Data recorder

Abstract: A data recorder (1) includes a recording unit (6, 9, 13) for recording data having a predetermined data format and a frame address in a recording medium in units of frames each consisting of predetermined amount of data, and for forming a plurality of PARTITIONS each consisting of a plurality of data areas in which different types of data are recorded during recording. The data recorder (1) performs initialization of a length at least one of the PARTITIONS.

Description: This invention relates to data recorders for recording and reproducing data sent from, for example a computer and using, for example, a rotary head type digital audio tape recorder (DAT). In a computer, in order to protect (back-up) data written on a hard disc or the like, these data are transferred to and recorded in a data streamer (data recorder) once a day. As the data recorder, a 1/4-inch data cartridge type data recorder is often used. However, such a data recorder consumes a large amount of a magnetic tape, and has a low data rate in a recording mode. Therefore, the transfer/recording operation is time consuming. Moreover, as the data recorder cannot perform a high-speed search operation, it takes a long time to search for a starting portion of a desired data. A digital audio tape recorder of a helical scan type using a rotary head which has been recently become commercially available, a so-called DAT, can be used as a data recorder. When a DAT is used as the data recorder, data from the host computer is converted into data having a DAT format, and is then recorded. In the DAT format, two oblique tracks formed during one revolution of two heads having different azimuth angles comprise one frame, and 16-bit pulse code modulated (PCM) audio data are divided into halves to provide two 8-bit data, which are interleaved and recorded in units of frames. In addition, sub-data are recorded. In this case, as will be described later, a main area for recording PCM data and a sub-area for recording sub-data are formed on each track. Figure 1 shows a tape format when a DAT is used as a data recorder. Referring to Figure 1, a magnetic tape 17 consists of a magnetic body portion having a total length LO (tape length), and transparent leader tape portions 17a and 17b which are connected to respective ends of the magnetic body portion. A leading end of the magnetic body portion is called a BOM (Beginning Of Media), and its trailing end is called an EOM (End of Media). An EOT (End Of Tape) representing a pre-end is located at a position distant from the EOM towards the BOM by a length of 12. A point located at a position distant from the BOM by a length of 11 is called a BOT (Beginning Of Tape). A variety of data to be described later are recorded after the BOT. An area from the BOM to the BOT is called a device area 17c. The device area 17c is kept blank, or a signal for testing an apparatus is recorded in and reproduced from the device area 17c. When a head is located on the device area 17c, a tape cassette is attached/detached, or the tape 17 is loaded or unloaded. Note that the length 11 is, for example, 11 = 350 ± 10 mm and that the length 12 is, for example, 12 = 500 mm ( 2045 frames). A reference area 17d of 35 frames follows the device area 17c to record therein a signal representing the starting portion of data. A system area 17e of 115 frames follows the reference area 17d to record therein history such as the number of read and write operations, the number of errors and the like. The system area 17e is followed by an area of 23 frames called a vendor group 17f which can record therein desired data. The vendor group 17f is followed by a group area 17g in which there is recorded back-up data sent from a host computer. The group area 17g includes a plurality of groups each having 23 frames. Next to the group area 17g, an EOD (End Of Data) signal is recorded in 300 frames so that, upon reproduction, any data found to be recorded after the EOD are ignored as old data. An area from the BOM to the system area 17e is called a lead-in-area, and an area including the vendor group 17f and the group 17g is called a data area. When the DAT is employed as the data recorder and data are recorded and reproduced according to the above-mentioned format, a table of contents must be recorded in the tape 17 in order to now types and positions of data sent from the host computer and recorded in the tape 17. The contents of table include, for example, a data file name, date on which data is formed, the name of a person who forms the data, brief contents of data and data address. An area in which the contents of table are recorded is called a directory area. The directory area of desired length is recorded in a proper position next to the BOT or recorded just before the EOD shown in Figure 1 according to a predetermined data format. In this case, however, a special data format for the directory area must be provided, which necessarily requires the software and hardware of the system to be modified considerably. Moreover, a special command signal must be formed to make access between a central processing unit (CPU) and the system. In addition, when the directory area is provided just before the EOD, then