CN105976839A - 通过缓存不同径向偏移处的信号样本执行重试操作的数据存储设备 - Google Patents

通过缓存不同径向偏移处的信号样本执行重试操作的数据存储设备 Download PDF

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CN105976839A
CN105976839A CN201610139253.6A CN201610139253A CN105976839A CN 105976839 A CN105976839 A CN 105976839A CN 201610139253 A CN201610139253 A CN 201610139253A CN 105976839 A CN105976839 A CN 105976839A
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T·S·陈
T·H·班
D·E·伯顿
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Western Digital Technologies Inc
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B19/00—Driving, starting, stopping record carriers not specifically of filamentary or web form, or of supports therefor; Control thereof; Control of operating function ; Driving both disc and head
    • G11B19/02—Control of operating function, e.g. switching from recording to reproducing
    • G11B19/04—Arrangements for preventing, inhibiting, or warning against double recording on the same blank or against other recording or reproducing malfunctions
    • G11B19/041—Detection or prevention of read or write errors
    • G11B19/044—Detection or prevention of read or write errors by using a data buffer
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59627—Aligning for runout, eccentricity or offset compensation
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10009—Improvement or modification of read or write signals
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10009—Improvement or modification of read or write signals
    • G11B20/10268—Improvement or modification of read or write signals bit detection or demodulation methods
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/10009—Improvement or modification of read or write signals
    • G11B20/10305—Improvement or modification of read or write signals signal quality assessment
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
