JP2792228B2 - Magnetic disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk drive, and more particularly, to a magnetic disk drive that operates based on a command from a host machine.

[Conventional technology]

In magnetic recording signal processing, a signal detection for generating a pulse corresponding to a peak position of an analog signal reproduced by a magnetic head and an encoding method for converting an information bit sequence to be recorded into a code to be recorded on an actual recording medium are used. Technology is important.

In digital magnetic recording, a clock signal for synchronization must be generated from a reproduction signal in addition to an information bit string for faithful reproduction. The NRZ code is a basic coding method that performs magnetization reversal only when information is "1",
With respect to the continuation of the information "0", no synchronization signal is obtained because there is no magnetization reversal. In recent high-density recording, modulation by the 1-7 encoding method is generally used so that the density of magnetization reversal is low to reduce the peak shift and the data discrimination window can be widened. This is because, as shown in FIGS. 4 and 5, the data to be recorded is changed to "1" by the contents of the current data bit to be encoded, the next data bit, and the immediately preceding 1-7 code data. The data is converted into another type of data so that the number of "0" between "1" is at least one and at the maximum is seven.

FIG. 6 shows a conventional example. The conventional example shown in FIG. 6 includes a code conversion circuit 20 for converting into 1-7 code bits 102,
Degoder circuit 40 for decoding 1-7 code bits 102 from code conversion circuit 20 using decoding start signal 101 as a trigger, and a clock correction signal from decoder circuit 40
A clock correction circuit 30 for correcting the basic clock 106 for reading by the 104 to generate the decoding clock 105, and a logical product of the RAW NRZ data 112 from the decoder circuit 40 and the decoding normal signal 113 to output NRZ data 111 And an AND gate 50.

When the decoding start signal 101 becomes active, decoding of the 1-7 code 102 from the code conversion circuit 20 is started by the decoder circuit 40. Here, when the clock correction signal 104 is output from the decoder circuit 40 to the clock correction circuit 30, the decoding clock 105 is transmitted from the clock correction circuit 30. Decoding is performed by the decoder circuit 40 in synchronization with the timing of the decoding clock 105. When the clock correction is performed normally and the decoding to “0000 ……” is confirmed, the decoding normal signal 113 becomes active and the RAW NR
The Z data 112 is transmitted to an upper circuit as NRZ data 111.

[Problems to be solved by the invention]

However, in the above conventional example, the read 1
When the -7 code bit data 102 is decoded, "0000", "0101", and "1111" are repeated as RAW NRZ data 112 depending on the decoding timing, as shown in FIG. Originally the decryption is expected here is "000
0 "pattern. The clock correction circuit 30 uses the clock correction signal 104 so that it can be decoded into a "0000" pattern.
Activate However, at this time, if a problem occurs in the clock correction circuit 30 or a fluctuation occurs in the basic clock 106, the decoding is not normally performed, the decoding normal signal 113 does not become active, and the NRZ data 111 ,
Only "0000" data is always transmitted. For this reason, there is a problem that not only data cannot be read out normally, but also the host device determines that there is no data in this area, a write operation is performed on this area, and data destruction occurs.

[Object of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages of the prior art, and in particular to a magnetic disk drive which prevents data destruction due to rewriting to the area even if decoding could not be performed correctly due to the inconvenience of a clock correction circuit or a decoding circuit. Is to provide.

[Means for solving the problem]

According to the present invention, a code conversion circuit for converting an analog signal read by a head into 1-7 code data, and converting the 1-7 code data into an NRZ (Non Return to Z
ero) In a magnetic disk drive having a decoder circuit for decoding into a signal and a clock correction circuit for correcting a frame of the decoded NRZ signal, writing and writing 1-7 code data from a code conversion circuit SYNC pattern detection means for knowing whether or not a SYNC pattern indicating the start of write data has been detected by the NRZ signal; and a 1-7 code signal input to a decoder circuit based on the output of the SYNC pattern detection means. And a SYNC pattern discriminating circuit for judging whether or not it is included and transmitting the result to the host machine. In addition, the SYNC pattern detecting means detects a GAP pattern detecting circuit for detecting that at least two "100" patterns have continued in the continuous 1-7 code data, and a write N
An encoding circuit for encoding the RZ data, and a logic "1" when the content of the SYNC byte indicating the beginning of the write data encoded by the encoding circuit is "0101" or "0111" in the NRZ data, A SYNC pattern detection circuit for outputting a pattern signal which becomes a logic "0" at times other than
The configuration includes two pattern detection circuits that are enabled by the value of the pattern signal output from the SYNC pattern detection circuit, and a logical sum gate for calculating the logical sum of the outputs of the two pattern detection circuits. . More specifically, the first pattern detection circuit includes 1-7 code data output from the code conversion circuit, the GAP pattern detected by the GAP pattern detection circuit, and the SYN
Based on the pattern signal output from the C pattern detection circuit, it is enabled when the pattern signal is "0", and the 1-7 code data following the GAP pattern is a SYNC byte corresponding to the pattern signal "0". Is output, a signal indicating that a SYNC pattern has been detected is output. The second pattern detection circuit includes 1-7 code data output from the code conversion circuit, the GAP pattern detected by the GAP pattern detection circuit, and the S
Based on the pattern signal output from the YNC pattern detection circuit, it is enabled when the pattern signal is "1", and the 1-7 code data following the GAP pattern is a SYNC byte corresponding to the pattern signal "1". Is output, a signal indicating that a SYNC pattern has been detected is output. This aims to achieve the above-mentioned object.