it takes a long time to read the directory area after the tape cassette has been loaded on the DAT. Furthermore, there is a possibility that, during data recording, directory data recorded will be inadvertently erased by a malfunction or the like. European Patent Application No. EP-A-0 386 362 (published after the filing date of the present application) discloses a digital data storage apparatus in which data is stored on a tape medium in at least two different longitudinally-spaced sections. A predetermined format of data recordal includes tape-usage information recorded in a system log upstream of the main data area. Aggregated tape usage information can also be recorded in the system log of the first tape section. European Patent Application No. EP-A-0 327 201 on which the preamble of claim 1 is based discloses a data recording technique in which data frames each include a first area for recording main data and a second area for recording sub data. High speed search is facilitated by the use of recorded count signals identifying types of data segmentation units each comprising a plurality of frames. According to the present invention there is provided a data recorder comprising: recording means for recording data having a predetermined data format and a frame address on a recording medium in units of frames each consisting of a predetermined amount of data, and for forming a plurality of sections on the recording medium each consisting of a plurality of data areas in which different types of data are recorded during recording; characterised by: means for receiving information concerning the amount of data for recording in one of said sections for indicating the required data capacity of said one section during an initialization operation; means for determining the length of said one section from the received information concerning the required data capacity of said one section and also including capacity for operational margins arising from operational requirements of the data recorder; and means for recording a signal representing the length of at least said one section in a predetermined data area. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: Figure 1 is a schematic diagram showing a tape format of a previously proposed data recorder; Figure 2 is a block diagram showing an arrangement of a digital tape recorder, and to which the present invention can be advantageously applied; Figure 3 is a schematic diagram showing a data format of a digital tape recorder; Figure 4 is a schematic diagram showing a data format of a main data block; Figures 5A and 5B are schematic diagrams showing data blocks of a sub-code block; Figure 6 is a schematic diagram of a data format of a pack of the sub-code block; Figure 7 is a schematic diagram showing a tape format of a data recorder according to the present invention; Figures 8A to 8C are schematic diagrams of a tape format, and to which reference will be made in explaining the changes in the tape format when data are rewritten or added; Figure 9 is a flow chart to which reference will be made in explaining the steps involved in executing initialization of PARTITION 1; and Figure 10 is a flow chart to which reference will be made in explaining the steps involved in recording directory data in the PARTITION 1 Figure 2 illustrates an arrangement of a digital audio tape recorder (DAT) 1 to which the present invention can be advantageously applied. There is shown an interface bus line 2, a host computer 3 and inner bus lines 4 and 5. The DAT 1 mainly comprises a recording/reproducing section 6, a recording amplifier 7, a playback amplifier 8, a signal processing circuit 9, a random access memory (RAM) 10, a data controller 11, an interface board 12, a system controller 13, and a servo and motor drive circuit 14. The system controller 13, the signal processing circuit 9 and the data controller 11 are arranged such that they may exchange predetermined signals, such as an absolute frame number AFNO (to be explained later), between one another. The recording/reproducing section 6 is provided with a rotary head drum (not shown). A magnetic tape is wound around the rotary head drum over an angular extent of about 90 degrees and is transported by a capstan. The rotary head drum is provided with two recording heads A and B having different azimuth angles, and two reproducing heads A' and B' having different azimuth angles. During one revolution of the drum, the signal is recorded on the tape as two oblique tracks by the recording heads A and B, and the recording signal is reproduced from the tape by the reproducing heads A' and B'. Digital data supplied from the host computer 3 through the bus lines 5, 2 and 4 are inputted to the interface board 12, and are then processed by the data controller 11, the RAM 10 and the signal processing circuit 9 in a predetermined manner in accordance with the commands from the system controller 13. In this manner, the digital data are converted to the above-mentioned DAT format. The converted signal is supplied to the recording/reproducing section 6 through the recording amplifier 7, and is then recorded on the magnetic tape by the recording heads A and B. The signal recorded on the magnetic tape is