Samsung M8 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 M8 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 M8 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 88i9322 (Rev2.0) DSP & Interface/Disk Controller.

The 88i9322 (Rev2.0) 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 88C9310 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.

Spinpoint M8 Product Manual REV 2.3

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Contents M8 Product Manual Page Table of Contents Servo System Read and Write Operations Read Fpdma Queued 60h Read Log Extended 2Fh Read Long 22h Table of Tables Manual Organization ScopeUser Definition Sata ReferenceDescription IntroductionKey Features Standards and Regulations Hardware RequirementsSpecifications SpecificationsSpecification Summary Spindle speed RPM RPM ClassPhysical Specifications Physical SpecificationsLogical Configurations Physical dimensionsPerformance Specifications Power Requirements Power consumptionPower consumption RatedEnvironmental Specifications Environmental Specifications15.0 Reliability Specifications Installation Space RequirementsUnpacking Instructions MountingMounting Dimensions OrientationClearance Mounting-Screw ClearanceSata Connectivity Cable ConnectorsVentilation Serial ATA Power ManagementHDD Power, Sata Interface, and Factory Jumper Connector Pin Locations on the Drive Pcba Drive Installation DC Power Connector and SATA-Bus Interface Cable ConnectionsDC Spindle Motor Assembly Head / Disk Assembly HDABase Casting Assembly Disk Drive OperationCoverAssembly Voice Coil Motor and Actuator Latch Assemblies Disk Stack AssemblyHead Stack Assembly Air Filtration SystemDisk Controller Digital Signal Process and Interface ControllerDrive Electronics DDR Host Interface Control Block Buffer Control BlockFrequency Synthesizer Disk Control BlockDisk Ldpc Control Block Time Base Generator Power ManagementRead/Write IC Automatic Gain ControlAnalog Anti-Aliasing Low Pass Filter Analog to Digital Converter ADC and FIRRead Channel Servo SystemRead and Write Operations Read Caching Firmware FeaturesWrite Channel Write Caching Multi-burst ECC Correction Defect ManagementAutomatic Defect Allocation SmartSata II Interface Sata TerminologySpinpoint M8 Product Manual REV Physical Interface Signal Summary Signal DescriptionsControl Block Register Descriptions When read When written2 I/O Register Address RegistersError Register Ex F1h Command Block Register DescriptionsFeatures Register and Feature Extended Register Ex F1h Device Control Register ex F6hCommand Register Ex F7h Device Register Ex F6hStatus Register Ex F7h Staggered Spin-up Disable Control Sata II Feature SETDevice Activity Signal Auto-Activate in DMA Setup FISPhy. Event Counters Software Settings Preservation Sata Power ManagementCommand Code Parameters ATA Command DescriptionsCommand Table Command Descriptions Check Power Mode E5hCommand Device Configuration Overlay B1hDevice Configuration Overlay Feature Register Values Download Micro Code 92hDevice Configuration Identify data structure Word Content Flush Cache E7h, EAh extended Execute Device Diagnostics 90hDiagnostic Codes Format Track 50hContent Description Identify Device information=the fields reported in word 88 are valid EXT =Media Card Pass Through command feature set supported Word Content Description WWNIdle Immediate E1h Automatic Standby Timer PeriodsIdle E3h Read Buffer E4h Initialize Device Parameters 91hNOP 00h Read DMA C8h, 25h extendedRead 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 Prepare F3h Security Disable Password F6hRecalibrate 10h Security Erase Unit F4hSecurity Set Password data content Security Set Password F1hSecurity Erase Unit Password Word Content Security Freeze Lock F5hSecurity Unlock F2h Set Features EFhIdentifier Level Command result Seek 7xh11 Set Features Register Definitions 12 Transfer Mode ValuesSet Max Address F9h, 37h extended Set Multiple Mode C6h13 Set Max Feature Register Values Sleep E6hSmart enable/disable attribute auto-save D2h 14 Smart Feature Registers ValuesSmart disable operations D9h Smart B0hSmart enable operations D8h Smart execute off-line immediate D4hSmart read data D0h 15 Device Smart Data StructureData Structure Revision Number Bit Name Description 16 Smart Attribute Status Flags17 Smart Attribute Data List 18 Off-line Data Collection Status ValuesSelf-test execution status byte 19 Self-test Execution Status ValuesSmart write log sector D6h Smart read log sector D5hSmart return status DAh Write DMA CAh, 35h extended Standby Immediate E0hWrite Buffer E8h Write Fpdma Queued 61hWrite Sectors 30h, 34h extended Write Multiple Command C5h, 39h extendedWrite Long 32h Spinpoint M8 Product Manual REV General Information MaintenanceMaintenance Precautions HDD handling guide -Please handle HDD by side surfaces Service and Repair HDD handling guide Prevent Shocks
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