Samsung M9T manual Servo System, Read and Write Operations, Read Channel

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5.3 Servo System

The Servo System controls the position of the read/write heads and holds them on track during read/write operations. The Servo System also compensates for MR write/read offsets and thermal offsets between heads on different surfaces and for vibration and shock applied to the drive.

The Spinpoint M9T hard disk drive is an Embedded Sector Servo System. Positioning information is radially located in evenly spaced servo sectors on each track.

Radial position information can be provided from these sectors for each data head. Because the drive incorporates multiple data zones and each zone has a different bit density, split data fields are necessary for optimal use of the non-servo area of the disk. The servo area remains phase-coherent across the surface of the disk, even though the disk has various data zones. The main advantage of the Embedded Sector Servo System is that it eliminates the problems of static and dynamic offsets between heads on different surfaces. The Spinpoint M9T hard disk drive Servo System is classified as a digital servo system because track-following and seek control, bias cancellation, and other typical tasks are done in a Digital Signal Processor (DSP).

The Servo system has three modes of operation: track-following mode, settle mode, and velocity control mode.

1.Track-following mode is used when heads are “on-track.” This is a position loop with an integrator in the compensation.

2.Settle mode is used for all accesses; head switches, short-track seeks and long-track seeks. Settle mode is a position loop with velocity damping. Settle mode does not use feed forward.

3.Velocity control mode is used for acceleration and deceleration of the actuator for seeking of two or more tracks. A seek operation of this length is accomplished with a velocity control loop. The drive’s ROM stores the velocity profile in a look-up table.

5.4Read and Write Operations

The following two sections describe the read and write channels.

5.4.1The Read Channel

The drive has one read/write head for each of the data surfaces. The signal path for the Read Channel starts at the read/write heads. When the magnetic flux transitions recorded on a disk pass under the head, they generate low- amplitude, differential output voltages. The read/write head transfers these signals to the flexible circuit’s amplifier, which amplifies the signal.

The flexible circuit transmits the pre-amplified signal from the HDA to the PCBA. The EPRML channel on the PCBA shapes, filters, detects, synchronizes, and decodes the data from the disk. The Read/Write IC then sends the resynchronized data output to the 88i1022 DSP & Interface/Disk Controller.

The 88i1022 Disk Controller manages the flow of data between the Data Synchronizer on the Read/Write IC and its AT Interface Controller. It also controls data access for the external RAM buffer. The ENDEC of 88C10010 decodes the LDPC with post-processor format to produce a serial bit stream. This NRZ (Non Return to Zero) serial data is converted to 12-bits.

The Sequencer module identifies the data as belonging to the target sector. After a full sector is read, the

88i1022 checks to see if the firmware needs to apply an ECC algorithm to the data. The Buffer Control section of the 88i1022 stores the data in the cache and transmits the data to the AT bus.

Spinpoint M9T Product Manual REV 1.0

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Contents M9T Product Manual Page Table of Contents Iii Read Fpdma Queued 60h Read Log Extended 2Fh Read Long 22h Table of Tables Manual Organization ScopeUser Definition Reference SataIntroduction DescriptionKey Features Hardware Requirements Standards and RegulationsSpecification Summary SpecificationsLogical Configurations Physical SpecificationsPerformance Specifications Rated Power consumptionPower consumption Power RequirementsRotational Shock Environmental SpecificationsEnvironmental Specifications Linear Shock 1/2 sine pulseReliability Specifications Space Requirements InstallationMounting Unpacking InstructionsOrientation Mounting DimensionsSata Connectivity Cable ConnectorsVentilation Computer mainboard or Serial ATA host adapter Management PowerHDD Power, Sata Interface, and Factory Jumper Connector SATA-Bus Interface ConnectorDC Power Connector and SATA-Bus Interface Cable Connections Drive InstallationDisk Drive Operation Head / Disk Assembly HDABase Casting Assembly DC Spindle Motor AssemblyExploded Mechanical View Air Filtration System Disk Stack AssemblyHead Stack Assembly Voice Coil Motor and Actuator Latch AssembliesDisk Controller Digital Signal Process and Interface ControllerDrive Electronics DDR Buffer Control Block Host Interface Control Block Frequency Synthesizer Disk Control Block Disk Ldpc Control Block Automatic Gain Control Power ManagementRead/Write IC Time Base GeneratorAnalog to Digital Converter ADC and FIR Analog Anti-Aliasing Low Pass FilterRead Channel Servo SystemRead and Write Operations Read Caching Firmware FeaturesWrite Channel Write Caching 6 APM Defect ManagementAutomatic Defect Allocation SmartSata Terminology Sata II InterfaceSpinpoint M9T Product Manual REV Signal Descriptions Physical Interface Signal SummaryRegisters When read When written2 I/O Register Address Control Block Register DescriptionsCommand Block Register Descriptions Device Register Ex F6h Command Register Ex F7hStatus Register Ex F7h Auto-Activate in DMA Setup FIS Sata II Feature SETDevice Activity Signal Staggered Spin-up Disable ControlPhy Event Counters Sata Power Management Software Settings PreservationCommand Code Parameters ATA Command DescriptionsCommand Table Smart Download Micro Code 92h Command DescriptionsCheck Power Mode E5h Device Configuration Overlay B1hDevice Configuration Identify data structure Word Content Format Track 50h Execute Device Diagnostics 90hDiagnostic Codes Flush Cache E7h, EAh extendedIdentify Device information Content Description=the fields reported in word 88 are valid EXT =Media Card Pass Through command feature set supported WWN Word Content DescriptionIdle Immediate E1h Automatic Standby Timer PeriodsIdle E3h Read DMA C8h, 25h extended Initialize Device Parameters 91hNOP 00h Read Buffer E4hRead Long 22h Read Multiple Command C4h, 29h extendedRead Log Extended 2Fh Read Verify Sectors 40h, 41h extended Read Native Max Address F8h, 27h extendedRead Sectors 20h, 24h extended Security Erase Unit F4h Security Disable Password F6hRecalibrate 10h Security Erase Prepare F3hSecurity Freeze Lock F5h Security Set Password F1hSecurity Erase Unit Password Word Content Security Set Password data contentSeek 7xh Set Features EFhSecurity Unlock F2h 12 Transfer Mode Values 11 Set Features Register DefinitionsSleep E6h Set Multiple Mode C6h13 Set Max Feature Register Values Set Max Address F9h, 37h extendedSmart B0h 14 Smart Feature Registers ValuesSmart disable operations D9h Smart enable/disable attribute auto-save D2hSmart execute off-line immediate D4h Smart enable operations D8h15 Device Smart Data Structure Smart read data D0hByte 16 Smart Attribute Status Flags Bit Name Description18 Off-line Data Collection Status Values 17 Smart Attribute Data List19 Self-test Execution Status Values Self-test execution status byteSmart write log sector D6h Smart read log sector D5hSmart return status DAh Write Fpdma Queued 61h Standby Immediate E0hWrite Buffer E8h Write DMA CAh, 35h extendedWrite Sectors 30h, 34h extended Write Multiple Command C5h, 39h extendedSpinpoint M9T Product Manual REV General Information MaintenanceMaintenance Precautions HDD handling guide -Please handle HDD by side surfaces HDD handling guide Prevent Shocks Service and Repair
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