reproduced by the reproducing heads A' and B'. The reproduced signal is supplied through the playback amplifier 8 to the signal processing circuit 9. Digital data, which results from re-converting the reproduced signal by the signal processing circuit 9, are supplied to the host computer 3 through the data controller 11, the interface board 12 and the bus lines 4, 2 and 5. In the above-mentioned apparatus, the DAT format on the magnetic tape is represented as shown in Figure 3. In Figure 3, it will be seen that, during one revolution of the recording heads A and B, two oblique tracks TA and TB are formed on the tape 17 as though coming from the underside of the drawing sheet, as indicated by an arrow a. The two tracks TA and TB constitute one frame. The track TA (or TB) consist of 196 blocks, and one block consists of 288 bits. 34 blocks at each end portion serve as a sub-area, and 128 central blocks serve as a main area. Each sub-area is further divided to provide, from the lower end of the track, a margin section, a phase locked loop (PLL) preamble section of a sub-code, a first sub-code section, a postamble section, a gap section between adjacent blocks, an automatic track following (ATF) signal section, a gap section between adjacent blocks, a PLL preamble section of data, a gap section between adjacent blocks, an ATF signal section, a gap section between adjacent blocks, a PLL preamble section of a sub-code, a second sub-code section, a postamble section, and a margin section. Each of the first and second sub-code sections is constituted by eight blocks, and other blocks are constituted by a predetermined number of blocks, respectively. Note that in Figure 3, the measure of lengths of sections is not accurate. The main area consists of 128 data blocks. As shown in Figure 4, each block is constituted by an 8-bit sync. (synchronizing) signal, an 8-bit PCM-ID (W1), an 8-bit block address (W2) and an 8-bit parity, and main data are stored in the following 256-bit section. The main data are 16-bit PCM data for L (Left) and R (Right) channels when an audio signal is processed. The 16-bit main data are divided to provide two 8-bit main data which are interleaved in the main areas of the oblique tracks TA and TB (one frame) together with the parity. When the DAT is used as a data recorder, the data sent from the host computer 3 are processed as the main data in the same fashion. These data are formatted as shown in Figure 4, and are recorded in the one-frame main area. Data formats in the first and second sub-code sections in the sub-area of Figure 3 will now be described. Each of the first and second sub-code sections consists of eight sub-code blocks, and can record 2048-bit data. Figures 5A and 5B show a data format of each sub-code block. After the 8-bit sync. signal, W1 and W2 sections, and parity are stored, and 256-bit sub-code data including a parity are stored. The sub-code data consists of four packs, each consisting of 8 x 8 bits (eight symbols). The blocks having EVEN and ODD block addresses have different contents of W1 and W2. Pack numbers (1 to 7) are provided over the EVEN and ODD blocks, as shown in Figure 5. An eighth pack is provided with a C1 code for error detection. The W1 section of the EVEN block consists of a 4-bit area ID and a 4-bit data ID, and the W2 section thereof consists of an upper (more significant) one bit "1", a 3-bit pack ID, and a 4-bit block address. The W1 section in the ODD block consists of a 4-bit undefined portion, and a 4-bit format ID, and the W2 section thereof consists of an upper one bit "1", a 3-bit all "0" code, and a 4-bit block address. Of the 3-bit all "0" code, and a 4-bit block address. Of the 3-bit all "0" code, the lowest (least significant) one bit is used as PRT-ID representing a partition number. Each of packs "1" to "7" is divided into eight words in units of eight bits. Each word includes, together with a parity, various codes such as a code indicating a lead-in area of a recording start portion on a tape, a code indicating a lead-out area of a recording end portion, a code indicating a recording data, an absolute frame number AFNO, a logical frame number, and the like. Figure 6 shows a format of the pack "3" of the even block. As shown in Figure 6, the pack "3" consists of eight 8-bit words PC1 to PC8. The upper four bits of the word PC1 are assigned to a pack number (in this case, "0011" indicating the pack "3"). The lower four bits of the word PC1 are assigned to an area-ID indicating each area to be described later in Figure 7. The absolute frame number AFNO is represented by a total of 24 bits of the words PC2, PC3 and PC4. The AFNO is a successive number assigned to all frames recorded on a roll of tape. An AFNO.MAX which represents the number of frames constituting the PARTITION to be described later by the AFNO is provided by a total of 24 bits of the words PC5, PC6 and PC7. The word PC8 has a parity with respect to the words PC1 to PC7. Figure 7 shows a tape format when a directory area is provided and introduces a concept called "PARTITION". PARTITION 1 and PARTITION 0 are provided next to the device area 17c. A data format of each of the PARTITIONS 1 and 0 is the same as the data format from the BOT