GB2234098A - Disk drive/host computer interfacing - Google Patents

Disk drive/host computer interfacing Download PDF

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Publication number
GB2234098A
GB2234098A GB9015902A GB9015902A GB2234098A GB 2234098 A GB2234098 A GB 2234098A GB 9015902 A GB9015902 A GB 9015902A GB 9015902 A GB9015902 A GB 9015902A GB 2234098 A GB2234098 A GB 2234098A
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United Kingdom
Prior art keywords
disk
bytes
error correction
central device
data
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB9015902A
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GB9015902D0 (en
Inventor
Masayuki Urabe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Tokico Ltd
Original Assignee
Tokico Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tokico Ltd filed Critical Tokico Ltd
Publication of GB9015902D0 publication Critical patent/GB9015902D0/en
Publication of GB2234098A publication Critical patent/GB2234098A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/10—Digital recording or reproducing
    • G11B20/18—Error detection or correction; Testing, e.g. of drop-outs
    • G11B20/1833—Error detection or correction; Testing, e.g. of drop-outs by adding special lists or symbols to the coded information
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F11/00—Error detection; Error correction; Monitoring
    • G06F11/07—Responding to the occurrence of a fault, e.g. fault tolerance
    • G06F11/08—Error detection or correction by redundancy in data representation, e.g. by using checking codes
    • G06F11/10—Adding special bits or symbols to the coded information, e.g. parity check, casting out 9's or 11's

Abstract

To enable magnetic disk apparatus which stores data with a given number of error correction code (ECC) bytes to exchange data with a host computer using fewer ECC bytes, control means in the apparatus is responsive to a read request from the computer to send to the computer the requested data plus a portion only of the ECC bytes read from the disk, Fig. 3. In response to a write request from the computer, the control means causes the data and associated ECC bytes from the computer to be stored, together with additional ECC bytes to make up the given number, Fig. 4c. The additional bytes are obtained, Fig. 4b, by a disk read operation. <IMAGE>

