Read-ahead Cache, Data buffer structure | Fujitsu MHT2060BH specification

6.4 Read-ahead Cache

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 6.5)

8MB buffer

8,192 KB (8,388,608 bytes)

For MPU work

For R/W command

336 KB

7,856 KB

(344,064 bytes)

(8,044,544 bytes)

Figure 6.5

Data buffer structure

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

•

•

•

•

READ SECTOR (s) (EXT)

READ MULTIPLE (EXT) READ DMA (EXT) READ FP DMA QUEUED

C141-E203-01EN

6-11

Image 237

Fujitsu MHT2060BH, MHT2040BH, MHT2080BH manual Read-ahead Cache, Data buffer structure, 8MB buffer

Contents

Disk Drives Product Manual MHT2080BH, MHT2060BH, MHT2040BH Handling of This Manual For Safe Operation Revision History This page is intentionally left blank Overview of Manual Preface Conventions for Alert Messages Operating EnvironmentConventions Liability Exception This page is intentionally left blank Important Alert Messages Important Alert Items This page is intentionally left blank MHT2040BH Disk Drives Maintenance Manual Manual OrganizationMHT2040BH Disk Drives Product Manual This page is intentionally left blank Contents Theory of Device Operation Installation Conditions Interface 102 Operations GL-1 Acronyms and Abbreviations AB-1IN-1 Figures Illustrations Response to power-on when the host is powered Tables Recommended connector specifications for the host system Relationship between combination of Identifier and Security Device Overview Features Functions and performanceAdaptability Interface Specifications summary Device SpecificationsSpecifications 1/2 MHT2080BH MHT2060BH MHT2040BH Model and product number Specifications 2/2MHT2080BH Examples of model names and product numbers Power Requirements Input VoltageRipple Current and power dissipation Current Requirements and Power Dissipation Current fluctuation Typ. at +5 V when power is turned on Environmental SpecificationsPower on/off sequence Environmental specifications Shock and vibration specification Acoustic noise specificationAcoustic Noise Shock and Vibration Data assurance in the event of power failure Service lifeReliability Mean time between failures Mtbf Unrecoverable read error Error RatePositioning error Media Defects Advanced Power Management Advanced power management Interface Power Management IPM Host-initiated Interface Power Management HipmDevice-initiated Interface Power Management Dipm Interface power management This page is intentionally left blank Device Configuration Device Configuration Sata interface System ConfigurationDrive connection Read/write circuit This page is intentionally left blank Installation Conditions Dimensions Dimensions Mounting Integration Guidance C141-E144Orientation Frame Limitation of mountingPCA Location of breather Ambient temperature Handling cautions Service area ESD Sumitomo 3MHios Connections with Host System Device connector Connector specifications for host system Signal segment and power supply segmentRecommended connector specifications for the host system Sata interface cable connection This page is intentionally left blank Theory of Device Operation Subassemblies OutlineDisk Spindle Air filter Circuit ConfigurationServo circuit Spindle motor driver circuit Power Supply Configuration PCA Power-on operation sequence Power-on Sequence Self-calibration Self-calibration contents Execution timing of self-calibration Command processing during self-calibration Read/write preamplifier PreAMP Read/write CircuitWrite circuit RLL code Meeprml Read circuit AGC circuitProgrammable filter circuit FIR circuit Digital PLL circuitD converter circuit Viterbi detection circuit Servo Control Servo control circuitMicroprocessor unit MPU Servo burst capture circuit Power amplifierA converter DAC Spindle motor control circuit Inner guard band IGB Data-surface servo formatData area Outer guard band OGB Physical sector servo configuration on disk surface Servo frame format Operation to move the head to