to the end of the EOM in Figure 1. Reference numerals 17d to 17g in Figure 1 correspond to reference numerals 17d1 to 17g1 and 17d0 to 17g0 in Figure 7. The PARTITION 1 is used as the directory area. Directory data are recorded in the group section 17g1, and the same data as in the sections 17d to 17g in Figure 1 are recorded in the sections 17d0 to 17g0 of the PARTITION 0. Therefore, the beginning of each of the PARTITIONS 1 and 0 is the BOT. A length 13 of the PARTITION 1 serving as the directory area can be arbitrarily determined by initialization. Within the length 13, the directory data to be recorded in the group section 17g1 can be freely rewritten and added as shown in Figures 8A, 8B and 8C. That is, data recorded in two groups of the group section 17g1 as shown in Figure 8A can be rewritten or added in four or five groups as shown in Figure 8B or 8C. The PARTITION number representing the PARTITION 1 or 0 is recorded as a 1-bit PRT-ID as shown in Figure 5B. The AFNO.MAX which represents the number of frames corresponding to the initialized length 13 as a maximum value of the absolute frame number AFNO is recorded in the words PC5, PC6 and PC7 of 24 bits as shown in Figure 6. The AFNO.MAX is recorded in the system area 17el of the PARTITION 1. A method of determining the length 13 of the PARTITION 1 will be described below. The length 13 is determined in accordance with an amount of data written in the areas 17g1. The amount of data is designated by, for example, the host computer. The length 13 is actually given by the following equation (1) as the number of frames F corresponding to the length 13: F = R + S + V + G [k.U (1 + α) (1 + β)] + B + E In the equation (1), R is the length, in frames, of the reference area (in the present case, 35 frames), S is the length, in frames, of the system area (in the present case, 115 frames), and V is the length, in frames, of the vendor group I in the present case, 23 frames). G is the group number which results from dividing data A, instructed by the host computer, by data amount (in the present case, 125.6kB) of one group with the remainder raised. B is the length, in frames, of EOD (in the present case, 300 frames), and E is the length, in frames, between EOT and EOM (in the present case, 2045 frames). k is the multiple when data are written a plurality of times. That is, in a data recorder, the same data are sometimes successively written in a plurality of frames in order safely to protect the data. In this case, k changes into 2, 3, ..., n in accordance with whether the data are to be written twice, three times, ..., n times. U is the frame number of one group (in the present case, 23 frames). α is called a read after write margin. When the DAT is used as a data recorder, immediately after data are recorded in one frame upon recording, the frame is read back to check whether the recorded data are correct. For this reason, four rotary heads arranged at intervals of, for example, 90 degrees are used. If an error is detected in the recorded data, the same data are immediately recorded in another frame and data recording then continues in sequence from that point. In this case, the frame or frame written to the tape while the read-back data was checked for errors become useless. Thus α represents a total number of useless frames of one tape and is given as follows: α = (l + 1) x P/(1 + P) where 1 is the number of frames which are rendered useless upon an error of data recorded in one frame being detected and the frame being rewritten, numeral 1 of l + 1 represents the one frame in which an error of the data is found, and P is the generation rate of data errors in one tape. In the equation (1), β is called a margin for pause. In a data recorder, if a transfer speed of data sent from the host computer to the data recorder is lower than a recording speed of the data, data is sometimes not present in a buffer memory. In this case, the data recorder is caused to pause until data are stored in the buffer memory. When data are stored, the pause is released, and the data are recorded. In this case, several frames become useless after the pause is released and before the data are actually written. The β represents a total number of useless frames in one tape and is given by the following equation (3); β = (m x b)/(N x T) where m is the number of pauses generated in one tape, b is the number of frames which become useless in one pause release, N is the rotational speeds of the heads A and B, and T is the duration of one tape. In the above equation (1), when the host computer requests a data amount of A = 1 MkB, the length 13 of the PARTITION 1, that is the number of frames F is calculated as follows. In this case, G becomes 8 (1000/125.6 8), and assume that the data are to be written twice (k = 2), and that in the equation (2), 1 = 1 and P = 1%. In addition, assume that in the equation (3), m = 2,000, b = 35, N = 2,000 r.p.m., and T = 120 min. Therefore: Therefore: In this manner, the number of frames F of the PARTITION 1 is determined as F = 3023, and the initialization is effected in accordance with the flow chart of Figure 9. In Figure 9, in step ST-1, a tape is rewound to the BOM and then advanced by the length of the device area