GB2242561A

GB2242561A - Magnetic disc drives

Info

Publication number: GB2242561A
Application number: GB9103406A
Authority: GB
Inventors: Masayuki Urabe
Original assignee: Tokico Ltd
Current assignee: Tokico Ltd
Priority date: 1990-02-20
Filing date: 1991-02-19
Publication date: 1991-10-02
Also published as: DE4105276A1; JPH03242864A; GB9103406D0

Abstract

The disclosed magnetic disk drive device is provided with a counter for counting the number of sectors which have passed by a magnetic head, a judging circuit for making a determination as to whether the number of sectors counted by the sector counting means is not less than the sector number of a target sector and does not exceed a maximum sector for reading/writing a data and a controller for controlling the timing of the data read/write operation, such that: i) when the judging means has judged that the number of sectors counted is not less than the sector number of the target sector and does not exceed the maximum sector, the data read/write operation commences immediately; and ii) when the judging means has not judged that the number of sectors counted is not less than the sector number of the target sector and does not exceed the maximum sector, the data read/write operation commences when the sector counting means has counted up to the sector number of the target sector. <IMAGE>

Description

MAGNETIC DISK DRIVE DEVICE AND METHOD FOR CONTROLLING THE SAME

Background of the Invention Field of the Invention

The present Invention pertains to a magnetic disk drive device and a method for controlling a magnetic disk drive device, and in particular, to a magnetic disk drive device which provide very fast access times during both read and write operations, and controlling a method for achieving the same.

Prior Art

For control of read and write operations by the magnetic heads of the disk drive. address data LBA (logic block address) is supplied from the host computer. on which basis the target cylinder and sector, as well as the corresponding magnetic head are determined. The designated magnetic head then performs a seek operation for the target cylinder, after which a read operation commences so as to locate the target sector. After the position of the target sector has been identified on the basis of the position of sector zero which has already been found, a data read operation commences which continues for a predetermined sector count, after which the read gate closes and the data read operation therefore terminates.

For the timing control as explained above, the point in time at which the designated target sector is considered to be in position for the start of a read operation is determined based on a sector count up to a predetermined 1 1 f 1 value which begins after the detection of the index pulse written at sector zero. The point In time at which the read operation is terminated Is based on a sector count starting at the beginning of the read operation which continues up to a second predetermined value. Thus, when sector zero is identified immediately at the onset of a seek operation for the target sector, the target sector can be determined to be In position for the read operation after counting to a value which is at most the total number of sectors in a single track minus one, in other words, the count can be carried out is slightly less time than that required for one rotation of the magnetic disk.

However, as shown in Fig. 3(a), when for example sector one Is positioned adjacent to the head used for counting sectors at the beginning of the read operation, sector zero from which the count begins is not detected until after the time required to count the total number of sectors in one track minus one, that is, sector zero is not detected until after nearly one complete revolution of the magnetic disk. Thus, in this case when the seek operation begins at sector one, a read operation does not begin until after one revolution of the disk plus the time required for the sector count up to the designated value for the target sector minus one. It can therefore be seen that the time required from the start of the seek operation up to the beginning of the read operation can potentially be as long as nearly the time required for two complete disk revolutions.

For this reason, the time required to read 18 kbytes of data will be in the range of from 33 msec to 50 msec which is 2 1 i 1 unacceptably long.

Summary of the Invention

In consideration of the above described problem, It is an object of the present Invention to a provide magnetic disk drive device which capable of accessing very fast during both read and write operations, and method for controlling the same.

In a first aspect of the present Invention. there is provided a magnetic disk drive device. which performs a data read/wrIte operation, in response to a command from a host computer, said magnetic disk drive device comprising:

(A) a sector counting means for counting the number of sectors which have passed by a magnetic head, wherein said sector counting means Is reset to zero when a.predetermined sector passes by said magnetic-head; (B) a judging means for making a determination -as to whether the number of sectors counted by said sector counting means is not less than the sector number of a target sector and does not exceed a maximum sector for reading/writing a data; and (C) a controller for controlling the timing of said data read/write operation, such that:

1) when said judging means has judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences. immediately; and ii) when said judging means has not judged that the number of sectors counted is not less than the sector 3 number of said target sector and does not exceed said maximum sector, said data read/write operation commences when said sector counting means has counted up to the sector number of said target sector.

