GB Patent 1554641 - DATA-RECORDING DEVICE

Description

PATENT SPECIFICATION

( 1 1) ( 21) Application No 33188/76 ( 22) Filed 10 Aug 1976 C ( 31) Convention Application No's 50/097348 ( 32) Filed 11 Aug 1975 50/158628 26 Dec 1975 in Japan (JP)

Complete Specification Published 24 Oct 1979

INT CL 2 G 11 B 5/00 5/55 5/004 5/012 // 27/10 Index at Acceptance G 5 R B 13 B 24 B 264 B 3 OX B 30 Y B 311 B 31 B 321 B 333 B 340 B 342 B 345 B 34 Y B 352 B 361 B 36 Y B 444 B 451 B 452 B 45 X B 583 B 58 Y B 601 B 6 OX B 623 B 65 Y B 75 X B 75 Y B 762 B 76 Y B 784 B 87 B 88 ( 72) Inventor: Toshio KASHIO ( 54) "DATA-RECORDING DEVICE" ( 71) We, CASIO COMPUTER COMPANY LIMITED, a Japanese corporation, of 6-1, 2-chome, Nishishinjuku, Shinjuku-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to a data-recording device in which a magnetic head scans, without a break, a plurality of tracks on a rotatable magnetic recording medium, such as magnetic disc or magnetic drum, one after another, thereby to read data from the tracks or write data on to the tracks.

In a known data-recording device a plurality of tracks are concentrically provided on a recording medium, such as a magnetic disc, and data is written onto each track on the recording medium An index is given to a particular position on each track of the recording medium and the index point constitutes data write/read starting and ending positons for that track ln this casea magnetic head is shifted,by the trackdesignation information etc, to a desired position on the track of the recording medium and when the index Point of anv designated magnetic head to be shifted from the first track to the second track, when the magnetic head is in a condition in which it can read out the data on the second track, there sometimes occurs the case where the index point on the second track of the rotating magnetic madium has already passed the located position of the magnetic head and the readout operation must be delayed until the index point on the second track is again moved to the position where the magnetic head is located That is, when the magnetic head is shifted from one track to another, a dwell time is required for the index point on the other track to be rotated to the position where the magnetic head is positioned.

In another known data-recording device, check data are recorded at the read-write start position of each track of a rotatable magnetic recording medium The check data are, for example, the serial number of the track and a file number indicating what kind of data are recorded on the track From each track a magnetic head reads first the check data and then, if the data recorded on the remaining part of the track are found to be necessary scans the remaining part to read the necessary data.

R in r t hi olpe Ahor 1 1 olrio, JA ERRATUM S Pl CIFICATION NO 1554641 Page 11, line 75, insert HULSE & Co.

THE PATENT OFFICE 18 December 1979 " ( 33) &n ( 44) ( 51) ( 52) 1 554 641 Bas 73001/9 ( 21) Application No 33188/76 " ( 31) II" II) ( 33) ( 44) ( 51) ( 52) ( 1 1) ( 22) Filed 10 Aug 1976 Convention Application No's 50/097348 ( 32) Filed 1 1 Aug 1975 (IS 50/158628 26 Dec 1975 in Japan (JP) Complete Specification Published 24 Oct 1979

INT CL 2 GI 1 B 5/00 5/55 5/004 5/012 1/ 27/10 Index at Acceptance G 5 R B 13 B 24 B 264 B 3 OX B 30 Y B 311 B 31 Y B 321 B 333 B 340 B 342 B 345 B 34 Y B 352 B 361 B 36 Y B 444 B 451 B 452 B 45 X B 583 B 58 Y B 601 B 6 OX B 623 B 65 Y B 75 X B 75 Y B 762 B 76 Y B 784 B 87 B 88 ( 72) Inventor: Toshio KASHIO ( 54) "DATA-RECORDING DEVICE" ( 71) We, CASIO COMPUTER COMPANY LIMITED, a Japanese corporation, of 6-1, 2-chome, Nishishinjuku, Shinjuku-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, the method by which it is to be performed, to be particularly described in and by the following statement: -

This invention relates to a data-recording device in which a magnetic head scans, without a break, a plurality of tracks on a rotatable magnetic recording medium, such as magnetic disc or magnetic drum, one after another, thereby to read data from the tracks or write data on to the tracks.

In a known data-recording device a plurality of tracks are concentrically provided on a recording medium, such as a magnetic disc, and data is written onto each track on the recording medium An index is given to a particular position on each track of the recording medium and the index point constitutes data writelread starting and ending positons for that track In this casea magnetic head is shifted,by the track designation information etc, to a desired position on the track of the recording medium and when the index point of any designated track of the rotating recording medium confronts the magnet head a write-in or readout operation is started at the index point of the designated track of the recording medium.

Suppose now that after the readout of data on a first track data on a second track is sequentially read out When in this case the data readout is effected up to the index point on the first track, a seek instruction for shifting the magnetic head to the second track is issued to the magnetic head so as to shift the magnetic head from the first track to the second track.

Since, however, some time is required for the magnetic head to be shifted from the first track to the second track, when the magnetic head is in a condition in which it can read out the data on the second track, there sometimes occurs the case where the index point on the second 45 track of the rotating magnetic madium has already passed the located position of the magnetic head and the readout operation must be delayed until the index point on the second track is again moved to the position where the 50 magnetic head is located That is, when the magnetic head is shifted from one track to another, a dwell time is required for the index point on the other track to be rotated to the position where the magnetic head is positioned 55 In another known data-recording device, check data are recorded at the read-write start position of each track of a rotatable magnetic recording medium The check data are, for example, the serial number of the track and a 60 file number indicating what kind of data are recorded on the track From each track a magnetic head reads first the check data and then, if the data recorded on the remaining part of the track are found to be necessary scans 65 the remaining part to read the necessary data.

