JP4592280B2 - Data storage - Google Patents

Description

  The present invention relates to a data storage device capable of accurately storing and reading data counted continuously in a backup memory.

  For devices that need to store the operating time for life management, or devices that need to store the frequency of occurrence of some event, such as the number of switch operations, store count data such as the operating time and frequency of occurrence in the backup memory. It has been done. The stored data is read from the backup memory when the operation is restarted after the device stops operating, and the next count is started with the read value as an initial value. Therefore, the count data needs to be stored in the backup memory with high accuracy and read out with high accuracy.

  In a general storage memory, for example, an EEPROM or the like, access is performed in units of 1 byte. Therefore, when data of 2 bytes or more is stored, it is necessary to perform access several times. However, for example, if the power supply to the device is interrupted for some reason after storing 1 byte, data after the next byte cannot be stored. Therefore, if the stored value of the backup memory is read at the next power-on in such a state, an incorrect value may be read.

  FIG. 1 is a diagram showing a writing process and a reading process in the case of storing 2-byte data. Since the example of FIG. 1 assumes a case where a value of 0 to 255 is counted by a 16-bit machine, each bit takes 16 numerical values of 0 to 9 and A to F. “Processing cycle” in the figure indicates a write cycle for writing data from a microcomputer or the like to a backup memory, and “value to be stored” indicates a value that the microcomputer or the like counts and needs to be backed up. Furthermore, “write value” indicates data transmitted from the microcomputer or the like to the backup memory in each processing cycle, and “stored value” indicates a value stored in the backup memory.

  Now, as shown in the figure, when a numerical value of 5AFE is counted as a value to be stored in the microcomputer or the like, the upper byte value 5A of the numerical value is transmitted to the backup memory and written in the processing cycle 1. At this time, since the value 5AFD immediately before 5AFE is stored in the backup memory as the previous stored value, in the processing cycle 1, the numerical value 5A is overwritten in the area storing the upper byte of the backup memory. .

  In process cycle 2, the lower byte of the value 5AFE to be stored is written into the lower byte area of the backup memory. This completes the writing of the value 5AFE to be stored. By performing the same writing process, when the count-up progresses and the value to be stored reaches 5B00, the value 5B00 is written to the backup memory in the processing cycle 6.

  In the state where the count value is written according to the processing cycle of FIG. 1, when the operation of the device is terminated by the normal operation and the power is shut off, the backup memory is in a state where the value to be stored is completely written, That is, the state is maintained in the even cycle state of FIG. Therefore, when the next power supply to the device is turned on, correct numerical data can be read from the backup memory and used as the initial count value.

  However, if the power supply of the device is shut down in an abnormal way due to some reason, for example, if the power is shut down at the end of writing the upper byte of the value to be stored, the stored data at the next power on For reading, the data in the odd-numbered cycle state of FIG. 1 is read. For example, when the power is turned off at the end of the processing cycle 5, the upper byte 5B of the value 5B00 to be stored is written to the backup memory, while the lower byte of the value 5AFF to be stored last time is written in the lower byte. The FF is held.

  When the power is turned on again in this state, the value 5BFF stored in the backup memory in the processing cycle 5 is read out. Since the value that should be read out is the value 5B00 to be stored, a completely different value is read out. Thus, the read value when an abnormal power interruption occurs is an unreliable value.

  Conventionally, in order to cope with such a situation, when writing interruption occurs due to abnormal power interruption or the like during the writing process to the backup memory, the occurrence of the situation is stored, and the stored value at the time of reading is stored. I was taking measures such as forcibly clearing it.

  As a prior art related to the general technology of the present invention, Japanese Patent Application Laid-Open No. 2000-222290 discloses a technology for storing and holding data stored in a backup memory even when the power is turned off. In this technique, whether or not the power is turned off during data writing is stored by a flag.

  Further, Japanese Patent Laid-Open No. 6-162054 discloses a product inspection apparatus capable of efficiently performing inspection work without being affected by a failure such as a power shutdown, and Japanese Patent Laid-Open No. 6-83720 which discloses a data backup type computer system. Japanese Patent Laid-Open No. 6-12191 discloses a method for copying data between auxiliary storage devices after power is restored when the system is powered off.