In a second aspect of the present Invention, there is provided a method for controlling magnetic disk drive device. which performs a data read/write operation, in response to a command from a host computer, said method comprising the steps of:

(A) counting the number of sectors which have passed by a magnetic head, but being reset to zero when a predetermined sector passes by said magnetic head; (B) judging as to whether the number of sectors counted by said sector counting means is not less than the sector number of a target sector and does not exceed a maximum sector for reading/writing a data; and (C) controlling the timing of said data read/write operation, such that:

i) when it has been judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences immediately; and ii) when It has not been judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences when the number of sectors counted has reached the sector number of said target sector.

4 1 1 1 1 1 i 1 1 Brief Description of the Drawings

Fig.1 is a block diagram showing a counting device Incorporated in a magnetic disk drive device In accordance with a preferred embodiment of the present invention.

Fig. 2 Is a flow chart showing the read access operation of the embodiment.

Fig. 3 is a wave form chart Illustrating the read access operation of the embodiment.

Detailed Description of the Preferred Embodiment

In the following section, a preferred embodiment of the present invention will be described with reference to the drawings.

Fig.1 shows a counting device incorporated in the disk drive apparatus of the present embodiment. whereby a count is kept of pulses which are generated when each sector on the magnetic disk passes by a magnetic head. As the figure shows, the counting device is composed of a counter 1 and CPU (central processing unit) 2.

As described above, when a predetermined region in each sector passes passes by the head, a pulse is generated which Is referred to as a sector pulse.

The above-mentioned counter 1 is incremented with each successive sector pulse. The overall operation of the magnetic storage device is controlled through operation of the above mentioned CPU 2.

In the device of the present embodiment, the magnetic disk is such that each concentric track is made up of 36 sectors numbered from 0 to 35. At the leading field of each sector. excluding sector 0, a sector marker signifying the sector is recorded on the disk. When this marker passes b3F the magnetic head, the above mentioned sector pulse is generated and supplied to counter 1. The number stored in counter 1 is encoded over six bits, thus counter 1 is capable of holding a number from zero to sixty four. and is therefore able to count all of the sectors making up one track. An Index marker signifying sector 0 is written at the leading portion of sector 0 rather than a sector marker, and when this index marker passes by the head, an index pulse is generated and supplied to counter 1, whereby counter 1 Is caused to reset to zero.

In the following section, the operation of CPU 2 will be described with reference to a flow chart of 2.

As mentioned above, each track is constituted of 36 sectors numbered from 0 to 35.

CPU 2 starts a read operation. First of all, in step S1, CPU 2 determines the target cylinder, sector and the corresponding magnetic head on th6 basis of an address data LBA supplied from a host computer. In step S2, CPU 2 judges whether or not the present cylinder is the target cylinder. Here. when the result of the judgment Is [NO], that is to say, when the present cylinder is the target cylinder, CPU 2 goes to step S3. On the other hand, when the result of the judgment is [YES], that is to say, when the present cylinder is the target cylinder, CPU 2 goes to step S4. In step S3, CPU 2 causes the corresponding magnetic head to seek the target cylinder on the magnetic disk. After the corresponding magnetic head sought the target cylinder, CPU 2 6 j 1 i 1 1 j i 1 i 1 1 goes to step S4.

In step S4, CPU 2 judges whether or not the target sector Is a maximum sector, sector 35 In the present embodiment.

Here. when It Is determined that the target sector is maximum sector as the result of the judgment, CPU 2 goes to step S17. wherein CPU 2 performs an ordinary read operation. that Is to say. after a count Is carried out in counter 1, beginning with sector 0 and counting successively until the target sector number is reached. at which time the read operation commences. In step S5. the absolute read data length in sectors is added to the target sector number, after which a determination is made as to whether the result of this addition operation ex'ceeds the maximum sector number or not. When the result of this judgment is [NO], the routine proceeds to step S17 and an ordinary read operation is carried out. When the result of this judgment is [YES]. the routine proceeds to step S6.