Since the check data occupies a considerable part of each track, it takes some time until the magnetic head starts reading the necessary data.

For this reason, the known data-recording 70 device is not so practical.

It is accordingly the object of this invention to provide a data-recording device which permits a magnetic head to be continuously scanned over a plurality of tracks without 75 involving any substantial dwell time.

According to this invention there is provided a data-recording device comprising a rotatable magnetic recording medium having a plurality of adjacent tracks, a magnetic head facing the 80 PATENT SPECIFICATION

1 554 641 2 1 554 641 recording surface of the recording medium for scanning the tracks to read data from the tracks or write data onto the tracks, means for moving the magnetic head to select the track to be scanned thereby, and means for detecting the read-write start position of each track, wherein the read-write start positions of any two immediately adjacent tracks are not on the same radius of the recording medium and are positioned such that the read-write start positions of said two tracks are spaced from one another by an angle of rotation larger than that angle through which the rotatable recording medium is rotated while the magnetic head is shifted from one track to an immediately adjacent track.

Preferably each track on the magnetic recording medium is provided with a reference position index mark, the index marks being radially aligned with one another; the full length of each track of the recording medium is divided, starting from said reference position index mark, into a plurality of sectors each of the same angular extent, the start and end positions of each sector defining with the center of the recording medium an angle greater than the angle through which the recording medium is rotated while the magnetic head is shifted from one track to an immediately adjacent track; and the means for detecting the read-write start position of each track is constituted by a counter which, in response to a first pulse generated every time the reference position index mark of the track being scanned passes the magnetic head, starts counting second pulses generated as the start positions of the sectors of the track being scanned pass the magnetic head during each rotation of the recording medium, and circuit means which compares the count of the counter with a number indicating the read-write start position of the track to be scanned by the magnetic head.

This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:Figure 1 is a plan view schematically showing one form of a magnetic recording medium; Figure 2 is a block circuit diagram according to one embodiment of this invention which controls a data write-in and readout operation; Figure 3 shows a relation between a track designation code configuration and sector check code configuration as used in the block circuit diagram; Figure 4 shows a relation between a track designation code configuration and a sector check code configuration as used in another embodiment of this invention; Figure 5 is a detailed circuit arrangement showing part of the block diagram of Figure 2; Figure 6 shows a data storage state used in another embodiment of this invention; Figure 7 shows a schematic view showing a data storage state on a plurality of tracks on a magnetic recording medium; Figure 8 is a block circuit diagram, corresponding to another embodiment of this 70 invention, which is adapted to control data write-in and readout operations; Figure 9 is a detailed circuit diagram corresponding to the embodiment of Figure 8; Figures IOA to 101 show signal waveform 75 diagrams for explaining the operation of the embodiment of Figure 9; and Figure 11 is a detailed circuit diagram showing a data processing device of Figure 8.

There will now be described by reference 80 to the appended drawings a data-recording device according to an embodiment of this invention.

Figure 1 shows a disk 11 used as a rotatable magnetic recording medium The disk 11 has a 85 plurality of circular tracks 13 a, 13 b, 13 c, 13 d concentrically arranged about the rotating shaft 12 Such tracks 13 a, 13 b, 13 c, 13 d are provided to a total number of 406.

The respective tracks of the disk 11 have an 90 index mark I formed by, for example, drilling so as to indicate a position from which a specified rotation angle is defined optically, magnetically or mechanically With the position of the index I taken as an initial or track start 95 ing position, the respective tracks of the disk 11 are separated into a plurality of equal divisions or sectors at a prescribed circumferential angular interval Like the index I, a plurality of sectorstarting positions SP are provided The spaces 100 or sectors between every adjacent pair of sectorstarting positions SP are designated as IS, 25, 3 S, 4 S as shown in Figure 1 Generally, each track has 32 sectors and in consequence 3 1 sector-starting positions in addition to the 105 initial posiion I Writing and reading of data is effected through a magnetic head (not shown) by rotating the disk 11 in the direction of an arrow indicated in Figure 1 With the first track 1 3 a, the position of the index I is taken as a 110 point at which recording of data is to be started and terminated Now let it be assumed that the disk 11 makes a rotation through a circumferential angular interval corresponding to less than one sector while the magnetic head is 115 shifted from the first track 1 3 a to the second track 13 b and further keeps on rotating Then the track starting position of the second track 13 b is set at the first sector-storing position SP.

Where the magnetic head is operated until the 120 index I taken as the terminal point of recording in the first track 13 a and the magnetic head is immediately shifted to the second track 13 b, then data is written in or read out of the second track 13 b without any waste of time after data 125 is fully written in or read out of the first track 13 a Thus throughout the tracks, writing or reading can be carried out continuously.

Figure 2 is a block circuit diagram of a device, where data is written in or read out of 130 1 554 641 1 554 641 the disk 11 With a disk recording device 14 including the magnetic head (not shown), signals showing the detection of the index I and a sector-starting position SP are read out of a detector 15 The magnetic head is operated by a magnetic head driving mechanism 16 so as to be selectively shifted from one track to another The magnetic head-driving mechanism 16 is controlled by an instruction issued from a control circuit 17 Upon receipt of an instruction from a central processing unit (abbreviated as "CPU") 18, the control circuit 17 sends forth instruction to change tracks and commence writing and reading.

A buffer memory 19 is provided for the CPU.

Data read out of the buffer memory 19 is supplied to the disk recording device 14 through a data bus 20 and AND circuit 21.

