摘要:
A filter for compensating discrete secondary pulse formations associated with a data stream of discrete main pulses produced from data read from magnetic media. The filter's impulse response comprises a center coefficient with side compensating coefficients for attenuating the secondary pulses when the input signal is convolved with the impulse response. The magnitude and delay of the compensation coefficients are programmable and are adaptively adjusted to optimize the impulse response for a given environment. In a traditional FIR embodiment, two delay lines are used to generate the two programmable delays between the center coefficient and side compensation coefficients. In the preferred embodiment, an IIR filter provides the two programmable delays using only one delay line thereby reducing the size and cost of the circuit. Also in the preferred embodiment, the data stream is interleaved into an even and odd data stream and processed in parallel by two filters in order to double the throughput. Further, the pre-cursor correcting portion of the filter can be disabled in order to avoid delaying the data stream while still canceling the post-cursor secondary pulses. The filter also comprises attenuation and adder means to match the coincident sample values in amplitude and add them to substantially eliminate the effect of the secondary pulses in the discrete data stream.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a desired partial response, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a discrete time sequence detector. The read channel further employs an error tolerant sync mark detector, as well as a sync mark recovery procedure for synchronizing to the data when the sync mark is destroyed by a defect.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, computes a DC offset in the sample values in real time, and subtracts the DC offset from the read signal. This attenuates the deleterious affect a DC offset has on the detection algorithm used to detect the recorded data, such as the Viterbi detection algorithm.
摘要:
The low-data-delay triple-coverage code for on-the-fly error correction apparatus allows on-the-fly error correction with fewer redundancy bytes than needed for a non-overlaid data redundancy structure thereby producing corrected data with a low data delay. The present apparatus divides a received block of data into a plurality of fixed size sub-blocks with the last sub-block size being smaller than or equal to the fixed sub-block size. Three predefined error correcting code generator polynomials are used to accumulate redundancy values for the sub-blocks. At the end of each sub-block one of the three pre-defined error correcting code generator polynomials will have accumulated a redundancy value across the present sub-block data and the previous two sub-blocks of data and redundancy. After the accumulated redundancy has been output as write data the predefined error correcting code generator polynomial is reset. Therefore, the redundancy information contained in each sub-block covers that sub-block's data in addition to the data and redundancy in the previous two sub-blocks.
摘要:
A synchronous read channel having a single chip integrated circuit digital portion which provides digital gain control, timing recovery, equalization, digital peak detection, sequence detection, RLL(1,7) encoding and decoding, error-tolerant synchronization and channel quality measurement is disclosed. The integrated circuit accommodates both center sampling and side sampling, and has a high degree of programmability of various pulse shaping and recovery parameters and the ability to provide decoded data using sequence detection or digital peak detection. These characteristics, together with the error-tolerant sync mark detection and the ability to recover data when the sync mark is obliterated, allow a wide variety of retry and recovery strategies to maximize the possibility of data recovery. Various embodiments, including an embodiment incorporating the analog functions as well as the primary digital functions of the read channel in a single integrated circuit, and preferred embodiments utilizing a reduced complexity, programmable modified Viterbi detector supporting a broad class of partial response channels are disclosed.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a desired partial response, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a discrete time sequence detector. The read channel employs a Data Randomizer which processes unencoded user data to insure that the channel bit patterns with worst-case pattern sensitivity occur no more frequently than would be expected from random user data. The Data Randomizer employs two linear feedback shift registers: one generates a 63-bit sequence which is EXLUSIVE-OR-ed against the MSB of each pair of data bits, the other generates a 127-bit sequence which is EXCLUSIVE-OR-ed against the LSB of each pair of data bits. The Data Randomizer does not affect error propagation. When the Data Randomizer is enabled, the probability of encountering any specific pattern of length n channel bits at a randomly selected location within encoded data is approximately 1/2.sup.n.
摘要翻译:公开了一种同步读通道,其从位于磁盘介质上的磁读头读取模拟读信号,根据所需的部分响应对采样值进行滤波,从滤波后的采样值中提取定时信息,并检测估计数据序列 使用离散时间序列检测器从滤波后的样本值。 读通道采用数据随机化器,其处理未编码的用户数据,以确保具有最坏情况模式灵敏度的信道位模式不会比从随机用户数据预期的更频繁地发生。 数据随机化器采用两个线性反馈移位寄存器:一个产生一个63位的序列,它与每对数据位的MSB相对而言是EXLUSIVE-OR-,另一个产生一个127位的序列,它是独占 每对数据位的LSB。 Data Randomizer不影响错误传播。 当启用数据随机器时,在编码数据内随机选择的位置遇到长度为n个通道位的任何特定模式的概率大约为+ E,fra 1/2 + EE n。
摘要:
A mixed analog and digital gain control circuit for controlling the amplitude of an analog input signal. The circuit has a variable gain amplifier that receives the signal from a read/write recording head preamplifier. The output of the variable gain amplifier is connected through a multiplexer and equalizer to an analog to digital converter for converting the analog signal to digital sample values at controlled sampling times. A gain control circuit receives the digital values and the output of a pulse detector indicating when a pulse has occurred. A gain error detector within the gain control circuit determines the amount of error in the amplitude of each detected pulse, and this error amount is filtered and sent through a digital to analog converter and then through an exponentiating circuit. The output of the exponentiating circuit is connected to a gain control input of the variable gain amplifier.
摘要:
A synchronous read channel having a single chip integrated circuit digital portion which provides digital gain control, timing recovery, equalization, digital peak detection, sequence detection, RLL(1,7) encoding and decoding, error-tolerant synchronization and channel quality measurement is disclosed. The integrated circuit accommodates both center sampling and side sampling, and has a high degree of programmability of various pulse shaping and recovery parameters and the ability to provide decoded data using sequence detection or digital peak detection. These characteristics, together with the error-tolerant sync mark detection and the ability to recover data when the sync mark is obliterated, allow a wide variety of retry and recovery strategies to maximize the possibility of data recovery. Various embodiments, including an embodiment incorporating the analog functions as well as the primary digital functions of the read channel in a single integrated circuit, and preferred embodiments utilizing a reduced complexity, programmable modified Viterbi detector supporting a broad class of partial response channels are disclosed.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a desired partial response, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a discrete time sequence detector. A Channel Quality circuit accumulates various signals generated by the read channel, such as sample errors, gain errors, timing errors, etc., for use in calibrating the read channel components and estimating the bit error rate.
摘要:
A synchronous read channel is disclosed which samples an analog read signal from a magnetic read head positioned over a magnetic disk medium, filters the sample values according to a partial response of the form (1-D)(1+D).sup.n where n>1, extracts timing information from the filtered sample values, and detects an estimated data sequence from the filtered sample values using a discrete time sequence detector.