In step S6, the count value is then read out from counter 1.

In step 7, a determination is made as to whether the target sector number exceeds the count value or not. When the result of this judgment is [YES]. the routine proceeds to step S17 and an ordinary read operation is carried out, that Is. after a count Is carried out in counter 1, beginning with sector 0 and counting successively until the target sector number is reached, at which time the read operation commences.

When the result of this judgment is [No], the routine 7 proceeds to step S8, as the read operation can be commenced with the target sector. In step 8, 1 is added to the count value read out from counter 1 and the result of this addition operation Is set and stored as a read beginning sector number signifying the sector with which a data read operation is commenced. That is to say, the sector number of the sector next to the sector which is presently adjacent to the magnetic head Is set and stored as a read beginning sector number which is different from the target sector number from the host computer. Also. the original target sector number supplied from the host computer. the sector number of the sector before the sector which is presently adjacent to the magnetic head, is set and stored as a target sector number which is different from the above mentioned read beginning sector number. In step S9, the data read operation commences with the sector signified by the read beginning sector number set in step S8. In step S10, a data read operation is carried and a read sector count is incremented by one, which is set to the count value equal to the read beginning sector number at first, every time a read sector passes by the magnetic head. By the way. the above mentioned read sector count is carried out and stored in CPU 2. which is different from the above mentioned count carried out in counter 1. In step S11, CPU 2 repeats the processing of step S9 and step S10 until the read sector count incremented in step S10 exceeds the maximum sector number which designates the a maximum sector for reading/writing the data. And when the read sector count exceeds the maximum sector number, the routine proceeds to step S12. In step S12, CPU 2 once stops 8 il P 1 the read operation. And the read beginning sector number as described above Is updated to the original target sector number supplied from the host computer. because sector 0 passes again by the magnetic head and an ordinary read operation can be carried out. Also, the read sector count Is caused to reset to zero, at the time when sector 0 passes by the magnetic head.

In step S13. the read sector count Is kept of sector pulses, beginning with sector 0 and counting successively each sector pulse. In step S14, the read sector count Is incremented by one, every time a sector pulse is read out by the magnetic head. Next, the routine proceeds to step S15. In step S15, a determination is made as to whether the read sector count is equal to the read beginning sector number or not. When the result of this Judgment is [YES], the routine proceeds to step S16. When the result of this judgment Is [NO], the routine proceeds back to step S13 and a count is successively kept of sector pulses.

In step 16, if the head reading presently data is a head numbered maximum numeral value, the magnetic head then performs a seek operation for the next cylinder, after which the head for reading is changed to a new corresponding head. such that a read operation commences from head 0 and sector 0.

In step S17, when the sector corresponding to the predetermined read beginning sector (or the target sector) is reached, an ordinary read operation commences.

This routine terminates all processing, after the read operation in step S17.

9 11 As described above, with the disk drive devise in accordance of the present embodiment, after a read command from the host computer is accepted, the read operation can be commenced with the sector next to the sector which is presently positioned adjacent to the magnetic head, without waiting for detecting the Index pulse written at sector 0. That is to say, when the access to somewhere in the region of from sector 0 to sector 35 commences directly after the detection of the index pulse. with a conventional disk drive, as Fig. 3(a) shows, dummy signal is generated from each sector, until the next index pulse is read out after nearly one complete disk revolution. It can therefore be seen that the time required from the start of the seek operation up to the beginning of the read operation can potentially be as long as nearly the time required for two complete disk revolutions.

In contrast, with the present embodiment about the same case, as Fig. 3(b) shows, because the read gate timing is controlled based on a count value, the desired access terminates by nearly one complete disk revolution, without the generation of dummy signal during nearly one complete disk revolution.

While one preferred embodiment of the present invention is described above. it is not intended to limit the present invention to this embodiment. The present invention can provide very fast access time during a write operation as well as a read operation. A write operation is commenced after receiving completely data to be written from a host d i computer.