Data read out of the disk recording device 14 is stored in the buffer memory 19 through the data bus 20 A write instruction from the control circuit 17 is conducted as a gate signal to the AND circuit 21, and a read instruction from the control circuit 17 is supplied similarly as a gate signal to another AND circuit 22.

A signal showing the detection of the index I which is sent forth from the detector 15 is transmitted as a reset instruction to a first counter 23 This counter 23 is advanced in counting upon receipt of a signal showing the detection of a sector-starting position SP which is read out of the detector 15 The first counter 23 counts the sectors scanned by the magnetic head, and its count shows which sector is currently scanned by the magnetic head A count made by the first counter 23 is transmitted to a first coincidence circuit 24 An output from a first buffer memory 25 stored with an instruction for designating a track in which data from the CPU 18 is to be written or an instruction for specifying a track out of which stored data is to be read is supplied to the first coincidence circuit 24 as data to be compared with a count made by the first counter 23 Where coincidence takes place between the output from the first buffer memory 25 and the count made by the first counter 23, then the first coincidence circuit 24 produces a coincidence signal.

Where the disk 11 is assumed to have 406 tracks as previously mentioned, then a trackspecifying instruction is formed of nine bits.

Where each track is supposed to have thirtytwo sectors, then a signal SP denoting a sector order number from the Index is formed of five bits The first counter 23 produces a count of bits to be compared with the least significant bits of the above-mentioned 9-bit data in the coincidence detector 24 In Figure 3 the sequential positions IT, 2 T, 3 T occupied by the respective tracks are represented by 9-bit coded data given opposite thereto With the above-mentioned disk recorder 14, a track starting position is shifted by one sector, that is, one circumferential angular interval to record data, each time the magnetic head changes from one track to the immediately adjacent one.

The track staring position of, for example, the first track IT is the start of sector IS represented by a five-bit code of ( 00000) The track starting 70 position of said track 2 T is the start of sector 2 S represented by a five-bit code of ( 00001).

Similarly, the track starting position of said track 3 T is denoted as 3 S As apparent from Figure 3, a look at the last five bits of nine 75 bits constituting track-specifying data indicates the above-mentioned starting position of the respective tracks For example, where the second track 2 T is specified and coincidence takes place between a count of ( 00001) of the 80 detected sector starting position SP made by the first counter 23 and the last five bits of ( 00001) of the 9-bit code specifying said second track 2 T, then the read-write start position of the second track 2 T is determined 85 Referring to Figure 2, where the coincidence detector 24 issues a signal showing coincidence between a count made by the first counter 23 to indicate the sector at which the read-write start position of a specified track is located and 90 the last five bits of a 9-bit code denoting said specified track which is stored in the first buffer memory 25, then the magnetic head in the disk recorder 14 is brought exactly to a position at which the read-write of said specified 95 track starts The above-mentioned coincidence signal is supplied as a reset signal to the second counter 26 Signals showing the detection of the index I and the sector starting positions SP which have been delivered from the 100 detector 1 5 are supplied as count-advancing signals to the second counter 26 through an OR circuit 27 Thus, the second counter 26 makes a count corresponding to an amount of rotation angle of the disk recorder 11 as measured from 105 the starting position of the read-write of a specified track A count made by the second counter 26 is compared in a second coincidence detector 29 with data on the sequential order of a sector specified for a read-write 110 operation which has been supplied from the CPU 18 Where coincidence takes place between the above-mentioned count and data, then a signal denoting said coincidence is supplied to an AND circuit 30 115 An instruction to reposition the magnetic head which has been given by the control circuit 17 is conducted to a counter 31 for counting the counts corresponding to the sequential order of the sectors of a specified 120 track Upon receipt of the instruction to reposition the magnetic head, the counter 31 counts the counts corresponding to the sequential order of the sectors of the track on which the magnetic head then lies A count 125 denoting the sequential order of said track which has been made by the counter 31 is compared in a third coincidence detector 32 with data stored in the first buffer memory 25 which shows the sequential order of the 130 1 554 641 specified track Where coincidence arises between the track specified by the CPU 18 and the track on which the magnetic head is disposed, then the coincidence detector 32 produces a signal denoting said coincidence.

This coincidence signal is supplied as a gating instruction to the AND circuit 30 An output from the AND circuit 30 is sent forth as a gate signal to the AND circuits 21, 22 and also as an instruction to commence reading or writing of data to the control circuit 1 7 This control circuit 17 supplies the CPU 18 with an instruction to commence reading or writing of data in accordance with the following program.

Where, with a data-recording device arranged as described above, data transferred through the data bus 20 is written in the disk recorder 14, then the CPU 18 supplies said disk recorder 14 with signals denoting the sequential order of a specified track of the disk recorder 14 and also the sequential order of a sector of said track in which writing is to be started These two signals are stored in the first and second buffer memories 25, 28 respectively The control circuit 17 issues a writing instruction to drive the disk recorder 14 When the disk recorder 14 rotates the disk, signals denoting the index l and the starting position of the readwrite of the specified track are read out At this time, the counter 31 makes a count corresponding to the sequential order of a track scanned by the magnetic head When a track specified by the CPU 18 is scanned by the magnetic head, the third coincidence detector 32 produces a coincidence signal Where the starting position SP of the sector at which the readwrite of a specified track starts is detected, while said specified track is being scanned by the magnetic head, then a coincidence signal is issued from the coincidence detector 24 which compares a count made by the first counter 23 and a data stored in the first buffer memory 25.