    • G11B5/58—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B5/596—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on disks
    • G11B5/59688—Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns

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  • Signal Processing For Digital Recording And Reproducing (AREA)

Abstract

本申请涉及通过缓存不同径向偏移处的信号样本执行重试操作的数据存储设备。本申请公开一种数据存储设备，其包括在磁盘上方被致动的磁头。将磁头定位在磁盘上方的第一径向位置处，并且读磁盘上的码字的至少一部分以生成第一信号样本。生成第一信号样本的第一质量度量。将磁头定位在磁盘上方与第一径向位置不同的第二径向位置处，并且读取码字的至少一部分以生成第二信号样本。生成第二信号样本的第二质量度量。基于第一质量度量和第二质量度量，将第一信号样本的第一子集与第二信号样本的第二子集组合，以生成信号样本组合集。基于信号样本组合集，尝试对码字进行解码。

Description

通过缓存不同径向偏移处的信号样本执行重试操作的数据存 储设备
相关申请的交叉参考
本申请要求2015年3月13日提交的临时美国专利申请序列NO.62/133,105(代理卷号(Atty.Docket No.)T8117.P)的优先权，其全部公开内容通过引用并入在此。
背景技术
数据存储设备诸如磁盘驱动器包括磁盘和磁头，所述磁头连接到致动器臂远端，所述致动器臂通过音圈马达(VCM)围绕枢轴旋转以将所述磁头径向定位在所述磁盘上方。磁盘包括用于记录用户数据扇区和伺服扇区的多个径向间隔开的同心磁道。伺服扇区包括磁头定位信息(例如，磁道地址)，该磁头定位信息由磁头读取并且由伺服控制系统处理以当致动器臂从磁道到磁道寻址时控制该致动器臂。
图1示出作为包括由围绕每个伺服磁道的圆周记录的伺服扇区60-6N限定的若干伺服磁道4的现有技术磁盘格式2。每个伺服扇区6i包括用于存储周期模式的前导码(preamble)8，其允许读取信号的适当的增益调节和定时同步；以及用于存储用来将符号同步到伺服数据字段12的特殊模式的同步标记10。伺服数据字段12存储用来在寻道操作期间将磁头定位在目标数据磁道上方的粗略的磁头定位信息，诸如伺服磁道地址。每个伺服扇区6i还包括伺服脉冲串组14(servo bursts)(例如，N个伺服脉冲串和Q个伺服脉冲串)，该伺服脉冲串组14相对于彼此并相对于伺服磁道中心线以预定的相位来记录。基于相位的伺服脉冲串14提供精细的磁头位置信息，用于在写/读操作期间进行中心线跟踪的同时访问数据磁道。通过读取伺服脉冲串14，位置误差信号(PES)被生成，其中PES代表相对于目标伺服磁道的中心线测量的磁头的位置。伺服控制器处理PES以生成控制信号，该控制信号被应用于磁头致动器(例如，音圈马达)，以便在减少PES的方向上在磁盘上方径向致动磁头。
附图说明
图1是现有技术磁盘格式，其包括由伺服扇区限定的多个伺服磁道。
图2A是根据包括在磁盘上方被致动的磁头的一个实施例的磁盘驱动器形式的数据存储装置。
图2B是根据一个实施例的流程图，其中在多个径向位置处读取码字，并且产生的信号样本被合并以对码字解码。
图3A图示说明一个实施例，其中码字远离磁道被写入，导致在从单个径向位置读取时难以解码。
图3B图示说明当在不同的径向位置处读取时在码字的信号样本上生成的质量度量。
图4A-图4D图示说明一个实施例，其中在多个径向位置处读取码字，并且在每个径向位置处的最佳信号样本子集被用于对码字解码。
图5A根据一个实施例示出控制电路，其中基于格状序列检测器的分支度量生成质量度量。
图5B和图5C根据一个实施例图示说明格状序列检测器的操作。
具体实施方式