and stopped at the BOT. Then, the AFNO.MAX is obtained in accordance with the designated number of frames F. In the embodiment shown in Figure 7, the number of frames F corresponding to the length 13 of the PARTITION 1 is the AFNO.MAX. In step ST-2, the PARTITION 1 is designated to start recording from the reference area 17d1. During this recording, in step ST-3, the AFNO of each frame is monitored, thereby detecting the end of recording in the reference area 17d1. If the recording in the reference area 17d1 is ended, in step ST-4, the PARTITION 1 and the AFNO.MAX are designated, and then recording is performed in the system area 17el. Then, in step ST-5, the AFNO is monitored. If recording in the system area 17el is ended, the PARTITION 1 is designated in step ST-6, and then the vendor group and the group area formed of at least 23 amble frames are recorded. If recording of the vendor group and the group area has ended, the PARTITION 1 is designated in step ST-7, and then the EOD is recorded in the AFNO.MAX in step ST-8. If AFNO = AFNO.MAX in step ST-9, the next PARTITION 0 is designated and recording is performed in the reference area 17d0 in step ST-10. Then, in the step ST-11, the AFNO is monitored, and the end of recording in the reference area 17d0 is detected, thereby finishing the routine. After the above-mentioned steps are performed as a routine required for initialization, recording in the system area 17e0 of the PARTITION 0 may be subsequently performed. When initialization is performed as described above, no directory data is recorded in the group section 17g0, and therefore the group section 17g0 is not formed. An operation for recording the directory data in the group section 17gl after initialization has been performed will be described below with reference to a flow chart forming Figure 10. Referring to Figure 10, following the START of operation, in decision step ST-21, it is determined whether or not a current position of a tape is present at the PARTITION 1. If a YES is outputted in step ST-21, the flow proceeds to step ST-23. If on the other hand a NO is an answer in step ST-21, then the flow proceeds to the next step ST-22 to designate the PARTITION 1 and then advances to step ST-23. In step ST-23, the directory data is written in the group section 17gl in units of groups of 23 frames, and the EOD is written in 300 frames, thereby completing the operation. While recording is performed in step ST-23, the AFNO is monitored. Alternatively, the directory data may be recorded in the PARTITION 1 of a tape in which initialization has been performed by other data recorder. In this case, the tape speeds of data recorders are different (for example, in a range of ± 0.5%) so that EOM is determined to be a value smaller than AFNO.MAX by 1 %, that is AFNO.MAX (1 - 0.01). If AFNO.MAX (1 - 0.01) is obtained, this is acknowledged, and the recording operation is stopped. If AFNO.MAX (1 - 0.01) - 2045 is obtained before the EOM, then data indicating the presence of EOT are supplied to the host computer. Thus, regardless of the difference in the tape speeds of the data recorders, data recorded in the PARTITION 0 can be prevented from being erased while data are recorded in the PARTITION 1. In order to perform recording in the PARTITION 0, the current position of the tape is checked as in the operation of Figure 10. After the tape is positioned at the PARTITION 0, appropriate data are written in the system area 17e0. The, data from the host computer are written in the group section 17g0 in units of groups, and the EOD is written in 300 frames, thereby completing the operation. In order to reproduce the data recorded in the PARTITION 1 or 0, the current position of the tape is checked, and then data recorded in the desired PARTITION are reproduced in units of groups. In the above embodiment, two PARTITIONS 1 and 0 are formed. However, three or more PARTITIONS may be formed. In this case, n independent PARTITIONS can be formed in one tape so as to be accessed independently from each other. In addition, the PRT-ID in Figure 5 requires two or more bits. It is a matter of course that the directory area need not be formed. In the embodiment shown in Figure 7, since the directory area is formed at the start position of the tape, the directory data can be read out immediately after a tape cassette has been mounted. Since the directory area has completely the same data format as that of the PARTITION 0, the directory area and the PARTITION 0 can be accessed by normal hardware and software. Therefore, the system design is little changed. In addition, the directory data are not inadvertently erased during recording. Furthermore, the length 13 (number of frames F) can be freely determined during initialization, and data can be freely rewritten or added within the range of 13. After a tape cassette has been mounted, the system area 17el of the directory area is read. In this case, the AFNO.MAX corresponding to 13 is recorded in the system area 17el. Therefore, by monitoring the AFNO.MAX, data can be rewritten or added within the range of 13 without departing from this range. That is, a special signal for detecting whether the data falls outside the range of 13 is not necessary.