This coincidence signal resets the second counter 26 The second counter 26 freshly counts a number of sector starting positions SP as measured from the start of the sector at which the read-write of a specified track starts, thereby determining the sequential order of a specified sector in said specified track Where coincidence takes place between the counts corresponding to the sequential order of said specified sector and data supplied from the CPU 18 to the second buffer memory 28 which denotes the sequential order of said specified sector, then the second coincidence detector 29 generates a coincidence signal Upon receipt of a sector coincidence signal from the second coincidence detector 29 and a track coincidence signal from the coincidence detector 32, the AND circuit 30 sends forth an output This output is supplied to one imput of the AND circuit 21 which is also supplied with a writing instruction delivered from the control circuit 17 Data read out of the buffer memory 19 is written in a specified sector of a specified track of the disk recorder 14 through the data bus 20 and AND circuit 21 Thus, data is written into the sector whose sequential order has been specified by the CPU 18 starting at the starting position SP.

Reading of data out of the disk recorder 14 is effected by causing the control circuit 1 7 to give a reading instruction, and supplying the first and second buffer memories 25, 28 with signals denoting the sequential order of a track specified for reading and the sequential order of a specified sector of said specified track Data read out of the disk recorder 14 is stored in the buffer memory 19 through the AND circuit 22 and data bus 20.

The foregoing description refers to the case where the magnetic head was shifted from a given track to the adjacent one in a shorter time than that which was required for the disk in the disk recorder 14 to be rotated through one circumferential angular interval corresponding to one sector of said given track Where, however, the disk recorder 14 is rotated through a circumferential angular interval corresponding to more than one sector but less than two sectors of a track and further keeps on rotating, beyond the starting position SP of the first sector of a given track, then it is necessary to delay the time required for the start position SP of the sector at which the read-write of said given track starts to reach the magnetic head by a length of time which the disk takes for rotation through two sectors.

With the first track 1 T, the start of sector 1 S is taken as the position in which the read-write of that track is to be commenced The start of sector 3 S is taken as the position in which the read-write of the second track 2 T is to be commenced The start of sector 5 S is taken as the position in which the read-write of the third track 3 T is to be commenced Figure 4 shows 5-bit codes denoting specified tracks and 5-bit sector-positioning codes representing the specified sectors of said specified tracks The specified sectors IS, 3 S, SS of the respective tracks IT, 2 T, 3 T are formed of 5-bit codes.

The respective sequential orders IS, 35, 55, 7 S of the specified sectors are denoted respectively by a 5-bit code of 00000, 00010, Where coincidence is obtained between the last four bits of the track-specifying codes and the first four bits of the representing the sector-specifying codes, then it is possible 1554641 to confirm the sequential orders of the specified tracks and the track starting position of said specified tracks.

According to the data-recording device of this invention, shown in F gure 2, the first coincidence detector 24 detects coincidence between the first four bits of a 5-bit count made by the first counter 23 and the last four bits of 9-bit track-specifying data read out of the first buffer memory 25 and produces a coincidence signal, provided the lowermost bit of account made by the first counter 23 is 0.

Namely, the data-recording device of this invention shown in Figure 2 should have such an arrangement as indicated in Figure 5, where the disk is rotated through a circumferential angular interval corresponding to more than one sector but less than two sectors during a track changing period Referring to Figure 5, the first counter 23 is formed of five binary counters BC arranged in series, and supplied with a signal showing the detection of the index I as a reset pulse and also with a signal showing the detection of the starting position SP of the first sector as a count-advancing pulse.

Further, the first counter 23 is so designed as to issue a count signal formed of five parallel bits.

The first buffer memory 25 comprises nine memory elements for storing 9-bit coded data delivered from the CPU 18 The nine bits constituting said data are read out of the nine memory elements in parallel.

The coincidence detector 24 comprises an inverter 35, OR circuit 33 and four exclusive OR circuits 34 a to 34 d The first four bits of a count signal supplied form the first counter 23 are supplied to the four exclusive OR circuits 34 a to 34 d respectively The last four bits of data read out of the buffer memory 25 are also conducted to said OR circuits 34 a to 34 d in the same order as the above-mentioned first four bits Where coincidence takes place between the above-mentioned first and last groups of four bits, then the exclusive OR circuits 34 a to so 34 d all produce an output having a logic level of " O " Output signals from the exclusive OR circuits 34 a to 34 d and the lowermost bit of a count signal supplied from the first counter 23 are carried to the OR circuit 33, an output from which is transmitted to the inverter 35.

Where the lowermost bit of a count signal read out of the first counter 23 is " O " and the first four bits of said count signal coincide with the last four bits of the track data code then the first coincidence detector 24 issues a coincidence signal.

Where the first coincidence detector 24 of Figure 2 has such an arrangement as shown in Figure 5, then it is possible to write data in the disk recorder 14 or read it out therefrom in such a manner that the point of time at which the starting position of the first sector of a given track reaches the magnetic head is delayed by 70 a length of time required for the disk to be rotated through a circumferential angular interval corresponding to two sectors, each time the magnetic head is shifted from said given track to the adjacent one 75 Where it is necessary to delay the point of time at which the starting position of the sector at which the read-write of a given track starts reaches a magnetic head by a length of time required for the disk to be rotated through a 80 circumferential angular interval corresponding to three or more sectors, each time the magnetic head is shifted from said given track to the adjacent one, then the coincidence detector 24 85 of Figure 5 is also applicable with required modifications.

The foregoing description refers to the embodiment wherein a plurality of tracks provided in a magnetic disk are each separated 90 into a plurality of divisions or sectors by the index I and the plurality of sector-starting positions SP, and the starting positions of the sectors at which the read-write of the respective 95 tracks start are set at the index position and the specified ones of said sector-starting positions.