Description

_el. X-73 'D 11-3 MAGNETIC DISK APPARATUS
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an external meMory means using a magnetic disk apparatus. Especially, the magnetic disk apparatus of the present Invention Is provided for the situation in which a disk having Installed a disk Error Correction Code (ECC) (hereafter, Error Correction Code will be referred to as ECC) number of bytes, and the host computer central device number of bytes, are not equal, in the case in which it is highly desirable to have proper interface matching between the magnetic apparatus and the central device.
Prior Art
A computer may be used as the central device in a network, and a magnetic disk apparatus may be one of the peripheral devices used with the computer.
A computer is provided in the above-mentioned central device, and the computer contains data and ECC to perform data error correction.
The above-mentioned magnetic disk apparatus comprising:
a disk on which is written the data and disk ECC to manage said data; and a head, to write said data and disk ECC to the disk, and to read out said data and disk ECC from the disk.
The head of the above magnetic disk apparatus writes the data and ECC on the disk; data and ECC on the disk is read out by means of a Hard Disk Controller (HDC) provided between the magnetic disk apparatus and the above-mentioned computer.
This Hard Disk Controller (HDC) is supported by, for example, 4-byte, 6byte, or 7-byte ECC numbers of bytes. However, if in the computer the ECC number of bytes is, for example, 4 bytes, then in order to be compatible, the disk ECC number of bytes should also be 4 bytes.
In this case, the magnetic disk apparatus disk ECC 7 bytes long, or could have the magnetic disk apparatus could have disk ECC 4 bytes long. The former ultimately has a miscorrection percentage one decimal place smaller tlan the latter when the magnetic disk apparatus head records data and then reads off an error.
This result, high performance efficiency, when the ECC is 7 bytes on the magnetic disk apparatus, is a point In its favor.
Next, the exchange of data and ECC between the abovementioned magnetic disk apparatus and the above-mentioned computer will be explained.
The "READ LONG" command and the "WRITE LONG" command has an ECC check use command for checking disk ECC, which are sent from the computer of the central device to the magnetic disk apparatus. The Hard Disk Controller controls the head of the magnetic disk apparatus and orders the head to write data values from the computer to the disk, and to read out data values from the disk.
In this case, the above-mentioned hard disk controller (HDC) writes or reads simultaneously ECC when data is written to the disk or read out from the disk in the magnetic disk apparatus.
The performance procedure of the "READ LONG" command of the prior art magnetic disk apparatus is, for example, as shown in Fig. 5.
That is: the magnetic disk apparatus receives the "READ LONG" command from the computer (Step SAl). In the magnetic disk apparatus, data is read from the disk at the head together with the disk ECC, X bytes (Step SA2). In the magnetic disk apparatus, "READ DATA + ECC X bytes" are transmitted to the computer (Step SA3). The ECC X bytes transmitted to the above-mentioned computer are sent to the central device ECC.
1 The prior art magnetic disk apparatus "WRITE LONG" command performance procedure is, for example, as shown in Fig. 6.
That is, the magnetic disk apparatus receives the command "WRITE LONG" from the computer (Step SB1). Then the magnetic disk apparatus requests from the computer 0VRITE DATA + ECC X bytes". When the magnetic disk apparatus receives the requested "WRITE DATA + ECC X bytes" from the computer (Step SB2), the head writes to the disk " WRITE DATA + ECC X bytes" (Step SB3).
However, the prior art magnetic disk apparatus using the above-mentioned command performance procedure has the following Inconveniences. In the case where the number of bytes of disk ECC X bytes differs from the number of bytes in the computer central device ECC number of bytes (this number of bytes equals Y bytes), and if X and Y are not equal, when a command is performed, the transmission of data between the magnetic disk apparatus and the computer is not compatible.
SUMMARY OF THE INVENTION
In the present invention, an ECC number of bytes set in the disk and a central device number of bytes differ from the proper interface matching of the computer for the purpose of being able to accept what is sent from the magnetic disk apparatus.
Then, In order to accomplish the above purpose, the peripheral memory means magnetic disk apparatus of the central device of the present Invention Is provided, with the following disk, head, and control means to control said head, comprising the following:
in the above-mentioned disk:
(a) data is written, (b) disk ECC to perform said data is written, and - 3 -4 i k (c) the number of bytes of the disk ECC is set higher than the central device ECC number of bytes set in the host computer; in the above-mentioned head:
(a) from the above-mentioned disk, data and dis ECC are read, (b) on the disk, data and disk ECC are written; In the above-mentioned control means:
(a) from the above-mentioned central device, in the case where disk ECC check read command for checking error correction code is sent out, from the disk at the head, and data and disk ECC are read, the read disk ECC of the number of bytes which is equal to the central device ECC number of bytes, and the read data, are sent to the above-mentioned central device; (b) from the above-mentioned central device, In the case where the disk ECC read command for writing disk ECC to the disk is sent to the disk head,' data and disk ECC provided from the central device are written.
The following effects are disclosed for this composition of the magnetic disk apparatus.
1. When the ECC check reading command is performed, the head of the magnetic disk apparatus reads data/disk ECC from the disk. The magnetic disk apparatus transmits the data and disk ECC redd at the head to the central device. At this time, the read disk ECC of the number of bytes which is equal to the central device ECC number of bytes and the read data are sent to the central device.
2. When the ECC check write command Is performed, the magnetic disk apparatus head writes dataldisk ECC sent from the control device to the disk.
From 1"and 2 above, in the magnetic disk apparatus, in which the disk ECC number of bytes is not equal to the 1 central device ECC number of bytes, it is possible for the central device to have proper interface matching.
BRIEF DESCRIPTIONS OF THE DRAWINGS
Fig. 1 shows the "READ LONG" command performance procedure of the present invention. I Fig. 2 shows the "WRITE LONG" command performance procedure of the present invention.
Fig. 3 shows the read data and ECC byte composition when performing the "READ LONG" command of the present Invention.
Fig. 4(a) shows schematically the composition of the "WRITE DATA and ECC X bytes" when performing the "WRITE LONG" command of the present invention.
Fig. 4(b) shows schematically the composition of the "READ DATA and the ECC Y bytes" when the "WRITE LONG" command of the present invention is performed.
Fig. 4(c) shows schematically the composition of the "WRITE DATA and the ECC Y bytes" when the "WRITE LONG" command of the present invention is performed.
Fig. 5 is a flowchart of the management procedure of the prior art "READ LONG" command.
Fig. 6 is a flowchart of the management procedure of the prior art "WRITE LONG" command.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the following, the first embodiment of the present invention will be explained with reference to the illustrations.
The present embodiment of the magnetic disk apparatus has a control means to perform a data and ECC read/write procedure by the head to the disk. In this magnetic disk apparatus, the Hard Disk Controller (HDC) (not shown in the illustration) is installed in the peripheral recording means host computer (the central device is not shown).
The above-mentioned host computer is designed to send to the abovementioned magnetic disk apparatus, via the above-mentioned Hard Disk Controller (HDC), the ECC check use "READ LONG" command and the 'VRITE LONG" command.
Again, in the above host computer, X bytes are set for the ECC number of bytes; and in the above-mentioned magnetic disk apparatus, Y bytes are set for the ECC number of bytes (however, X is less than Y). t However, when performing the "READ LONW command, the magnetic disk apparatus transmits data/ECC Y bytes read off from the disk, and with "READ DATA", the ECC X bytes, which are a portion of the ECC Y bytes, are transmitted to the host computer.
On one hand, when the "WRITE LONW command is performed, the magnetic disk apparatus writes the supplied data/ECC Y bytes from the host computer to the disk. However, in the above-mentioned magnetic disk apparatus, in the case where the number of bytes of the disk ECC and the number of bytes of the host computer central ECC differ, a function is provided to change the ECC number of bytes.
The above-mentioned "READ LONG" command is stated to be in agreement with Error Correction Code (ECC) check use read command in claim 1, and the above-mentioned "WRITE LONG" command is stated to agree with the Error Correction Code (ECC) check use write command in claim 1.
Next, the contents of the control means command procedure are explained with reference to Figs. 1 to 4.
READ LONG Command Management Procedure (with reference to Fig. 1) (Step SC1) The host computer sends the MEAD LONG" command to the magnetic disk apparatus, and this magnetic disk apparatus receives the sent out MEAD LONG" command from the host computer.