图2A示出根据包括在磁盘18上方被致动的磁头16的实施例的磁盘驱动器形式的数据存储装置。磁盘驱动器还包括被配置以用于执行图2B的流程图的控制电路20，其中磁头被定位在磁盘上方的第一径向位置处，并且读取磁盘上的码字的至少一部分以生成第一信号样本(方框22)。生成第一信号样本的第一质量度量(方框24)。磁头被定位在磁盘上方与第一径向位置不同的第二径向位置处，并且读取码字的至少一部分以生成第二信号样本(方框26)。生成第二信号样本的第二质量度量(方框28)。基于第一质量度量和第二质量度量，将第一信号样本的第一子集与第二信号样本的第二子集组合，以生成信号样本组合集(方框30)。基于信号样本组合集，尝试对码字进行解码(方框32)。
在图2A的实施例中，磁盘18包括限定多个伺服磁道36的多个伺服扇区340-34N，其中相对于伺服磁道以相同或不同的径向密度限定数据磁道。控制电路20处理从磁头16发出的读取信号38以解调伺服扇区340-34N并且生成代表磁头的实际位置和相对于目标磁道的目标位置之间的误差的位置误差信号(PES)。控制电路20中的伺服控制系统使用合适的补偿滤波器对PES滤波以生成应用于音圈马达(VCM)42的控制信号40，该音圈马达围绕枢轴旋转致动器臂44，从而在在磁盘18上方以减少PES的方向径向致动磁头16。伺服扇区340-34N可以包括任何合适的磁头位置信息，诸如用于粗略定位的磁道地址和用于精细定位的伺服脉冲串。伺服脉冲串可以包括任何合适的模式，诸如基于振幅的伺服模式或基于相位的伺服模式(图1)。
在一个实施例中，在写入操作期间，控制电路20将写入数据编码到被写入到磁盘18上的数据磁道的码字中。可以采用任何合适的编码技术，诸如合适的分组码(例如，里德-所罗门(Reed-Solomon))或迭代码(例如，低密度奇偶校验(LDPC))。当码字正被写入到磁盘18时，例如，由于振动影响磁盘驱动器，因此磁头16可能偏离数据磁道的中心线。因此，码字的至少一部分可能远离磁道太远被写入以至于在单个旋转读取操作(即，通过在单个径向位置处读取码字)期间不能使码字被成功地解码。图3A示出被写入到数据磁道的示例码字，其中码字包括多个区段(segment)(在该示例中为14个区段)，其中每个区段包括任何合适的大小(例如，单个比特、字节，或若干字节)。在图3A的示例中，振动影响磁盘驱动器使得磁头偏离数据磁道，从而造成第一五个区段逐渐更远离中心线被写入。最终，控制电路可以中止当前的写入操作(在当前的磁盘旋转期间)，并且然后，稍后在振动消失之后，完成码字的剩余区段的写入。当尝试读取图3A中所示的码字时，控制电路可以最初读取数据磁道的中心线，并且尝试对码字进行解码。然而，在第一五个区段中的一个或多个上生成的信号样本可能质量太差，以至于不能使码字被成功解码。
当码字不可通过读取数据磁道的中心线来恢复时，现有技术已经尝试通过在某一径向偏移处重新读取数据磁道来恢复码字。参考图3A的示例，现有技术可以尝试通过朝向码字的顶部的径向偏移来重读取码字，使得在整个码字上生成的信号样本的平均质量提高，由此增加成功解码的机会。然而，在一些情况下，即使当磁头被定位在最佳径向位置处时，信号样本的平均质量可能仍然还不足以使码字可恢复。
图3B图示说明当磁头相对于数据磁道的中心线被定位在不同的径向位置处时针对图3A中所示的码字的每个区段(即，针对对应于码字的每个区段的(一个或多个)信号样本)生成的质量度量。在该示例中，质量度量的较低数字对应于较好的质量(质量度量255代表最坏的质量)。在该示例中，当以+5的偏移，或者可能的话，以+10的偏移读取码字时，可以生成最佳平均质量度量，但如果以这些偏移中的任一者读取(即，使用以单个径向偏移读取的所有的信号样本)，则码字可能仍然是不可恢复的。因此，在一个实施例中，在多个径向位置处读取码字，并且基于产生的质量度量合并在每个径向位置处产生的信号样本的子集。信号样本的组合集可以具有足够高的质量，使得能够成功地对码字进行解码。
图4A-图4D图示说明示例实施例，在该示例实施例中，通过在不同的径向位置处读取码字来逐渐更新代表图3A中所示的码字的每个区段的(一个或多个)信号样本，直到信号样本组合集允许码字的成功解码。图4A示出当磁头被定位在数据磁道的中心线上方时在码字的每个区段上生成的质量度量。对应于第一五个区段的质量度量可能太差以至于不能成功解码，所以磁头被定位在+5的径向偏移处以重新读取码字，如图4B所示。在每个区段上生成的所得质量度量与在图4A中生成的质量度量相比较。对应于较好的可比性的质量度量的(一个或多个)信号样本被用于替换先前生成的对应的信号样本。这由图4B中所示的被重点突出的区段图示说明，其中对应于区段1-区段5和区段8的(一个或多个)信号样本替换在先前的读取操作期间生成的信号样本。然后基于信号样本组合集第二次尝试对码字进行解码。如果码字仍然不可恢复，则通过在+10的径向偏移处重新读取码字来重复该过程，如图4C所示。对应于较好的质量度量的信号样本替换先前存储的信号样本，并且进行另一次尝试以恢复码字。如果码字仍然不可恢复，则通过在+15的径向偏移处重新读取码字来重复该过程，如图4D所示。对应于较好的质量度量的信号样本替换先前存储的信号样本，并且进行另一次尝试以恢复码字。最终，信号样本组合集可以达到足够高的质量以实现码字的成功解码。
