JPS60230233A - Magnetic disk read-out controlling system - Google Patents

Abstract

PURPOSE:To read out exactly data part information of a sector having a CRC error by inhibiting the output of an identifying part CRC error signal in accordance with the counted result of a sector count means, and also outputting forcibly a identifying part comparison coincidence signal. CONSTITUTION:Counting is executed in accordance with an AM detecting signal by a sector count arithmetic circuit 14 which is made countable by an index signal, and when it goes to a set value, a start signal is sent out to a read controlling circuit 23, coincidence signal outputting circuit 15 and an inhibiting signal outputting circuit 16; the circuit 15 outputs an ID coincidence signl to an OR gate 21 by the timing corresponding to an AM byte of data part of an object sector, and the circuit 16 outputs an error inhibiting signal to an AND gate 22. On the other hand, the circuit 23 supplies read-out information from the object sector, to an SP converting circuit 17 and a CRC checking circuit 20, a data of the circuit 17 and a target address are compared by an ID part comparing and arithmetic circuit 19 and the ID coincidence signal is supplied to the gate 21, and the circuit 20 supplies a CRC error signal to the gate 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic disk controller that controls a magnetic disk device, and particularly to a magnetic disk read control method suitable for the case where a CRC error occurs in an identification section.

[Technical background of the invention and its problems] In general, each sector (format) of a magnetic disk is composed of a pair of an IDCII section and a DATA section. Identification information (address information) of the corresponding sector is recorded in the ID section. For example, in read mode, when this identification information matches the target address, the recorded information in the DATA section immediately after is read out. . However, if a CRC error occurs in the ID section due to a scratch on the disk media (media defect), the ID section cannot be recognized, so reading the information in the DATA section immediately after is difficult and is generally stopped. It was a target.

In this case, it is conceivable to decode the analog read signal from the magnetic disk device using special processing operations and obtain the information in the DATA section. However, this method is inefficient and difficult to apply.

Furthermore, in the pre-recording stage, restoration is possible by applying a method (for example, long gap method) that changes the recording position of the ID section, but this type of method cannot be used for information that has already been recorded. It has no effect because it is not applicable.

[Purpose of the Invention] This invention was made in view of the above circumstances, and its purpose is to provide a method for reliably reading data (DATA) section information of sectors with CRC errors in the identification (ID) section, while having a simple configuration. The purpose of the present invention is to provide a magnetic disk read control method that can be used to read data from a magnetic disk.

[Summary of the Invention] The present invention is provided with sector counting means that is enabled for counting by an index signal from a magnetic disk device and counts up to a set value corresponding to a target sector by an AM detection signal or a sector pulse signal. When the sector counting means counts up to the set value, the discrete starts and read timing control is performed. Furthermore, in accordance with the count up to the set value, the output of the identification unit CRC error signal is prohibited, and an identification unit comparison match signal indicating the match between the identification information of the identification unit and the target address is forcibly output.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a disk data read circuit (in a magnetic disk controller) to which the present invention is applied. The configuration shown in FIG. 1 is for reading data from a small magnetic disk that does not have a servo surface. In FIG. 1, 11 is an index signal (index pulse) IDX from a magnetic disk device (not shown).
12 is a flip-flop (hereinafter referred to as F/F) that toggles P and outputs a toggle signal TGL. 13 is the toggle signal T from F/F 12
F/ that toggles GL1 and outputs toggle signal TGL2.
F (flip-flop). Above AM detection signal A
MFUND is a signal indicating AM (address mark) byte detection. This AM byte is a non-flux change location provided to indicate the sector position (10th part and DATA part) on the track, as shown in the track format (of an IT disc) in FIG. 2. Note that 10 (by It) part, which is one component of the sector, is the PLO byte for basic clock generation, and the AM
byte, 5YNC (sync) byte, address information (sector address information), and CRC byte (character)
Consists of. Also, the other component of the sector, DAT
Part A is PLO byte, A M Hyde, 5YNC
It consists of bytes, data, and CRC bytes (plus FCC bits).

Referring again to FIG. 1, 14 is a sector count calculation circuit that is enabled for counting in response to the toggle signal TGL from the F/F 11. The sector count calculation circuit 14 counts from the track index to the sector immediately before the target (read target) sector according to the toggle signal TGL2 from the F/F 13, and provides a read start signal for starting data read from the target sector. 5TR
Output T.