(Operation)

First, an analog signal read by the head is converted into 1-7 code data by a code conversion circuit. Next, it is determined by the SYNC pattern detecting means whether or not SYNC data is included in the 1-7 code data from the code conversion circuit and the data read by the write NRZ signal. When the SYNC pattern is detected, the SYNC detection signal from the SYNC pattern detection means becomes active. 1-
In the magnetic disk device having the 7-code conversion circuit, the SYNC pattern discriminating circuit is immediately activated, and if the SYNC detection signal from the SYNC pattern detecting means is active, it is determined that the data written in the area exists. Meanwhile, SY
If the NC detection signal is non-active, it is determined that there is no data written in the area, and is transmitted to the host device.

(Example of the invention)

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

In the embodiment shown in FIG. 1, a code conversion circuit 20 for converting to a 1-7 code bit 102 and a 1-7 code bit 10 from the code conversion circuit 20 triggered by a decoding start signal 101 are used as a trigger.
2, a clock correction circuit 30 for correcting the basic clock 106 for reading by the clock correction signal 104 from the decoder circuit 40 and extracting the decoded clock 105, and a RAW N from the decoder circuit 40.
Logical product of RZ data 112 and decode normal signal 113
AND gate 50 for outputting Z data 111, SYNC for knowing whether or not a SYNC pattern indicating the start of write data is detected by 1-7 code bits 102 from code conversion circuit 20 and write NRZ signal 108 And a pattern detecting means 1. Reference numeral 2 denotes a SYNC pattern determination circuit.

Here, the SYNC pattern detecting means 1 includes an encoding circuit 17 for encoding the write NRZ signal 108 using the encoding start signal 107 as a trigger, and a SYNC byte indicating the beginning of the write 1-7 data 114. "0101" or "0"
A SYNC pattern detection circuit 16 for outputting a pattern signal which becomes a logic "1" at the time of "110" and a logic "0" at other times, and a continuation from the code conversion circuit 20 triggered by the decoding start signal 101. A GAP pattern detection circuit 11 for detecting whether at least two "100" patterns have continued to the 1-7 code bits 102, a first pattern signal 109 from the SYNC pattern detection circuit 16, and a GAP pattern detection circuit A first pattern detection circuit 12 for detecting a pattern from the GAP pattern detection signal 103 from the code conversion circuit 11 and the 1-7 code bits 102 from the code conversion circuit 20;
An inverter gate 15 for performing logical negation of the first pattern signal 109 from the NC pattern detection circuit; a second pattern signal 110 from the inverter gate 15; a GAP pattern detection signal 103 from the GAP pattern detection circuit 11; A second pattern detection circuit 13 for detecting a pattern from the 1-7 code bits 102 from the conversion circuit 20, and an output of the first pattern detection circuit 12 and an output of the second pattern detection circuit 13 It comprises a logical sum gate 14 for taking a logical sum and outputting a SYNC detection signal 115.

Further, the magnetic disk device having the above-mentioned 1-7 code conversion circuit uses the output of the OR gate 14 to judge whether or not the read 1-7 code bit contains SYNC data, and judges the judgment result. Is transmitted to the host device.

 Next, the operation of this embodiment will be described.

(A) When the coding start signal 107 becomes active, the write NRZ signal 108 is written by the coding circuit 17 to write 1-7 data.
Encoded to 114. Then, the write 1-7 data 114 is transmitted to the SYNC pattern detection circuit 16.

(B) As shown in FIG. 2, when the NRZ signal of the upper 4 bits of the SYNC byte is converted into 1-7 code data, it is divided into three groups. In other words, when it is “001010”, “010101”, “010010”, or “010100”, the group A is “001000”
Is a group B, and "001001" is a group.
However, the group C is always integrated into the group A or B according to the contents of the following upper 4 bits.