the reference cylinder Actuator motor controlSeek operation Track-following operation Start mode Acceleration modeSpindle motor control Stable rotation mode This page is intentionally left blank Interface Physical Interface Interface signals Comreset / Cominit Comwake5VDC/GND Out of band signaling Signal interface regulation Primitives descriptions Physical Layer Electrical Requirements 1/2 Electrical specifications COMRESET/C Physical Layer Electrical Requirements 2/2Ominit Connector pinouts Connector pinouts Logical Interface Conceptual diagram of communication layers Physical layer Communication layersLink layer Transport layer Shadow Block Register Outline of the Shadow Block Register FIS types Outline of the frame information structure FISRegister Host to Device Register Host to Device FIS layout DMA Active Device to Host Register Device to Host TAG DMA Setup Device to Host or Host to Device Bidirectional Bist combinations Bist Active Bidirectional Data FIS Bidirectional layout Data Host to Device or Device to Host Bidirectional Error Field Shadow block registersUNC Sector Count Field exp Features Field expSector Number Field exp Cylinder Low Field exp Device/Head Field Cylinder High Field expHS3 HS2 HS1 HS0 HS3 Bit Error ERR bit Bit Device Write Fault DF bitStatus field Bit 7 Busy BSY bit Bit 2 Software Reset Srst Command FieldDevice Control Field EStatus Field Host Commands Command code and parametersCommand code and parameters 1/3 Command code and parameters 2/3 Command code and parameters 3/3 Command descriptions Recalibrate X’10’ to X’1F’ Error reporting conditions Read Sectors X’20’ or X’21’ LBA LBA LSB Read Long X’22’ or X’23’ Write Sectors X’30’ or X’31’ 00 *1 Error information Write Long X’32’ or X’33’ Cylinder No. LSB Write Verify X’3C’ Host Commands Read Verify Sectors X’40’ or X’41’ Host Commands Seek X’70’ to X’7F’ Diagnostic code Execute Device Diagnostic X’90’ Initialize Device Parameters X’91’ Operation of Download Microcode Download Microcode X’92’ Error reporting conditions 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 ’FF’ Check Power Mode X’98’ or X’E5’ Sleep X’99’ or X’E6’ Comreset Smart X’B0’ Features Field values subcommands and functions 1/3 Smart Enable Operations Features Field values subcommands and functions 2/3Smart Disable Operations Smart Read LOG Features Field values subcommands and functions 3/3 ’DB’ Smart ENABLE/DISABLE Auto OFF-LINESmart Return Status Key C2h 11 Format of guarantee failure threshold value data 10 Format of device attribute value data1FF Attribute ID Data format version number Current attribute value Status FlagAttribute value for the worst case so far Raw attribute value 12 Off-line data collection status Self-test execution status13 Self-test execution status 16 Drive error logging capability 14 Off-line data collection capability15 Failure prediction capability flag Smart error logging Guarantee failure thresholdChecksum 17 Log Directory Data Format 18 Data format of Smart Summary Error Log 1/2 Command data structure 18 Data format of Smart Summary Error Log 2/2Error data structure Total number of drive errors Smart Self-Test 19 Data format of Smart Comprehensive Error Log 1FC 20 Smart self-test log data formatSelf-test number Self-test index 21 Selective self-test log data structure Test SpanCurrent LBA under test 22 Selective self-test feature flags Feature FlagsCurrent Span under test Selective Self-test pending time min Device Configuration Restore Device Configuration XB1Device Configuration Freeze Device Configuration Identify Device Configuration Freeze Lock Features Field = C1h Device Configuration Restore Features Field = C0h Device Configuration SET Features Field = C3h Device Configuration Identify Features Field = C2h Word Value Content 23 Device Configuration Identify data structure Read Multiple X’C4’ Execution example of Read Multiple command LBA LSB Write Multiple X’C5’ At command issuance Shadow Block