Accordingly. a data buffer is provided having a storage capacity equal to twice the storage capacity of an ordinary track on the disk. A write operation can then be suitably carried out after the data from the host computer has been consecutively stored In this data buffer In response to the beginning sector number for the write operation.

11 ( t What Is claimed is:

1. A magnetic disk drive device. which performs a data read/write operation, in response to a command from a host computer. said magnetic disk drive device comprising:

(A) a sector counting means for counting the number of sectors which have passed by a magnetic head, wherein said sector counting means is reset to zero when a predetermined sector passes by said magnetic head; (B) a judging means for making a determination as to whether the number of sectors counted by said sector counting means is not less than the sector number of a target sector and does not exceed a maximum sector for reading/writing a data; and (C) a controller for controlling the timing of said data read/write operation, such that:

i) when said judging means has judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences immediately; and ii) when said judging means has not judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences when said sector counting means has counted up to the sector number of said target sector.

2. A magnetic disk drive device in accordance with claim 1 above, wherein said controller Is such that:

12 j j 1 i i) when said judging means has judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences Immediately and continues up to said maximum sector, and after said sector counting means Is reset to zero when said predetermined sector passes by said magnetic head, said data read/write operation again commences when said sector counting means has counted up to the sector number of said target sector and said data read/write operation continues until a sector adjacent to said sector with which said data read/write operation has first commenced; and ii) when said judging means has not judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences when said sector counting means has counted up to the sector number of said target sector and said data read/write operation continues until said maximum sector.

3. A magnetic disk drive device in accordance with claim 1 above, wherein said sector zero is provided with an index marker; when said index marker passes by said magnetic head, an Index pulse is generated and supplied to said sector counting means, whereby said sector counting means Is reset to zero.

4. A magnetic disk drive device in accordance with claim 1 above, which Includes a central processing iinit; 13 whereby said judging means and said controller are constituted.

5. A magnetic disk drive device in accordance with claim 1 above, which further comprises a data buffer for storing temporarily a data which has been read out from a magnetic disk/a data from said host computer.

6. A method for controlling magnetic disk drive device, which performs a data read/write operation, In response to a command from a host computer, said method comprising the steps of:

i) when it has been judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences immediately; and ii) when It has not been judged that the number of sectors counted Is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences when the number of' sectors counted has reached the sector number of 14 1 i i C 1 i said target sector.

7. A method for controlling magnetic disk drive device in accordance with claim 6 above. whereby said step of controlling Is such that:

i) when It has been judged that the number of sectors counted Is not less than the sector number of said target sector and does not exceed said maximum sector. said data read/write operation commences immediately and continues up to said maximum sector, and after having been reset to zero when said predetermined sector passes by said magnetic head, said data read/write operation again commences when the number of sectors counted has reached the sector number of said target sector and said data read/write operation continues until a sector adjacent to said sector with which said data read/write operation has first commenced; and ii) when it has not been judged that the number of sectors counted is not less than the sector number of said target sector and does not exceed said maximum sector, said data read/write operation commences when the number of sectors counted has reached the sector number of said target sector and said data read/write operation continues until said maximum sector.

8. A method for controlling magnetic disk drive device in accordance with claim 6 above. whereby the number of sectors counted is reset to zero in response to an index pulse from said sector zero.

9. A method for controlling magnetic disk drive device in is 1 1 .ccordance with claim 6 above, said method further comprising the step of storing temporarily a data which has been read out from a magnetic disk/a data from said host computer.

10. A magnetic disc drive device substantially as described herein with reference to the accompanying drawings.

11. A method for controlling a magnetic disc drive substantially as described herein with reference to the accompanying drawings.

1 16 1,p Published 1991 at The Patent Office. Concept House. Cardiff Road. Nzxpos- z. Gwent NP9 I RH. Further copies maybe obtained from Sales Branch. Unit 6. Nine Mile Point. Cii-mfelinfach Cross Keys. Newport- NPI 7HZ. Printed by Multiplex techniques lid. St Man Cray. Kent-