JPH01320681A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To prevent the writing of an erroneous signal by checking the presence and absence of the gap pattern and the synchronizing pattern of an encoded serial writing signal. CONSTITUTION:When a WRT signal (e) becomes '1,' and starts a writing action, a pattern decoder 4, first, detects a GAP pattern. For this reason, a detecting signal (f) becomes '1,' and this is held at a memory circuit 5. Continuously, since the decoder 4 detects an SYNC byte, a detecting signal (g) becomes '1.' Since an output (h) of the memory circuit 5 also maintains '1,' an output (i) of an AND gate 6 becomes '1,' and this is stored into a memory circuit 7. When a checking signal (l) becomes '1' at the writing period of the data part, since an output (k) of a NAND gate 8 becomes '0,' '0' is latched at a D type FF9 and an error output (m) becomes the condition of '0'. Thus, the writing to prevent the writing of a different signal can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk drive, and more particularly to means for detecting abnormalities in encoded signals written on a disk.

[Prior Art] A data writing format in a magnetic disk device is generally composed of a gap pattern (GAP), a synchronous byte pattern (SYNC), and a data pattern (DATA). FIG. 4 shows the write timing of each of these patterns. That is, GAP, 5YNC, DATA
Each pattern is generated by serially converting parallel data and then encoding it, and the write signal (WR
GAP, 5YNC, and DATA are sequentially written to the disk in synchronization with T). Each pattern of 5YNC and DATA is normally sent from the host device, but due to the difference in the interface with the host device, GAP can be sent from the host device or generated inside the magnetic disk device. There is a street.

[Problems to be Solved by the Invention] However, in the conventional magnetic disk device, when writing the above-mentioned encoded signal, GAP, 5YNC, DAT
There is no distinction between the patterns of
Even if some abnormality occurs, such as when a byte is not sent, the write operation continues, resulting in the problem of writing an erroneous signal.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a magnetic disk device that can detect an abnormal signal when writing an encoded signal and prevent writing of an erroneous signal.

[Means for Solving the Problems] A magnetic disk device according to the present invention includes a detection circuit that detects a gap pattern (GAP) and a synchronization pattern (SYNC) from an encoded signal written to a disk, and a detection circuit that detects a gap pattern (GAP) and a synchronization pattern (SYNC) from an encoded signal written to a disk. a detection check circuit that outputs a normal signal when a gap pattern and a synchronization pattern are detected in this order; and a detection check circuit that outputs a normal signal when a gap pattern and a synchronization pattern are detected in this order. The apparatus includes an error signal output circuit that checks whether a normal signal is output and outputs an error signal when a normal signal is not output.

[Operation] According to the present invention, checking of the encoded signal to be written to the disk is performed in parallel with the writing operation. That is, if the detection circuit detects both the GAP and 5YNC patterns from the encoded signal in this order, it will output a normal signal; otherwise, it will not output a normal signal, so one of the patterns is missing. In this case, an error signal is output from the error signal output circuit. As a result, it is possible to notify that there is an abnormality in writing.

[Examples] Examples of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of a data write circuit and its test circuit according to an embodiment of the present invention.

Write data a given from a host device (not shown) is parallel-to-serial converted in a parallel-to-serial conversion circuit 1 to become serial write data b. This write data b is encoded by the encoding circuit 2 to become an encoded signal C and written to a magnetic disk medium (not shown). On the other hand, this encoded signal C
is input to the shift register 3, where it is converted into a parallel signal d. Parallel signal d is sent to parallel decoder 4
has been entered. The parallel decoder 4 detects a GAP pattern and a 5YNC pattern from the parallel signal d, and outputs a GAP detection signal f and a 5YNC detection signal g. The GAP detection signal f is stored in a memory circuit (MEM) 5. Further, the 5YNC detection signal g is applied to one input of the AND gate 6. This AND gate 6
The output of the memory circuit 5 is input to the other input.

The output i of the AND gate 6 is stored in a memory circuit (MEM) 7. The outputs of these memory circuits 5 and 7.

i is input to the NAND gate 8. Therefore, N.A.
The output of the ND gate 8 is "0" only when GAP and 5YNC are detected in this order, otherwise it is "°'1".
becomes. The D-type flip-flop 9 latches the output k (normal signal) of the NAND gate 8 with the check signal 1 output during the DATA write period, and sends the error output m to the host device (
(not shown).

In this circuit, the shift register 3 and the pattern 4 decoder 4 constitute a detection circuit, and the memory circuits 5 and 7, the AND gate 6 and the NAND gate 8 constitute a detection check circuit,
D-type flip-flop 9 constitutes an error signal output circuit.

Next, the operation of the circuit of this embodiment configured as described above will be explained.

FIG. 2 shows a time chart during normal operation. WRT signal e
When becomes '1' and starts the write operation, the pattern decoder 4 first detects the GAP pattern. Therefore, the detection signal f becomes '1' and this is held in the memory circuit 5. Subsequently, the pattern decoder 4 detects the GAP pattern. Since the decoder 4 detects 5YNC bytes, the detection signal g becomes "i". Since the output of the memory circuit 5 also maintains 1", the AND gate 6
The output i of the NAND gate 8 becomes "1", which is stored in the memory circuit 7. When the check signal i becomes "1" during the writing period of the data section (DATA), the output of the NAND gate 8 becomes "1". Since it is 0°', 0° is latched in the D-type flip-flop 9, and the error output m remains at "O".Therefore, the write operation continues.

Next, the case where 5YNC bytes are not sent from the host device will be explained with reference to the time chart in FIG. When the WRT signal e becomes “1” and the write operation starts,
The pattern decoder 4 detects the GAP pattern, and the output of the memory circuit 5 becomes "1'' in the same way as above. However, since the 5YNC byte is not detected, the detection signal g becomes "0".
”, the output j of the memory circuit 7 also remains at “0”. Therefore, the output remains at “1”. Therefore, the disk part (
DATA) check signal g is “1” during the write period.
”, the output remains “1”, so the D-type flip-flop 9 latches “1”, and the error output m becomes “1”, so the magnetic disk drive detects the error. , aborts the write operation and reports it to the higher-level device.

As described above, according to the present device, it is possible to detect the omission of each pattern of GAP and 5YNC bytes, and therefore it is possible to prevent abnormal data from being written to the disk medium.

[Effects of the Invention] As explained above, the present invention can detect an abnormality in write data by checking the presence or absence of a GAP pattern and a 5YNC byte pattern in an encoded serial write signal. This has the effect of being able to prevent writing.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a data writing circuit and a test circuit according to an embodiment of the present invention, Fig. 2 is a timing diagram showing the operation of the test circuit when writing a normal signal, and Fig. 3 is an abnormality of the test circuit. FIG. 4 is a timing diagram showing the operation during signal writing, and is a diagram showing the structure of write data.

Claims (1)

[Claims] (1) A detection circuit that detects a gap pattern and a synchronization pattern from an encoded signal written to a disk, and a detection circuit that outputs a normal signal when the gap pattern and synchronization pattern are detected in this order by this detection circuit. A check circuit and a check signal output during the data pattern output period of the encoded signal are used to check whether or not a normal signal is output from the detection check circuit, and when a normal signal is not output, an error signal is output. What is claimed is: 1. A magnetic disk drive comprising: an error signal output circuit.