Registers setting contents SET Multiple Mode X’C6’ Host Commands Read DMA X’C8’ or X’C9’ LBA Write DMA X’CA’ or X’CB’ Host Commands Read Buffer X’E4’ Flush Cache X’E7’ Write Buffer X’E8’ Identify Device X’EC’ Identify Device DMA X’EE’ ’3FFF’ 24 Information to be read by Identify Device command 1/3 24 Information to be read by Identify Device command 2/3 24 Information to be read by Identify Device command 3/3 Interface Bit 0 Reserved C141-E203-01EN FIS Host Commands Word Bit Bit 0 1 = Supports the Mode C141-E203-01EN Interface 25 Features field values and settable modes 1/2 SET Features X’EF’ 25 Features field values and settable modes 2/2 Data Transfer Mode Advanced Power Management APM Automatic Acoustic Management AAM Serial ATA Functions 26 Contents of Security SET Password data Error reporting conditions When the master password is selected When the user password is selectedSecurity UNLOCKX’F2’ Host Commands Security Erase Prepare X’F3’ Security Erase Unit X’F4’ Security Freeze Lock X’F5’ Error reporting conditions 28 Contents of security password Error reporting conditions Lbalsb Read Native MAX Address X’F8’ SET MAX Address SET MAX X’F9’ SET MAX SET Password Features Field = 01h Password information SET MAX Lock Features Field = 02h SET MAX Unlock Features Field = 03h SET MAX Freeze Lock Features Field = 04h Read Sector S EXT X’24’ Description CL EXPSN EXP Read DMA EXT X’25’ Description Read Native MAX Address EXT X’27’ Read Multiple EXT X’29’ Read LOG EXT X2F CL EXP SN EXP 30 Tag field information 29 Data format of Read Log Ext log page 10h Write Sector S EXT X’34’ Description Write DMA EXT X’35’ Description SET MAX Address EXT X’37’ SET MAX LBA Write Multiple EXT X’39’ Write LOG EXT X3F Error information 132 C141-E203-01EN Read Verify Sector S EXT X’42’ Flush Cache EXT X’EA’ Write Multiple FUA EXT XCE Write DMA FUA EXT X3D Read FP DMA Queued Write FP DMA Queued 31 Command code and parameters 1/2 Error postingCommand Name Sfrw Sfrr 31 Command code and parameters 2/2 Command Protocol Non-data command protocolExecute Device Diagnostic Initialize Device Parameters Host PIO data-in command protocol Piosu Data PIO data-out command protocol Piosu 12 PIO data-out command protocol Read DMA EXT Identfy DMA DMA data-in command protocol Write DMA EXT FUA EXT DMA data-out command protocol Read FP DMA Queued Write FP DMA Queued Native Command Queuing protocol 15 Read FP DMA Queued command protocol 16 Write FP DMA Queued command protocol 17 Power-on sequence Power-on and Comreset 18 Comreset sequence Operations Response to power-on Reset and Diagnosis Reset and Diagnosis Response to Comreset Response to Comreset Response to a software reset Response to a software reset Power save mode Power SaveActive mode Active idle mode Sleep mode Standby mode Power commands Interface Power Save Power save mode of the interfacePartial mode Slumber mode Read-ahead Cache Data buffer structure8MB buffer Commands that are targets of caching Caching operationData that is a target of caching Invalidating caching-target data Miss-hit Using the read segment buffer Full hit Sequential hit HAP end location of the previous read command Partial hit Write Cache Command that are targets of cachingCache operation Invalidation of cached data Comreset and software reset response Status report in the event of an errorCashing function when power supply is turned on Enabling and disabling This page is intentionally left blank Glossary Rotational delay Power save modePIO Programmed input-output Positioning Acronyms and Abbreviations This page is intentionally left blank Index Block diagram Index Device-initiated interface power Frame information structure FIS Moving head to reference cylinder .4-13 RLL algorithm run length limited Read Native MAX Address Sensing and compensating for IN-8 C141-E203-01EN Comment Form Disk Drives Product ManualJapan This page is intentionally left blank C141-E203-01EN This page is intentionally left blank