The host computer waits for the data transmission number from the magnetic disk apparatus of READ DATA (for 1 v X example, sector size equals 256 bytes, 512 bytes, 1024 bytes, etc.) + ECC bytes to be transmitted from the magnetic disk apparatus.
(Step SC2) The magnetic disk apparatus, in order to set thg Y bytes to the disk ECC number of bytes, the head from the disk reads the ECC 7 bytes.
In this case, to set disk ECC number of bytes Y-7, the above-mentioned head reads the program "READ DATA + ECC 7 bytes, as shown in Fig. 3.
(Step SC3) Next, the magnetic disk apparatus extracts ECC X bytes from the ECC Y bytes read from the above-mentioned disk.
However, In the above-mentioned magnetic disk apparatus, "READ DATA + ECC X bytes" then comes from the above-mentioned READ DATA and from extracted ECC X bytes, which Is transmitted to the host computer.
In this case, the host computer central ECC number of bytes Is X=4, and received "READ DATA + ECC 4 bytes are comprising the program arrangement in the part shown by the arrow in Fig. 3. Furthermore, to transmit ECC bytes, in the case of this embodiment, bytes are extracted from the start of ECC 7 bytes for 4 bytes; the range to extract the bytes, which is equal to the central device ECC number of bytes, is not limited.
WRITE LONG Management Procedure (see Fig. 2) (Step SD1) The above-mentioned host computer sends the "WRITE LONG" command to the magnetic disk apparatus, and the magnetic disk apparatus receives the %RITE LONW command sent from the host computer.
1 _n At the time of said command reception, the magnetic disk apparatus requests "WRITE DATA + ECC X bytes" to the host computer.
(Step SD2) From the magnetic disk apparatus in the above-mqntioned Step SD1 based on the request, the host computer sends the 'VRITE DATA + ECC X bytes" to the magnetic disk apparatus.
Moreover, the magnetic disk apparatus receives "WRITE DATA + ECC X bytes". In this case, the host computer ECC number of bytes is X=4, and "WRITE DATA + ECC 4 bytes" program composition is shown in Fig. 4(a).
(Step SD3) Next, in the magnetic disk apparatus, data is read off at the head from among the data on the disk together with ECC Y bytes. In this case, disk ECC number of bytes is Y=7, and the above-mentioned "READ DATA + ECC 7 bytes" program composition shown in Fig. 4(b).
(Step SD4) Next, in the above-mentioned step SD2, the magnetic disk apparatus receives ECC X bytes from the host computer; and in the above-mentioned Step SW, bytes from among the read ECC Y bytes are appended, and the number of received ECC bytes from the computer are regulated to Y bytes.
In this case, host computer central ECC number of bytes is X=4, and magnetic disk apparatus disk ECC number of bytes Is Y=7; the resulting above-mentioned append composition is shown in Fig. 4(c).
That is, in the ECC bytes shown in Fig. 4(c) [1, 2, 3, and 4], by the above-mentioned Step SD2, suitable ECC bytes are received from the host computer. Again, as shown in Fig. 4(c), ECC bytes [E, F, and G] in said step SD4, are suitably appended the remaining bytes.
-r (Step SD5) Next, the magnetic disk apparatus, by the above- mentioned step SD2, performs 'VRITE DATA" received from the host computer, appending ECC X bytes in the above-mentioned step SD5; the above-mentioned Step SD4 appending the remaining (Y-X) bytes. 1 Afterward, on the magnetic disk apparatus, the 'VRITE DATA + ECC X bytes + (Y - X) bytes" - "WRITE DATA + ECC Y bytes" to be written on the disk by the head.
That is, in the present example, In the case where the magnetic disk apparatus disk ECC number of bytes and the host computer central ECC number of bytes differ, in the magnetic disk apparatus, it is possible to transfer the data and the ECC from the central device to the magnetic disk apparatus by the %RITE LONW command, and from the magnetic disk apparatus to the central device by the MEAD LONG" command.
Furthermore, the above-mentioned magnetic disk apparatus Is able to accept host computer central ECC number of bytes most affected by the practical limitations of the magnetic disk apparatus ECC function; the host computer is then able to have proper interface matching.
Moreover, in the present embodiment, the operation method of the data when the "READ LOW' command/"WRITE LONG commands are executed is unlimited. In this case, the central device ECC consists of 4 bytes and the disk EC ' C consists of 7 bytes, however, the invention is not limited to these numbers "4" and "T; said byte numbers may optionally be set to other values "L" and '"K" (however, L is _less than K).
Again, in the above-mentioned magnetic disk apparatus control means, from the central device, received chntral device ECC is able to be sent back to the central device. In order for this to happen, it must be possible to check the normality of the connection of the above-mentioned - 9 qbmagnetic disk apparatus with the central device. This will increase the reliability of the magnetic disk apparatus.
11 1k 1