In some cases, however, each track of the magnetic disk is provided with an individual index mark at which the read-write is to be 100commenced, and further, if necessary, with check data for indicating the form of data stored in the track, thereby controlling the writing of data in the track and reading it out 105 therefrom Where the check data is read out of a plurality of tracks by means of a magnetic head, the aim is to find whether a given track contains an index mark with the check data within one full rotation of said track Where 110 absence of the index data is confirmed, the magnetic head is immediately shifted to each succeeding track, without taking the trouble of reading out all the data stored in said index 115 free track, thereby enabling the required data to be read out of a plurality of tracks without wasting time.

There will now be described by reference to Figures 6 to 11 a data-recording device 120 according to another embodiment of this invention This embodiment enables the magnetic head to seek the starting position of a sector preceded by an index without wasting 125 time while being shifted from one track to another Figure 6 only shows the first and second tracks TI, T 2 of a rotatable magnetic recording medium, for example, a magnetic disk An index II is bored at a given point on 130 I 1 554 641 the first track Ti An initial data ID for indicating the commencement of data reading is written behind a small blank space provided after the index 11 The initial data ID is formed of three consecutive character codes each represented by a 4-bit code of " 0000 " Reading of three " O "-bit codes corresponding to three characters shows the presence of the initial data ID A track head TH is written behind the initial data ID The track head TH is formed of a combination of coded numerical data whose foremost bit is represented by " 1 " According to the embodiment of Figure 6, the track head is formed of two digits, for example, " 5 " Each of the three 4-bit initial codes constituting the initial data 1 D consists of a series of " O " bits as previously described Other data are formed of code arrangements shown in the following table.

Table I Code Arrangement Data 4-bit code 0 1111 1 1110 2 1101 3 1100 4 1011 1010 9 (dot) 0101 Initial code 0000 Data TNO showing the sequential order of, for example, the first track Tl is written immediately behind the track head TH The initial data ID, track head TH and track number TNO jointly represented a first check data.

A second initial data ID having the same code arrangement of ZZZ as described above is written after the first index 11 Written after said second initial data ID is a data head DH showing that specific data follows said data head DH This data head DH is formed of a combination of a plurality of coded numerical data, for example, " 50 ", whose foremost bit indicates " 1 " A file number FNO showing the content of each item included in specific data is written after the data head DH Written after the file number FNO is the content of each item The aforesaid second initial data ID, data head DH and file number FNO jointly constitute a second check data.

With the second track T 2, too, an index 12, the starting position of the read-write of said second track T 2, is followed by first and second check datas The index 12 is positioned at a 70 point corresponding to a prescribed circumferential angular interval through which the disk is rotated from the index 11 of the first track TI in the specified direction Now let it 75 be assumed that a magnetic head is shifted, upon receipt of a reposition instruction, to the second track T 2 in a direction indicated by an arrow Sl shown in Figure 6 Then, the second index 12 is set at a point facing the foremost 80 end of said arrow Si After the second check data written in the first track TI is read out, a reposition instruction is given As the result, the magnetic head is shifted to the second track 85 T 2 to scan its surface The initial data ID forming the foremost part of the first check data and the following data are read out in succession Successively, the magnetic head is brought to the starting position of the read-write 90 on each succeeding track, which movement of the magnetic head corresponds to a circumferential angular interval through which the disk is rotated while the magnetic head is 95 shifted from one track to another.

Where the disk has a plurality of tracks Tl, T 2, T 3, T 4, T 5 shown in Figure 7, the magnetic head is shifted along the line indicated by S The initial data ID and following check 100 data of each track are read out A coincidence detector detects whether the check data thus read out represents data common to a plurality of item data being read out of the tracks If 105 the check data thus read out is not the required common data, then the magnetic head is immediately shifted to another track adjacent to the preceding track which does not contain the desired common data, without taking the 110 trouble of searching for said common data throughout said preceding track, in order to seek out the desired common data in said another track 115 Figure 8 is a block circuit diagram of a device for carrying out the above-mentioned reading and writing of data A magnetic disk recorder 51 is controlled by an instruction issued from a central processing unit (CPU) 52 A track 120 specifying circuit 53 designates a track in which data is to be written or out of which data is to be read Data read out of the magnetic disk 51 is supplied to a waveform shaper 54 Where, 125 upon receipt of a reading instruction from the CPU 52, data represented by a logical code of " 1 " showing the presence of a significant signal is read out of the magnetic disk 51, then said data is conducted to the waveform shaper 54, 130 1 554 641 which in turn produces an output signal shaped into, for example, a rectangular waveform The above mentioned data represented by a logical code of "l" which has been read out of the waveform shaper 54 is supplied as a reset instruction to a counter 55 This counter 55 counts clock pulses issued from a clock pulse oscillator 56, for example, a quartz oscillator which generates stable standard clock pulses.

Each time an output of " 1 " is sent forth by the waveform shaper 54, the above-mentioned reset signal is used as a synchronizing signal for clock pulses issued from the clock pulse oscillator 56.

Now let it be assumed that a time interval between the respective bits constituting stored data corresponds to a length of time required for the clock pulse oscillator 56 to issue 20 clock pulses The 20-count counter 55 sends forth an output corresponding to an interbit time interval as a synchronizing signal to a character counter 57 per counting cycle, that is, each time, for example, " 9 " included in the " 20 " count is repeatedly counted The character counter 57 counts a number of bit outputs supplied from the 20-count counter 55 The character counter 57 is of a 4-count type, where one character data read out of the disk recorder 51 is formed of four bits Output signals successively delivered from the waveform shaper 54 are held one after another in a holding circuit 58, each time the 20-count counter 55 issues a bit-synchronizing signal represented by, for example, the above-mentioned count " 9 " An output from the holding circuit 58 is conducted to a data bus 59 and also to an initial data detector 60 a, a first check data detector 60 b for detecting a track head and a second check data detector 60 c for detecting a data head, all constituting a data-detecting circuit 60.