在一个实施例中，在重新读取操作期间，控制电路可以以远离数据磁道的中心线的任意方向调整磁头的径向偏移。然后，控制电路可以评估信号样本的质量度量以确定质量度量是否改善。如果质量度量劣化，则控制电路可以在继续迭代之前反转径向偏移的方向。参考图4A-图4D的示例，控制电路最初可以朝向远离数据磁道的中心线的负方向(例如，在-5的径向偏移处开始)偏移磁头。如图3B所示，产生的质量度量将变得比先前生成的质量度量更差，并且因此在继续进行之前，控制电路可以反转偏移的方向。
在一个实施例中，控制电路可以通过用正偏移和负偏移两者读取码字来生成信号样本组合集。参考图3B的示例，控制电路可以首先用-5的偏移读取码字，并且然后替换对应于区段9、区段11和区段14的(一个或多个)信号样本，这是由于质量度量将从40改善到20。然后，控制电路可以在-10的偏移处读取码字以确定质量度量对于任何区段没有改善。然后，控制电路可以反转偏移的方向以更新信号样本组合集，如以上参考图4A-图4D所述。
当从磁盘读取码字时，控制电路可以生成任何合适的度量。图5A根据实施例示出控制电路，其中读取信号38被采样以生成信号样本46。信号样本46用均衡器滤波器48滤波，例如，均衡器滤波器48可以操作以将记录通道的传递函数构造为合适的部分响应(PR)记录通道(例如，PR4记录通道)。对应于码字的均衡化信号样本50被存储在样本缓存器52中并且由合适的格状序列检测器54(例如，维特比序列检测器)进行处理。在一个实施例中，格状序列检测器54可以提供有关记录的数据的初步判决，以便于定时恢复和增益控制。在一个实施例中，格状序列检测器54也可以生成质量度量56，诸如图3B所示。
在码字的初始读取期间(例如，在数据磁道中心线处)，存储在样本缓存器52中的均衡化信号样本50可以由合适的迭代解码器58(诸如LDPC解码器)处理，或者在另一个实施例中，其可以由与LDPC解码器结合的软输出维特比算法(SOVA)检测器处理。如果解码失败，则控制电路在径向偏移处重新读取码字，并且格状序列检测器54生成信号样本的质量度量56。在方框58处，如上所述，当对应的质量度量优于(exceed)先前生成的质量度量时，控制电路替换样本缓存器52中的信号样本。存储在样本缓存器52中的信号样本的更新的组合集再次由迭代解码器58处理，并且该过程重复直到码字是可恢复的(或被视为不可恢复)。
图5B示出与PR4目标1-D2匹配的格状序列检测器的状态转换图。连接在图5B的PR4状态转换图中的状态的分支以y/x标记，其中y代表记录的二进制数据(NRZ编码的)，并且x代表对应的期望的信号样本。图5C示出对应于PR4状态转换图的网格，其中在任何给定的状态下，给定先前的均衡化信号样本的序列，计算代表下一个记录的比特是“0”或“1”的可能性的分支度量(例如，欧几里得度量(Euclidean metric))。当读取信号中的比特被评估时，数个幸存者序列(survivor sequence)被跟踪通过对应的网格，其最终基于每个幸存者序列的积累的分支度量被合并成最有可能的数据序列。
在一个实施例中，针对记录的序列的每个比特生成的分支度量可以代表图3B的实施例中的质量度量，使得在不同的径向偏移处读取码字之后，存储的信号样本的序列以比特分辨率被更新。在另一个实施例中，为了降低计算内存、时间和复杂性，例如，可以通过对针对数个比特中的每个比特生成的分支度量求平均来针对数个比特或数个字节生成质量度量。即，图3B中所示的每个质量度量可以在包括数个比特或字节块的码字的区段上生成。在又一个实施例中，控制电路可以调整质量度量的分辨率，以便在大的(heroic)误差恢复程序期间增大校正能力。例如，控制电路可以最初在相对大的字节块上生成每个质量度量。如果上述误差恢复程序不能恢复码字，则控制电路可以在增大质量度量的分辨率之后重新执行恢复程序(即，通过在更少数量的字节或比特上生成每个质量度量)。