JP 2000-222290 A

JP-A-6-162054

JP-A-6-83720

JP-A-6-12191

  As described above, conventionally, when an abnormal power interruption occurs during writing to the backup memory, the read value becomes unknown at the time of the next read, and thus measures such as forcibly clearing this are taken. However, with this method, all of the previous data is lost and a new count for life management must be started.

  The present invention has been made with respect to this point, and even when the writing process to the backup memory is forcibly interrupted, no special means for detecting and storing the occurrence of such a situation is required. In addition, the present invention was made for the purpose of obtaining a data storage device that can read stored data with a minimum error.

In order to solve the above problems, the data storage device of the present invention is written with a volatile memory that holds a value of 2 bytes or more that are continuously counted up or down as a value to be stored, and the value to be stored. In a data storage device comprising a backup memory, and a volatile memory and a data processing unit that controls data writing and reading in bytes between the backup memories, the backup memory stores the value to be stored in bytes. A byte storage area for storing, and a previous value area for storing the value of the byte position next to the least significant byte in the previous value of the value to be stored, wherein the data processing unit includes the value to be stored, the previous value, Is overwritten in the same area as the area stored during the previous storage process,
When writing data to the backup memory, write the previous value of the value to be stored in the previous value area, and then write the value to be stored in the byte position next to the least significant byte in the byte storage area. When performing processing to write to the least significant byte position in the byte storage area and reading the data from the backup memory, when the value of the least significant byte stored in the byte storage area in the backup memory is the final count value Adopts the value stored in the previous value area as the value of the byte position next to the least significant byte.

In order to solve the above-described problem, the data storage device of the present invention includes a volatile memory that holds a value of 2 bytes or more that are continuously counted up or down as a value to be stored, and a value to be stored. In a data storage device comprising: a backup memory to be written; and a data processing unit that controls writing and reading of data in units of bytes between the volatile memory and the backup memory, the backup memory stores the value to be stored in bytes A byte storage area for storing in units, and a previous value area for storing the value of the byte position next to the least significant byte in the previous value of the value to be stored, and the data processing unit includes the value to be stored and the previous value Value is overwritten in the same area as the area stored in the previous storage process. When writing data to the memory, the previous value of the value to be stored is written to the previous value area, and then the value to be stored is written to the least significant byte position in the byte storage area. When performing processing to write to the byte position next to the lower byte and reading data from the backup memory, the value of the least significant byte stored in the byte storage area in the backup memory is the count start value, and the byte When the value of the byte position next to the least significant byte in the storage area is the same as the value stored in the previous value area, the final count value is adopted as the value of the least significant byte.

  As can be seen from FIG. 1, when the read value of the backup memory is significantly different from the actual value, it occurs when the value of the least significant byte of the read value is FF, that is, the final value that can be counted. This is because if the value of the least significant byte is FF, the value at the next position of this byte is likely to be rewritten. Therefore, in the present invention, when writing data to the backup memory, the value at the position next to the least significant byte in the previous value of the value to be stored is similarly written in the previous value area of the backup memory. Thus, if the value of the least significant byte is FF at the time of reading, adopting the value written in the previous value area as the next value of the least significant byte minimizes the difference between the read value and the original value. can do.

Further, in the above device, the data processing unit is writing data based on the value of the least significant byte stored in the byte storage area and the value stored in the previous value area when reading data from the backup memory. The stored value of the backup memory in which an abnormal process may have occurred is corrected.

  In the above apparatus, the volatile memory includes a first area for storing the value to be stored and a second area for storing the previous value of the value to be stored, and the data processing unit is stored in the backup memory. In writing the value to be stored in bytes, the values in the first area and the second area are compared in bytes. If they are different, the value stored in the first area is stored in the backup memory. It is supposed to write.

  As a result, the number of write processes can be greatly reduced, so that the degree of freedom in designing the entire system is improved and the durability of the backup memory is improved.

  Further, in the above device, when the value to be stored is a value of 3 bytes or more, the previous value area includes all byte position values that are updated by updating the least significant byte value in the previous value. Is memorized. As a result, even if the value to be stored is 3 bytes or more, data can be read out with a minimum error range regardless of abnormal power interruption.

  Further, in the above apparatus, when the data processing unit rewrites data in the order from the lower byte to the upper byte in the backup memory, when reading the data from the backup memory, the least significant byte stored in the backup memory When the value is 00 and the previous value is equal to the value of the byte position next to the least significant byte, the last value that can be counted is used instead of the read value of the least significant byte (00). Yes. As a result, even in a device in which data is written to the backup memory in order from the lower byte to the upper byte, the data can be read with a minimum error range.