An output detection signal from the initial data detector 60 a is held in the holding circuit 6 a and also supplied to a gate circuit 62 together with an output from the holding so circuit 58 Both signals are supplied to the 4-scale character counter 57 as a reset instruction signal to define an initial numeral from which the 4-scale character counter 57 commences digit counting, in order to effect the synchronization of said digit counting While the digit counting of the 4-scale character counter 57 is being synchronized, output count signals from the 4-scale character counter 57 are read out in parallel as counts indicating bits constituting a character A count signal issued from the 4-scale character counter 57 which represents the last digit of said 4-scale is supplied to the datadetecting circuit 60 as a signal for controlling the detection of a character data read out of the disk recorder 51.

An output from the holding circuit 61 is delivered as an input signal to one input of an AND circuit 63, the other input of which is supplied with an output from the detector 60 b 70 of the first check data 1 An output from the AND circuit 63 is transmitted as track head data to the CPU 52 Also the output from the holding circuit 61 is delivered as an input signal 75 to one input of an AND circuit 64 the other input of which is supplied with an output from the detector 60 c of the second check data 11.

An output from the AND circuit 64 is sent forth as a signal denoting the data head to the 80 CPU 52.

Data being written in the disk recorder 51 is transferred through the data bus 59 and AND circuit 65 A writing instruction from the CPU 85 52 and count signals from the 4-scale character counter 57 are supplied as gate signals to the gates of AND circuit 65 When the gates of said AND circuit 65 are opened, the count signals from the 4-scale character counter 57 are 90 supplied to the disk recorder 51.

Figure 9 is a more concrete representation of the above-mentioned data-recording device The waveform shaper 54 comprises an AND 95 circuit 66 supplied with data read out of the disk recorder 51, OR circuit 67 for drawing out an output from said AND circuit 66, and AND circuit 68 for feeding back an output from said OR circuit 67 A reading instruction from the 100 CPU 52 is supplied as a gate signal to one input of the AND circuit 66.

The holding circuit 58 comprises an OR circuit 69 supplied with an output from the OR 105 circuit 67 included in the waveform shaper 54; a delay circuit 70 formed of a delayed flip-flop circuit supplied with an output from the OR circuit 69 and operated by clock pulses 01, 02 issued from the clock pulse oscillator 56; an 110 AND circuit 71 for feeding an output from the delay circuit 70 back to the OR circuit 69; and an inverter 72 connected to one gate of the AND circuit 71 and supplied with an output from the counter 55 when it repeatedly counts, 115 for example, " 9 " included in the 20-scale.

Outputs from the waveform shaper 54 are supplied one after another to the holding circuit 58, each time the counter 55 counts " 9 " 120 The AND circuit 68 is opened or closed according to an output from the inverter 73 connected to the output terminal of the delay circuit 70.

When data of "I" is read out of the disk recorder 51 while data of " O " is held in the 125 holding circuit 58, then the waveform shaper 54 latches said data of "I " Under this condition.

data of " 1 " is supplied to the holding circuit 58 130 1 554641 An output from the counter 55 which denotes a count " 9 " is supplied to the holding circuit as a synchronizing signal when bit data is read out of the disk recorder 51 The " 9 " output from the counter 55 is also transmitted to an AND circuit 74 together with a clock pulse k 1 issued from the clock pulse oscillator.

An output from the AND circuit 74 is used as a bit synchronizing pulse Ob This synchronizing pulse Bb from the AND circuit 74 is supplied as a counting instruction to the 4-scale counter 57 and also sent forth to an AND circuit 75 together with an output denoting the count " 3 " constituting the last digit of the 4-scale of the counter 57 As the result, the AND circuit produces a digit pulse AD for reading out a character of 4-bit arrangement A bitsynchronizing pulse O Bb delivered from the AND circuit 74 is supplied, together with a clock pulse 02, as an instruction for shifting data stored in a memory section 76 consisting of three 1-bit memory elements arranged in series.

The first memory element of the memory section 76 is supplied with data stored in the holding circuit 58 through an AND circuit 77 which is opened by a reading instruction.

An output from the holding circuit 58 and outputs from the three memory elements of the memory section 76 are transferred to lines 59 a to 59 d constituting the data bus 59 respectively.

Outputs are read out in parallel from said lines 59 a to 59 d to provide a 4-bit character.

Signals transferred to the four lines 59 a to 59 d of the data bus 59 and read out of the holding circuit 58 and memory section 76 are supplied to the memory section 78 of the data detecting circuit 60 The memory section 78 comprises four 1-bit memory elements corresponding to the above-mentioned four lines 59 a to 59 d The memory section 78 is operated by a clock pulse 02 issued from the clock pulse oscillator 56 as well as by an output from the 4-scale counter 57 which denotes the last digit of the 4-scale, that is, a clock pulse AD issued for each character Thus, data transferred to the data bus 59 is detected by a decoder 79 at a time delayed by a length of time required for one character to be read out.

Data supplied to the data bus 59 is detected by a decoder 80 The former decoder 79 detects data "Z( 0000)" constituting an initial code and a numeral " 5 ( 1010)" The latter decoder 80 detects an initial code "Z( 0000)", a numeral " 0 ( 1111)", and a point " ( 0101)" An output signal from the decoder 79 which shows the detection of the initial code Z is supplied to a delay circuit 81 operated by the clock pulse AD and clock pulse 02 An output from said delay circuit 81 is conducted to one input of an AND gate 82, which concurrently acts as a circuit for detecting the initial data Z Where the other inputs of the AND circuit 82 simultaneously receive a synchronizing pulse AD for reading a character from the AND circuit 75, 70 and initial codes Z from the decoders 79, 80, namely, where initial codes corresponding to three characters are produced, then an initial data is issued from the AND circuit 82 When 75 the inputs of an AND circuit 83 receive data on a numeral " 5 " from the decoder 79 and a data on a point " " from the decoder 80 and also the synchronizing pulse OD, then the AND circuit 83 sends forth an output regarding the first 80 check data denoting the track head of " 5 ".