15 is a pseudo ID match signal IDC1 based on the read start signal 5TRT from the sector count calculation circuit 14.
16 is a prohibition signal output circuit. The prohibition signal output circuit 16 generates an error prohibition signal ERI for forcibly intruding an IDICRC error based on the signal 5TRT from the sector count calculation circuit 14.
Generates NH. 17 is an SP conversion circuit that converts the read information RDDATA from the magnetic disk device from serial to parallel; 18 is the address of the target sector (target address)
This is a target address holding unit that holds . 19 detects a match between the address information in the output data from the SP conversion circuit 17 and the target address from the target address holding section 18;
a 10-part comparison calculation circuit that outputs an ID match signal IDC2;
20 is read information RDDATA from the magnetic disk device
This is a CRC check circuit for. The CRC check circuit 20 outputs a CRC error signal ER1 when detecting a CRC error.
Output. Reference numeral 21 denotes an OR gate that performs an OR operation between the ID match signal IDCl from the match signal output circuit 15 and the ID match signal IDC2 from the ID section comparison calculation circuit 19, and outputs the ID match signal IDC; and 22, a CRC from the CRC check circuit 20; The error signal ERI and the error prohibition signal ERINH from the prohibition signal output circuit 16 are ANDed and CR
An AND gate 23 outputs a C error signal ER, and 23 is a read control circuit. The read control circuit 23 receives a read start signal 5TRT from the sector count calculation circuit 14,
In response to the 10 match signal IDC1 from the OR gate 21 and the CRC error signal ER from the AND gate 22, various timing signals such as a read timing signal (read gate signal) RDGT are generated. In the configuration shown in FIG. 1, the sector count calculation circuit 14, the coincidence signal output circuit 15, the prohibition signal output circuit 16, the 10th section comparison calculation circuit 19, and the read control circuit 23 are realized by, for example, a one-chip microcomputer. .

Next, the operation of one embodiment of the present invention will be explained with reference to the timing chart of FIG. First, when reading a sector, a setting value corresponding to the target sector, for example, a target sector number, is initially set in the sector count calculation circuit 14.

Assume that this target sector number is "3". Also,
In this state, from the magnetic disk device to the F/
It is assumed that the index signal IDXP is supplied to F11. F/F 11 is the index signal IDXP
is toggled, and a toggle signal TGL is output as shown in FIG. This toggle signal TGL is supplied to the sector count calculation circuit 14. As a result, the sector count calculation circuit 14 enters the count enable state. Also,
AM detection signal AMFUND from the magnetic disk device is F
/ F 12 is supplied. The F/F 12 toggles this AM detection signal AMFUND and outputs a toggle signal TGLI to the F/F 13. This toggle signal TGL1
As is clear from FIG. 3, one period corresponds to one sector. F/F 13 toggles the toggle signal TGLI from F/F 12, and toggle signal TGL2
is output to the sector count calculation circuit 14. The sector count calculation circuit 14 performs a count up operation in response to the state transition of the toggle signal TGL2 from the F/F 13 in the count enable state. That is, the sector count calculation circuit 14 counts the number of sectors (sector number + 1) from the index indicating the start position of each track. In this embodiment, the index signal IDXP is toggled by F/F 11, and F/F 12,
Since the AM detection signal AMFUND is toggled in two stages by 13, processing is possible even if the sector count calculation circuit 14 is implemented by a low-speed 1-chip microcomputer. In addition, in this embodiment, the condition for correctly counting the number of sectors from the index (according to AM bytes) is that there is no synchronization error (PLO byte, AM byte, 10th part, D
The 5YNC byte indicating the beginning of the ATA section could not be determined, and the I
There should be no error that the information in the D section and the DATA section cannot be read.

The sector count calculation circuit 14 checks whether the count value matches the target sector number set above. When the sector count calculation circuit 14 detects that the count value matches the target sector number,
In other words, the sector immediately before the target sector (in this example, sector 2)
When detected, a read start signal 5TRT is output as shown in FIG. This signal 5TRT is supplied to the match signal output circuit 15, prohibition signal output circuit 16, and read control circuit 23.

The read control circuit 23 outputs the read timing signal RDGT shown in FIG. 3 to the magnetic disk device in response to the signal 5TRT from the sector count arithmetic circuit 14, and performs normal sector reading for the target sector (ID part therein). let By this sector reading, read information RDDAT is read from the target sector (sector 3) of the magnetic disk.
A (ID part data) is the SP conversion circuit 17 and CR
The signal is supplied to the C check circuit 20. The SP conversion circuit 17 performs serial/parallel conversion on the read information RDDATA according to timing control of the read control circuit 23.