Claims (14)

What is claimed is:
1. A magnetic disk apparatus suitable for connection with a central device, the central device having central device Error Correction Codes consisting of a predetermined number of bytes, the magnetic disk apparatus comprising: (i) a disk on which Is written:
(a) data; (b) disk Error Correction Codes for correcting errors In the data, consisting of a number of bytes greater than the predetermined number of bytes of the central device Error Correction Code; (ii) a head for reading data and disk Error Correction Codes from the disk, and for writing data and disk Error Correction Codes to the disk; and (iii) a control means which (a) in the case where a read command is sent from the central device, operates the head to read from the disk, the data and disk Error Correction Codes, and sends to the central device the data and a portion of the disk Error Correction Codes consisting of the same number of bytes as the central device Error Correction Codes; and (b) in the case where a write command is sent from the central device, operates the head to write to the disk, the data and disk Error Correction Codes being sent from the central device.
2. The magnetic disk apparatus according to claim 1 In which the central device Error Correction Code consists of 4 bytes, and disk Error Correction Code consists of 7 bytes.
3. The magnetic disk apparatus according to claim 1 wherein the control means has a communicating function with the central device for receiving the central device Error Correction Codes therefrom and returning the same thereto.
1-1, 1 1
4. The magnetic disk apparatus according to claim 1 wherein the central device is a host computer.
5. The magnetic disk apparatus according to claim 1 wherein the control means is connected to the central device via a Hard Disk Controller.
6. The magnetic disk apparatus according to claim 2 wherein In the case where a write command Is sent from the central device, the disk Error Correction Code written on the disk consists of 7 bytes.
7. The magnetic disk apparatus according to claim 2 wherein in the case the disk Error Correction Code is read out from the disk according to the read command, the disk Error Correction Code Is reformed to 4 bytes.
8. The magnetic disk apparatus according to claim 7 wherein a 4 byte section from the beginning of the disk Error Correction Code is transmitted to the central device.
9. The magnetic disk apparatus according to claim 5 in which the hard disk controller is compatible with one of 4 byte, 6 byte, and 7 byte data.
10. A magnetic disk apparatus suitable for connection with a central device, the central device having central device Error Correction Codes consisting of a predetermined number of bytes, the magnetic disk apparatus comprising: (1) a disk on which is written:
(a) data; (b) disk Error Correction Codes for correcting errors in the data, consisting of "K" bytes, greater than the predetermined "L" bytes of the central device Error Correction Code; 4 k, (i:L) a head for reading data and disk Error Correction Codes from the disk, and for writing data and disk Error Correction Codes to the disk; and (iii) a control means which (a) in the case where a read command is sent from the central device, operates the head to read from the disk, the data and disk Error Correction Codes, and sends to the central device the data and the disk Error Correction Codes of "W bytes extracted from "K" bytes; and (b) in the case where a write command is sent from the central device, operates the head to write to the disk, the data and disk Error Correction Codes being sent from the central device, and disk Error Correction Codes for "K-L" bytes are added.
11. The magnetic disk apparatus according to claim 10 in which the central device Error Correction Code byte number "L" consists of 4 bytes, and disk Error Correction Code byte number consists of 7 bytes.
12. The magnetic disk apparatus according to claim 10 in which the disk Error Correction Code of "K-L" bytes added remains on the disk.
13. The magnetic disk apparatus according to claim 10 wherein the control means operates the head to write the disk Error Correction Codes of "K-W' bytes after the data and disk Error Correction Codes of "L" bytes sent from the central device to the data field of the disk.
14. The magnetic disk apparatus substantially as herein described with reference to and as shown in the accompanying drawings.
Published 1991 at The Patent Office. State House. 66171 HwbHolbom. LondonlAIC1 R 41P. Further copies may be obtained from --- -- C a nwiuim. ienuanw;-;in4j&-. ruruier copies yocoDtaincairom
GB9015902A 1989-07-20 1990-07-19 Disk drive/host computer interfacing Withdrawn GB2234098A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1188336A JPH0352166A (en) 1989-07-20 1989-07-20 Magnetic disk device

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GB9015902D0 GB9015902D0 (en) 1990-09-05
GB2234098A true GB2234098A (en) 1991-01-23

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GB9015902A Withdrawn GB2234098A (en) 1989-07-20 1990-07-19 Disk drive/host computer interfacing

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DE (1) DE4023196A1 (en)
GB (1) GB2234098A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2301997A (en) * 1995-06-08 1996-12-18 Hewlett Packard Co Computer graphics fits 40 bit word onto 32 bit bus

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0264602A2 (en) * 1986-10-20 1988-04-27 International Business Machines Corporation Fixed time gap format variable field length data transfer

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU622626B2 (en) * 1987-06-03 1992-04-16 Sony Corporation Method of processing data

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0264602A2 (en) * 1986-10-20 1988-04-27 International Business Machines Corporation Fixed time gap format variable field length data transfer

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2301997A (en) * 1995-06-08 1996-12-18 Hewlett Packard Co Computer graphics fits 40 bit word onto 32 bit bus
US5671373A (en) * 1995-06-08 1997-09-23 Hewlett-Packard Company Data bus protocol for computer graphics system
GB2301997B (en) * 1995-06-08 2000-02-23 Hewlett Packard Co Data bus protocol for computer graphics system

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Publication number Publication date
JPH0352166A (en) 1991-03-06
DE4023196A1 (en) 1991-01-31
GB9015902D0 (en) 1990-09-05

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