When the inputs of an AND circuit 84 receive a data on a numeral " 5 " from the decoder 79 and a data on a numeral " O " and also the synchronizing pulse OD, then the AND circuit 85 84 generates an output regarding the second check data denoting the data head of " 50 ".

The AND circuits 82, 83, 84 concurrently act as the aforesaid data detectors 60 a, 60 b, 60 c 90 of Figure 8.

"Write" data transferred through the data bus 59 is read out through the AND circuits a to 65 d connected to the lines 59 a to 59 d 95 of the data bus 59 respectively, and then supplied to an AND circuit 65 f through an OR circuit 65 e The AND circuit 65 a is opened by a signal denoting the first digit " O " of a fourscale data read out of the four-scale character 100 counter 57 and is kept closed in the absence of said " O " signal Similarly, the AND circuits b, 65 c, 65 d are opened or closed upon receipt of or in the absence of the second, third and fourth digits " 1 ", " 2 " and " 3 " respectively 105 of said four-scale data of the four-scale character counter 57 As the result, bit data supplied in parallel to the lines 59 a to 59 d of the data bus 59 are now read out in series The AND circuit 110 the AND circuit 65 f sends forth "write" data the counter 55 which denotes a numeral of, for example, " 19 " Each time 20 clock pulses from the clock pulse oscillator 56 are counted, the AND circuit 65 f sends forth "write" data 115 to the disk recorder 51 while the reading of data bits is synchronized.

The gate circuit 62 for sending forth a presetting instruction to cause the four-scale counter 120 57 subsequently to start counting from " 1 " comprises a flip-flop circuit 85 which is set by an output from the AND circuit 82 of the initial data detector which denotes the detection of an initial data, an AND circuit 86, one input 125 of which receives a signal when the flip-flop circuit 85 is set and the other input of which is supplied with an output from the holding circuit 58 and which supplies the four-scale counter 57 130 1 554 641 with an instruction to cause said count 57 subsequently to start counting from " 1 -, and a delay circuit 87 which is operated by clock pulses 01, 02 and which delays an output from the AND circuit 86 by a length of time required for an initial data to be read out and supplies said delayed output as a ieset signal to the flipflop circuit 85 and causes the four-scale counter 57 to commence a synchronous counting upon receipt of a signal instructing of the reading of the digit " 1 " following the initial data.

There will now be described the writing of data in the disk of the data-recording device of this invention arranged as described above.

The 20-scale counter 55 counts clock pulses just as issued from the clock pulse oscillator 56 without specifying any digit of the 20-scale as the starting point of counting The 20-scale counter 55 generates an output, each time " 9 " and " 19 " are counted A " 9 " output from said counter 55 is supplied at an interval of one bit to the 4-scale character counter 57 through the AND circuit 74 as an instruction for upcounting of "+ 1 " Thus, a number of bits is counted for each character, while the reading of bits is synchronized Where, under this condition, a writing instruction is issued and data bit signals are transferred in parallel through the lines 59 a to 59 d of the data bus 59, then said data bit signals are converted into series-arranged data bit signals by passing through the AND circuits 65 a to 65 d and OR circuit 65 e.

Where " 19 " output from the 20-scale counter is supplied to the AND circuit 65 f, then the AND circuit 65 f sends forth "write" data to the disk recorder 51 with the reading of bits synchronized The disk recorder 51 detects a data on the sequential order of a specified track which follows the initial data, and delivers specific data following the data head to the data bus 59.

Desired data stored in the disk of the disk recorder 51 is read out through the process of causing the CPU 52 to generate a track-specifying output, defining the sequential order of the 0 specified track by the track-specifying circuit 53 and controlling the operation of the disk recorder 51 by said sequential order signal.

Where the disk recorder 51 is thus operated and the CPU 52 issues a reading instruction, then a magnetic head scans the surface of the specified track The detection of the initial data leads to the synchronization state and, by reading out the first data "I" from the disk, synchronization is achieved to permit data readout Each time -"I data is read out of the disk, the waveform shaper 54 produces an output to reset the 20-scale counter 55, thereby effecting the synchronization of bit reading An output from the waveform shaper 54 is conducted to the data bus 59 through the holding circuit 58 and AND circuit 77 Under this condition, however, the data detecting circuit 60 does not send forth an output to the CPU 52 At this time, 70 data is not yet read out because no preparation is made for said reading Where the index I stored in a given track of the disk recorder 51 passes through a point on the track facing a 75 magnetic head and a blank space on the track in which no data is stored and a coded signal ( 0000) is read out as an initial data corresponding to three characters, then reading of data bits from the holding circuit 58 is synchronized by 80 a bit-synchronizing signal from the counter 55.

