Host Commands 21 Device Configuration Identify data structure Execution example of Read Multiple command Read Multiple X’C4’ MSB Write Multiple X’C5’ Interface SET Multiple Mode X’C6’ Interface Read DMA X’C8’ or X’C9’ End head No. / LBA MSB Write DMA X’CA’ or X’CB’ Interface Read Buffer X’E4’ Flush Cache X’E7’ Write Buffer X’E8’ Identify Device X’EC’ Identify Device DMA X’EE’ 22 Information to be read by Identify Device command 1 ’3FFF’ 22 Information to be read by Identify Device command 2 Word Command without interrupt supports 2, 4, 8 and 16 sectors = Supports the Host Protected Area feature set = Supports the CFA Compact Flash Association feature set Interface Host Commands Diagnosis Word Bit Reserved Security level High, 1 Maximum ’AA’ SET Features X’EF’23 Features register values and settable modes ’BB’ Data Transfer Mode Advanced Power Management APM Automatic Acoustic Management AAM 24 Contents of Security SET Password data At command issuance I-O register contents 1F7 hCM 1F6 hDH When the user password is selected When the master password is selectedSecurity UNLOCKX’F2’ Host Commands Security Erase Prepare X’F3’ Security Erase Unit X’F4’ Security Freeze Lock X’F5’ At command issuance I-O register contents 1F7 hCM 1F6 hDH 26 Contents of security password Host Commands Read Native MAX Address X’F8’ SET MAX X’F9’ SET MAX Address SET MAX SET Password FR = 01h SET MAX Lock FR = 02h SET MAX Unlock FR = 03h SET MAX Freeze Lock FR = 04h Interface Read Sectors EXT X’24’ Option customizing Description Read DMA EXT X’25’ Option customizing Description HOB=0 Error reporting conditionsHOB=1 Read Multiple EXT X’29’ Option customizing Description Read LOG EXT X2F Optional command Customize Description Interface Write Sectors EXT X’34’ Option customizing Description Write DMA EXT X’35’ Option customizing Description SET MAX Address EXT X’37’ Option customizing Description SET MAX LBA Write Multiple EXT X’39’ Option customizing Description Write LOG EXT X’3F’ Optional command Customize Description Host Commands Read Verify Sectors EXT X’42 Option customizing Description Flush Cache EXT X’EA’ Option customizing Description Error posting 27 Command code and parameters 1 27 Command code and parameters 2 PIO Data transferring commands from device to host Command ProtocolExecute Device Diagnostic Initialize Device Parameters Read Sectors Command protocol Protocol for command abort PIO Data transferring commands from host to device Write Sectors command protocol Commands without data transfer Read Multiple EXT Write Multiple EXT Sleep Other commandsDMA data transfer commands Read DMA EXT Write DMA EXT Indentify Device DMA Normal DMA data transfer Ultra DMA Feature Set Overview Ultra DMA data in commands Phases of operationInitiating an Ultra DMA data in burst Pausing an Ultra DMA data in burst Data in transfer Terminating an Ultra DMA data in burst Interface Ultra DMA Feature Set Ultra DMA data out commands Initiating an Ultra DMA data out burst Pausing an Ultra DMA data out burst Data out transfer Terminating an Ultra DMA data out burst Ultra DMA Feature Set Ultra DMA CRC rules DIOR-HDMARDY-HSTROBE Series termination required for Ultra DMA28 Recommended series termination for Ultra DMA DIOW-STOP PIO data transfer TimingPIO data transfer timing 10 Multiword DMA data transfer timing mode Multiword data transfer Ultra DMA data transfer 11 Initiating an Ultra DMA data in burst Name Mode Comment Strobe 29 Ultra DMA data burst timing requirements 2 MIN MAX Mode Name Comment 30 Ultra DMA sender and recipient timing requirements DD150 at device Dstrobe at host Sustained Ultra DMA data in burstDstrobe at device DD150 at host Dmack Host pausing an Ultra DMA data in burstDmarq Stop Device terminating an Ultra DMA data in burst Host Host terminating an Ultra DMA data in burstDA0, DA1, DA2 CS0, CS1 16 Initiating an Ultra DMA data out burst Hstrobe at host DD150 at host Sustained Ultra DMA data out burstHstrobe at device DD150 at device Device DMACK- host Stop host DDMARDY- device Device pausing an Ultra DMA data out burstHstrobe host DD150 Host Host terminating an Ultra DMA data out burst 19 Host terminating an Ultra DMA data out burst Dmarq device DMACK- host Device terminating an Ultra DMA data out burstDD150 Host Master and slave devices are present 2-drives configuration Power-on and resetOnly master device is present This page is intentionally left blank Operations Device Response to the Reset Response to power-on Response to hardware reset Response to power-on Response to hardware reset Response to software reset Response to software reset Response to diagnostic command Response to diagnostic command Active mode Power SavePower save mode Active idle mode Standby mode Sleep mode Defect Processing Power commandsSpare area Sector slip processing Alternating processing for defective sectorsTrack slip processing Automatic alternating processing Automatic alternating processing 8MB buffer 8,388,608 bytes Read-ahead CacheData buffer structure Read Sectors EXT Read Multiple EXT Read DMA EXT Read Multiple EXT Read Dmaext Commands that are targets of cachingCaching operation Data that is a target of caching Operations Using the read segment buffer Miss-hit Sequential Hit Full hit Partial hit Cache operation Command that are targets of cachingWrite Cache Invalidation of cached data Cashing function when power supply is turned on Status report in the event of an errorReset response Enabling and disabling Write Cache This page is intentionally left blank Glossary PIO Programmed input-output Power save modeRotational delay Positioning Status VCM This page is intentionally left blank Acronyms and Abbreviations This page is intentionally left blank Index AAM Index Information to be read by Identify Read Sectors Command Read Native MAX Address Surface temperature measurement This page is intentionally left blank Comment Form Japan This page is intentionally left blank C141-E202-01EN This page is intentionally left blank