再次参考图5A，在一个实施例中，格状序列检测器54可以诸如通过SOVA检测器生成记录的序列的每个比特的软判决。由格状检测器54输出的软判决可以被存储在样本缓存器52中，并且由迭代解码器56处理。在该实施例中，当在不同的径向位置处读取码字时，图3B所示的质量度量可以被用于更新样本缓存器52中的软判决。换句话说，短语“信号样本”在一个实施例中可能意味着读取信号的实际信号样本(或均衡化信号样本)，而在另一个实施例中，该术语可能意味着可以由格状检测器54、迭代解码器56或任何其他合适的软判决检测器/解码器生成的软判决(包括对数似然比)。
可以采用任何合适的控制电路来实施上述实施例中的流程图，诸如任何合适的集成电路或电路。例如，控制电路可以被实施在读取通道集成电路内或者在与读取通道分开的部件(例如，磁盘控制器)中，或者上述某些操作可以由读取通道执行并且其他操作由磁盘控制器执行。在一个实施例中，读取通道和磁盘控制器被实施为独立的集成电路，并且在可替换的实施例中，它们被制造到单个集成电路或片上系统(SOC)中。另外，控制电路可以包括被实施为独立的集成电路、被集成到读取通道或磁盘控制器电路中或被集成到SOC中的合适的前置放大器电路。
在一个实施例中，控制电路包括执行指令的微处理器，该指令可操作以使得微处理器执行本文所描述的流程图。该指令可以被存储在任何计算机可读介质中。在一个实施例中，它们可以被存储在微处理器外部的非易失性半导体存储器上或与微处理器一起集成在SOC中。在另一个实施例中，指令被存储在磁盘上，并且在磁盘驱动器上电时被读取到易失性半导体存储器中。在又一个实施例中，控制电路包括合适的逻辑电路，诸如状态机电路。
在各种实施例中，磁盘驱动器可以包括磁性磁盘驱动器、光盘驱动器等。另外，虽然上面的示例涉及磁盘驱动器，但各种实施例并不局限于磁盘驱动器，并且可以被应用于其他数据存储装置和系统，诸如磁带驱动器、固态驱动器、混合驱动器等。另外，一些实施例可以包括诸如计算设备、数据服务器设备、媒体内容存储设备等的电子设备，该电子设备包含如上所述的存储介质和/或控制电路。
以上描述的各种特征和过程可以彼此独立地使用，或可以按照各种方式被组合。全部可能的组合和子组合旨在落入本公开的范围内。另外，特定方法、事件或过程方框可以在一些实施方式中被省略。在本文中描述的方法和过程也不限于任何具体顺序，并且与其有关的方框或状态可以按照其他适合的顺序来执行。例如，所描述的任务或事件可以按照不同于具体公开的顺序的顺序执行，或多个可以被组合到单个方框或状态中。示例任务或事件可以顺序地、并行地或按照一些其他方式执行。任务或事件可以被添加到所公开的示例性实施例中或从其中去除。在本文中描述的示例系统和部件可以与所描述的不同地进行配置。例如，元件可以被添加到所公开的示例性实施例、从其中去除或与其相比被重新布置。
尽管描述了特定示例性实施例，这些实施例仅通过示例呈现，而不旨在限制在本文中公开的本发明的范围。因而，在以上的描述中不存在任何描述旨在暗含任何具体特征、特性、步骤、模块或块是必须的或不可缺少的。事实上，在本文中描述的新颖方法和系统可以以各种其它形式来体现；此外，可以对在本文中描述的方法和系统的形式进行各种省略、替代和修改而不脱离在本文中所公开的实施例的精神。

Claims (20)

1.一种数据存储设备，其包含：
磁盘；
在所述磁盘上方被致动的磁头；以及
控制电路，所述控制电路经配置以：
将所述磁头定位在所述磁盘上方的第一径向位置处，并且读取所述磁盘上的码字的至少一部分以生成第一信号样本；
生成所述第一信号样本的第一质量度量；
将所述磁头定位在所述磁盘上方不同于所述第一径向位置的第二径向位置处，并且读取所述码字的至少一部分以生成第二信号样本；
生成所述第二信号样本的第二质量度量；
基于所述第一质量度量和所述第二质量度量将所述第一信号样本的第一子集与所述第二信号样本的第二子集组合，以生成信号样本组合集；以及
基于信号样本的所述组合集，第一次尝试解码所述码字。
2.根据权利要求1所述的数据存储设备，其中当所述第二质量度量指示比所述第一质量度量更好的质量时，所述控制电路进一步经配置以使用对应于所述第二质量度量的所述第二信号样本的至少一部分生成所述信号样本组合集。
3.根据权利要求1所述的数据存储设备，其中所述控制电路进一步经配置以：