(C) The SYNC pattern detection circuit 16 activates the first pattern signal 109 when the write 1-7 data 114 is in group A, and inactivates it when it is in group B.

(D) When the first pattern signal 109 is active, the first pattern detection circuit 12 is enabled, and when it is inactive, the second pattern detection circuit 13 is enabled.

(E) When the decoding start signal 101 becomes active, the 1-7 code 102 from the code conversion circuit 20 is
Starts decoding. Here, when the clock correction signal 104 is output from the decoder circuit 40 to the clock correction circuit 30, the decoded clock 105 is sent from the clock correction circuit 30. The decoding is performed by the decoder circuit 40 in synchronization with the timing of the decoding clock 105.

(F) When clock correction is normally performed and decoding to “0000...” Can be confirmed, the decode normal signal 113 becomes active, and the RAW NRZ data 112 is transmitted to the higher-level circuit as NRZ data 111.

(G) When the decoding start signal 101 becomes active, G
The 1-7 code 102 is transmitted to the AP pattern detection circuit 11.

(H) When the GAP pattern detection circuit 11 detects a GAP pattern that is continuous with "100100 ...", the GAP pattern detection signal 10
3 becomes active.

(I) When the SYNC pattern following the GAP pattern is the A group, it is detected by the first pattern detection circuit 12, and when it is the B group, it is detected by the second pattern detection circuit 13.

(J) When the SYNC pattern is detected, the SYNC detection signal 115 becomes active.

(K) A magnetic disk drive having the circuit of FIG.
If the NC detection signal 115 is active, it is considered that there is data written in the area.
If 5 is active, it is considered that there is no data written in the area, and the data is transmitted to the host device.

〔The invention's effect〕

As described above, according to the present invention, the SYNC pattern detecting means is provided,
Since a configuration is adopted in which a SYNC pattern determining circuit for judging whether or not data is included and transmitting the judgment result to a higher-level device is provided, the SYNC at the time of writing is
By latching the pattern, it is possible to recognize whether or not the data written in the area exists without decoding the read 1-7 code bits.
For this reason, it is possible to provide an unprecedented excellent magnetic disk device that prevents data destruction due to rewriting in the area even when decoding cannot be performed correctly due to a malfunction of the clock correction circuit or the decoding circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is an explanatory diagram showing a case where signals 00-0F are encoded into a 1-7 code, FIG. 3 is an explanatory diagram showing a case where a GAP pattern is decoded, and FIG. 4 and FIG. Fig. 6
FIG. 1 is a configuration diagram showing a conventional example. 1 SYNC pattern detecting means 2 SYNC pattern discriminating circuit 20 Code conversion circuit 30 Clock correction circuit 40 Decoder circuit

Claims (1)

(57) [Claims] 1. A code conversion circuit for converting an analog signal read by a head into 1-7 code data, and converting the 1-7 code data into an NRZ (Non Return to Zero)
o) In a magnetic disk drive having a decoder circuit for decoding into a signal and a clock correction circuit for correcting a frame of the decoded NRZ signal, 1-7 code data from the code conversion circuit SYNC pattern detection means for knowing whether or not a SYNC pattern indicating the start of write data is detected by the write NRZ signal; and a 1-7 code signal input to the decoder circuit based on the output of the SYNC pattern detection means. SY
A SYNC pattern discriminating circuit for judging whether or not NC data is included and transmitting the result to a higher-level device, wherein the SYNC pattern detecting means detects 1-7 code data output from the code conversion circuit. From the inside, a GAP pattern detection circuit for detecting a GAP pattern consisting of “100100”, an encoding circuit for encoding the write NRZ data, and a start of the write data encoded by the encoding circuit The content of the SYNC byte is NRZ data and is "0101" or "011".
A SYNC pattern detection circuit for outputting a pattern signal which becomes a logic "1" when it is "0" and a logic "0" otherwise, and 1-7 code data outputted from the code conversion circuit, Based on the GAP pattern detected by the pattern detection circuit and the pattern signal output from the SYNC pattern detection circuit, the pattern signal is enabled when the pattern signal is "0" and the 1-7 code data following the GAP pattern If a SYNC byte corresponding to the pattern signal “0” is matched, a first pattern detection circuit that outputs a “signal that detected a SYNC pattern”, and 1-7 code data output from the code conversion circuit, Based on the GAP pattern detected by the GAP pattern detection circuit and the pattern signal output from the SYNC pattern detection circuit, the pattern signal Is enabled when is "1", and outputs a "signal detected a SYNC pattern" if the 1-7 code data following the GAP pattern matches the SYNC byte corresponding to the pattern signal "1". A magnetic disk drive comprising: two pattern detection circuits; and a logical sum gate for obtaining a logical sum of outputs of the two pattern detection circuits.