Claims: A data recorder (1) comprising: recording means (6, 9, 13) for recording data having a predetermined data format and a frame address (AFNO) on a recording medium (17) in units of frames each consisting of a predetermined amount of data, and for forming a plurality of sections (PARTITION 1,0) on the recording medium (17) each consisting of a plurality of data areas in which different types of data are recorded during recording; characterised by: means (9, 13) for receiving information concerning the amount of data for recording in one of said sections (PARTITION 1) for indicating the required data capacity of said one section (PARTITION 1) during an initialization operation; means (9, 13) for determining the length (F) of said one section (PARTITION 1) from the received information concerning the required data capacity of said one section (PARTITION 1) and also including capacity for operational margins arising from operational requirements of the data recorder (1); and means (6) for recording a signal (AFNO-MAX) representing the length of at least said one section (PARTITION 1) in a predetermined data area (PK3). A recorder (1) according to claim 1, wherein data representing a table of contents of data to be recorded in another of said plurality of sections (PARTITION 0) are recorded in said one section (PARTITION 1). A recorder (1) according to claim 2, wherein said one section (PARTITION 1) in which the table of contents is recorded is arranged at the start position of said recording medium (17). A recorder (1) according to claim 1, claim 2 or claim 3, wherein one of the operational margins used for determining the length of said one section (PARTITION 1) is a read after write margin (α) representing the total number of useless frames written to the recording medium (17) during checking of read-back data for errors if an error is detected. A recorder (1) according to claim 1, claim 2 or claim 3, wherein one of the operational margins used in determining the length of said one section (PARTITION 1) is a margin for pauses (β) representing the total number of useless frames arising from the recorder (1) being caused to pause to allow sufficient data to be stored in a buffer memory for subsequent recording on the recording medium (17). A recorder (1) according to claim 4 and claim 5, wherein said means (9, 13) for determining the length of said one section (PARTITION 1) is based on G [k.U (1 + α) (1 + β)] where G is the group number which results from dividing data A by the data amount of one group with the remainder raised, k is the multiple when data are written a plurality of times, U is the frame number of one group, α is the read after write margin and β is the margin for pauses. A recorder (1) according to claim 6,wherein α equals (l + 1) x P/(1 + P), where 1 is the number of frames which are rendered useless upon a data error recorded in one frame being detected and the frame rewritten, and P is the generation rate of data errors in one tape, and β equals (m x b)/ (N x T), where m is the number of pauses generated in one tape, b is the number of frames which become useless in one pause release, N is the rotation speed of recording heads, and T is the duration of one tape.

Inventors: BRAMHALL PETER, INAZAWA YOSHIZUMI, ODAKA KENTARO, OZAKI SHINYA, YAMADA MASAKI, BRAMHALL, PETER, INAZAWA, YOSHIZUMI, ODAKA, KENTARO, OZAKI, SHINYA, YAMADA, MASAKI
Applicants: HEWLETT PACKARD LTD, SONY CORP, HEWLETT-PACKARD LIMITED, SONY CORPORATION
Application year: 1989
Main classification: G11B20
IPC codes: G11B20, G11B27