Converted output data from the SP conversion circuit 17 is supplied to an ID section comparison calculation circuit 19. The ID section comparison calculation circuit 19 converts the address information (IDI) in the output data from the SP conversion circuit 17 in accordance with the timing control of the read control circuit 23.
E-specific information) and the target address held in the target address holding unit 18 are compared.

The CRC check circuit 20 also includes a read control circuit 23.
Based on the CRC byte of the ID section (the next timing for the DATA section) in the read information RDDATA from the magnetic disk device,
A CRC check (in this case, a CRC check of the ID section) is performed. Now, enter C in the ID part of the target sector (sector 3).
Assuming that there is an RC error, the CRC check circuit 2
0 outputs the CRC error signal ER1 at the corresponding timing.

On the other hand, based on the read start signal 5TRT from the sector count calculation circuit 14, the prohibition signal output circuit 16 converts the level inverted signal of the signal 5TRT into an error prohibition signal ER.
Output as INH (see Figure 3). Further, the coincidence signal output circuit 15 outputs the signal 5TRT from the sector count calculation circuit 14 to the DAT of the target sector as shown in FIG.
At the timing corresponding to the AM part-time job of A part,! It is output as a D match signal IDC1.

Error prohibition signal ERINH from prohibition signal output circuit 16
is supplied to one input terminal of the AND gate 22.

The other input terminal of the AND gate 22 receives an output signal from the CRC check circuit 20 (CRC error signal ER1).
) is supplied. The AND gate 22 outputs (IDICR) regardless of the CRC error signal ERI from the CRC check circuit 20 during the period when the error prohibition signal ERINH from the prohibition signal output circuit 16 is at the "L" level (LOW level).
A “L” level CRC error signal ER (indicating no C error) is output to the read control circuit 23. As a result, even if there is a CRC error in the ID section of the target sector, it is ignored and treated as if there were no CRC error in the ID section. As shown in FIG. 3, the error inhibition signal ERINH is returned to the "L" level at a timing corresponding to the AM byte of the DATA portion of the target sector. On the other hand, the pseudo 10 match signal IDC1 from the match signal output circuit 15
is supplied to one input terminal of the OR gate 21. As a result, the OR gate 21
Regardless of whether address matching is detected or not, a valid ID matching signal IDC is output to the read control circuit 23 as if address matching was normally detected. The read control circuit 23 receives the ID match signal ID from the OR gate 21.
In response to C, the read timing signal RDGT is output to the magnetic disk device as shown in FIG. 3 (to read the DATA part of the target sector), and
section) to perform normal sector reading.

In the above embodiment, a magnetic disk without a servo surface has been described, but the present invention is not limited to this. The present invention is applicable to, for example, the hard sector method (a method in which a track is divided into fixed lengths using index pulses and sector pulses) and the soft sector method (a method in which sectors are assigned to fixed or variable lengths using AM bytes) for magnetic disks with servo surfaces. It is also applicable to both types. However, in the hard sector method, it is necessary to use a sector pulse signal instead of the AM detection signal AMFUND.

In this case, only one stage of F/F (flip-flop) for toggle is required. In addition, in the above embodiment, the F/F for toggle
Although a case has been described in which a flip 70 is provided, for example, if the sector count calculation circuit 14 is constituted by a high-speed hardware circuit, this type of F/F is not necessarily necessary.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to reliably read the data (DATA) part information of a sector with a CRC error in the identification (ID) part, although it has a simple configuration. . That is, according to the present invention, when an ID section failure occurs due to damage to the magnetic disk medium, a disk file can be repaired very easily by commands from the host side.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a disk data read circuit to which the present invention is applied, FIG. 2 is a diagram showing a track format, and FIG. 3 is a timing chart for explaining the operation. 11-13...Flip 70 knob (F/F), 14.
...Sector count calculation circuit, 21...OR gate,
22...AND gate, 23...Read control circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (1)

[Claims] A sector counting means is enabled for counting by an index signal from a magnetic disk device, and counts up to a set value corresponding to a target sector by an AM detection signal or a sector pulse signal, and a discrete is started according to the count result of this sector counting means. means for performing read timing control; means for inhibiting the output of an identification section CRC error signal according to the count result of the sector counting means; 1. A magnetic disk read control method, comprising: means for forcibly outputting.