Thereafter, a coded signal ( 0000) corresponding to the first character of the initial data is conducted through the AND gate 77 to the 85 data bus 59 and memory section 76 Data read out of the memory section 76 upon receipt of a clock pulse 02 from the clock pulse oscillator 56 is carried through the data bus lines 59 a to 59 d and supplied to the decoder 80 of the 90 data-detecting circuit 60 together with an output from the data bus 59 A signal ( 0000) corresponding to the first of the three characters ZZZ is delivered to one of the inputs of the 95 AND circuit 82 An initial data signal ( 0000) corresponding to the second character Z undergoes the same processing as described above after leaving the disk and passes through the data bus 59 to the memory section 78 of the 100 data detecting circuit 60 Upon receipt of a clock pulse 02 from the clock pulse oscillator 56, a stored initial data signal ( 0000) corresponding to the second character Z is read 105 out to the decoder 79 and is transmitted to the other input of the AND circuit 82 after being delayed from the initial coded signal corresponding to the first character Z by a length of time required for one character to be read 110 out An initial data signal ( 0000) corresponding to the last character Z is read out of the decoder 79 through the same process as mentioned above and supplied to the other 115 input of the AND circuit 82 through the delay circuit 81 after being delayed from an initial data signal corresponding to the immediately preceding character Z by a length of time required for one character to be read out Thus, 120 initial data signals ( 0000), ( 0000) ( 0000) corresponding to the three characters Z, Z, Z are sent forth from the AND circuit 82 upon receipt of the last synchronizing pulse OD from 125 the AND circuit 75 An output from the AND circuit 82 which shows the detection of the above-mentioned initial data signals is supplied as a set signal to the flip-flop circuit 85 included in the gate circuit 62 130 When the flip-flop circuit 85 is set, then a signal is supplied therefrom to AND circuit 86.

Thus, the character counter 57 is brought into a position waiting for the reading of all the bits constituting one character to be synchronized.

Where, under this condition, the first check data " 5 " is read out of the disk to indicate a track head, then the first bit " 1 " of a code representing said check data " 5 " is supplied to the holding circuit 58 through the waveform shaper 54 When the AND circuit 86 is supplied with the " 1 " bit signal held in the holding circuit 58, then the AND circuit 86 produces an output, which presets the four-scale counter 57 subsequently to commence counting from the digit " 1 " This process is intended to synchronize the reading of all the bits constituting one character Later when a " 1 " bit is read out of the disk, the waveform shaper 54 generates an output A signal showing the absence of an output which is read out of the disk is stored in the memory section 76 A track head and data head following the initial data are detected by the data-detecting circuit while the reading of all the bits constituting one character is synchronized by the 4-scale character counter 57 Specific data bits stored in the disk are read out in parallel from the data bus lines 59 a to 59 d A signal from the decoder 79 which denotes " 5 " and a signal from the decoder 80 which denotes " O " are detected by the AND circuit 84 as a data head A detection output from the AND circuit 84 is supplied to the CPU 52 Thus, reading of specific data is commenced While specific data is read out of the disk with the reading of all the bits constituting one character synchronized, the CPU 52 is supplied with a signal denoting the file number of an item included in the stored data, thereby determining by said file number whether the item being read out is the desired item Where noncoincidence takes place between the file number read out and the file number of the desired item, then a track-changing instruction is given to the track-specifying so circuit 53 to search for the file number of the required item.

Figure 10 is a detailed illustration of the wave-forms of signals produced at various sections of Figure 9 Now let it be assumed that the waveform shaper 54 and holding circuit 58 produce outputs having waveforms shown in Figures 1 OA and l OB respectively Then the 20-scale counter 55 produces an output having a waveform shown in Figure IOC when it counts " 9 " When counting " O " to " 3 ", the 4scale counter 57 sends forth outputs having waveforms shown in Figures IOD to 1 OG.

Upon completion of each counting cycle, the 4-scale counter 57 generates a pulse 01 D of Figure 1 OH for synchronizing the reading of all the bits constituting one character Upon receipt of said synchronizing pulse 1 AD, initial codes are read out of the decoder 79 and 70 delay circuit 81 When supplied with initial codes ( 0000), ( 0000), ( 0000) corresponding to three characters, the AND circuit 82 produces signals of Figure 10 I denoting the detection of 75 said initial codes.

There will now be described by reference to Figure 11 the operation of the CPU 52 which judges whether the content of data read out coincides with that of a specified data from a 80 check data showing the sequential order of a given track read out and a file number representing a data head read out Referring to Figure 11, the CPU 52 comprises a memory device 88 and control type CPU 89 Data is stored in the 85 memory device 88 through an AND circuit 90 which is opened upon receipt of an instruction from the control type CPU 89 The CPU 52 is further provided with memory units 91, 92 for 90 storing the sequential order of a track containing data and the file number of each item included in said data respectively Signals denoting the sequential order of the track and the file number of each time are supplied to AND circuits 93, 94 respectively The control type CPU 89 issues a gate signal to the AND circuits 93, 94 An output from a holding circuit 95 for holding an output from the data-detecting 100 circuit 60 which denotes the detection of a track head and an output from a holding circuit 96 for the holding a signal from said datadetecting circuit 60 which denotes the detection of a data head are delivered to the AND circuits 105 93, 94 respectively Outputs from the AND circuits 93,94 are supplied, together with specific data, to a coincidence detector 98 through an OR circuit 97 In said coincidence 110 detector 98, comparison is made between the track number TNO following the track head TH and the sequential order of a track stored in the memory 91 and also between the file number FNO following the data head DH and 115 the file number stored in the memory 92.

Where noncoincidence appears as the result of these comparisons, then an instruction to change tracks is given to the disk recorder 51 120 through a selection circuit 99, and, if necessary, an error signal is sent forth to the disk recorder 51 Where the above-mentioned comparisons indicate coincidence, the control type CPU 89 is supplied with a coincidence signal Then the 125 control type CPU 89 issues an instruction to the memory 88 to cause specific data from the data bus 59 to be supplied to said memory 88 through the AND gate 90 The control type 130 1 554 641 1 554641 CPU 89 issues a writing instruction to the disk recorder 51 and a reading instruction to the waveform shaper 54.

The foregoing description refers to the embodiment where the magnetic head was shifted from one track to another by detecting the second check data However, the magnetic head may be shifted as shown by the arrow 52 of Figure 6, after the track number TNO is read out.