将所述磁头定位在所述磁盘上方不同于所述第一径向位置和所述第二径向位置的第三径向位置处，并且读取所述码字的至少一部分以生成第三信号样本；
生成所述第三信号样本的第三质量度量；
基于所述第三质量度量，使用所述第三信号样本来修改所述信号样本组合集；以及
基于修改的信号样本组合集，第二次尝试解码所述码字。
4.根据权利要求3所述的数据存储设备，其中当所述第三质量度量指示比所述第一质量度量和所述第二质量度量更好的质量时，所述控制电路进一步经配置以使用对应于所述第三质量度量的所述第三信号样本的至少一部分修改所述信号样本组合集。
5.根据权利要求1所述的数据存储设备，其中所述控制电路进一步经配置以：
在第一多个所述第一信号样本上生成所述第一质量度量；以及
在第二多个所述第二信号样本上生成所述第二质量度量。
6.根据权利要求5所述的数据存储设备，其中所述控制电路进一步经配置以：
基于所述第一信号样本中的一个和期望的信号样本之间的第一差值生成所述第一质量度量；以及
基于所述第二信号样本中的一个和期望的信号样本之间的第二差值生成所述第二质量度量。
7.根据权利要求6所述的数据存储设备，其中所述第一差值对应于格状序列检测器的分支度量。
8.根据权利要求7所述的数据存储设备，其中所述控制电路进一步经配置以基于多个分支度量生成所述第一质量度量，所述多个分支度量由所述格状序列检测器在多个所述第一信号样本上生成。
9.根据权利要求1所述的数据存储设备，其中所述控制电路进一步经配置以：
基于所述第一信号样本中的一个和期望的信号样本之间的第一差值生成所述第一质量度量；以及
基于所述第二信号样本中的一个和期望的信号样本之间的第二差值生成所述第二质量度量。
10.根据权利要求9所述的数据存储设备，其中所述第一差值对应于格状序列检测器的分支度量。
11.一种操作数据存储设备的方法，所述方法包括：
将磁头定位在磁盘上方的第一径向位置处，并且读取所述磁盘上的码字的至少一部分以生成第一信号样本；
生成所述第一信号样本的第一质量度量；
将所述磁头定位在所述磁盘上方不同于所述第一径向位置的第二径向位置处，并且读取所述码字的至少一部分以生成第二信号样本；
生成所述第二信号样本的第二质量度量；
基于所述第一质量度量和所述第二质量度量，将所述第一信号样本的第一子集与所述第二信号样本的第二子集组合，以生成信号样本组合集；以及
基于所述信号样本组合集，第一次尝试解码所述码字。
12.根据权利要求11所述的方法，其中当所述第二质量度量指示比所述第一质量度量更好的质量时，其进一步包括使用对应于所述第二质量度量的所述第二信号样本的至少一部分生成所述信号样本组合集。
13.根据权利要求11所述的方法，其进一步包括：
将所述磁头定位在所述磁盘上方不同于所述第一径向位置和所述第二径向位置的第三径向位置处，并且读取所述码字的至少一部分以生成第三信号样本；
生成所述第三信号样本的第三质量度量；
基于所述第三质量度量，使用所述第三信号样本修改所述信号样本组合集；以及
基于修改的信号样本组合集，第二次尝试解码所述码字。
14.根据权利要求13所述的方法，其中当所述第三质量度量指示比所述第一质量度量和所述第二质量度量更好的质量时，其进一步包括使用对应于所述第三质量度量的所述第三信号样本的至少一部分来修改所述信号样本组合集。
15.根据权利要求11所述的方法，其进一步包括：
在第一多个所述第一信号样本上生成所述第一质量度量；以及
在第二多个所述第二信号样本上生成所述第二质量度量。
16.根据权利要求15所述的方法，其进一步包括：
基于所述第一信号样本中的一个和期望的信号样本之间的第一差值生成所述第一质量度量；以及
基于所述第二信号样本中的一个和期望的信号样本之间的第二差值生成所述第二质量度量。
17.根据权利要求16所述的方法，其中所述第一差值对应于格状序列检测器的分支度量。
18.根据权利要求17所述的方法，其进一步包括基于多个分支度量生成所述第一质量度量，所述多个分支度量由所述格状序列检测器在多个所述第一信号样本上生成。
19.根据权利要求11所述的方法，其进一步包括：
基于所述第一信号样本中的一个和期望的信号样本之间的第一差值生成所述第一质量度量；以及
基于所述第二信号样本中的一个和期望的信号样本之间的第二差值生成所述第二质量度量。
20.根据权利要求19所述的方法，其中所述第一差值对应于格状序列检测器的分支度量。
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