  FIG. 2 is a block diagram showing an embodiment of a data storage device according to the present invention. In the figure, reference numeral 1 denotes a main CPU such as a microcomputer having a data processing unit 2 and a memory 3 which is usually volatile. The data processing unit 2 processes data according to a program stored in advance in a ROM or the like, and the memory 3 stores numerical data counted up by a certain access time to the device, the number of switch operations, or the like. In the present embodiment, the memory 3 stores an area 31 for storing the upper byte value of the count data, an area 32 for storing the lower byte value, and an area 33 for storing the upper byte value of the previous count value (hereinafter referred to as the previous value). It has.

  Reference numeral 5 denotes an external memory for backup, and is composed of a nonvolatile memory such as an EEPROM. The backup memory 5 includes areas 51, 52, and 53 for storing the contents of the memory 3 through data communication 6 with the microcomputer 1.

  In the apparatus of FIG. 2, when the device is turned off, the data in the memory 3 is lost. Therefore, when the power of the device is turned on again, the data stored in the backup memory 5 is read, and the counting up of the operation time and the like is restarted based on the read value. When the contents of the memory 3 change due to counting up, the value is written in the backup memory 5. In this embodiment, since the data is a 2-byte value and it is necessary to store the upper byte value of the previous value, three processing cycles are required for writing and reading data.

  FIG. 3 is a diagram showing an operation flow when the apparatus shown in FIG. 2 is applied to life management of an electronic device or the like that is guaranteed to operate for a long time. In this apparatus, the operation time is managed by counting up 1 when the electronic apparatus operates for 10 minutes. First, when the microcomputer 1 starts operating by turning on the power of the electronic device (step S1), the data processing unit 2 performs a process of reading the storage contents of the backup memory 5 into the memory 3 (step S2). Details of this read processing will be described later with reference to FIG.

  When the reading process is completed, the timer is then started (step S3), and the operation time management is started. In step S4, it is determined whether or not the timer has passed 10 minutes. When 10 minutes have passed, the contents of the memory 3 are updated by 1 (step S5). At this time, the value in the area 33 storing the previous value is also updated to the upper byte value of the value before the update.

  Next, in step S6, the updated contents of the memory 3 are written into the backup memory 5 (step S6). After confirming that the power is not turned off in step S7 (NO in step S7), the timer further Monitor the next 10 minutes. If the power is off in step S7, the process ends.

  FIG. 4 is a diagram showing details of the read processing routine of FIG. First, when the device is turned on, the microcomputer 1 reads the contents of the backup memory 5 (step S10). If the lower byte value read at this time is FF (YES in step S11), the previous value read is read as the read value. The higher byte value is adopted (step S12), and the memory 3 is rewritten (step S13). On the other hand, if it is determined in step S11 that the value of the lower byte is not FF (NO in step S11), the read value is adopted as it is as the value of the memory 3 (step S13).

  FIG. 5 is a diagram showing the effect of the reading process shown in FIG. The items and numerical data in FIG. 5 are the same as those shown in FIG. 1 and will not be described repeatedly. However, “previous value to be stored” and “previous value” are the upper byte values in the previous value to be stored. Indicates. Further, “value to be stored” and “previous value to be stored” are values stored in the memory 3, “stored value” indicates a value stored in the backup memory 5, and “read value” is shown in FIG. The values read from the backup memory and written into the memory 3 in accordance with the processing procedure shown are shown.

  In the processing of this embodiment, since it is necessary to store the previous value of 1 byte for 2 bytes of data, writing and reading of one data requires three processing cycles.

  In the processing cycles 6 to 8 in FIG. 5, the value held in the area 52 of the backup memory 5 is FF. When the power is forcibly turned off during writing in cycle 9, the values 5A (region 53), 5B (region 51), and FF (region 52) that have been written in cycle 8 are stored in backup memory 5. Has been. According to the reading process shown in FIG. 4, since the lower byte value of the backup memory 5 is FF, the previous value 5A held in the area 53 is adopted as the upper byte value.

  As a result, the memory 3 of the microcomputer 1 is written with 5A as the previous value, 5A as the upper byte value, and FF as the lower byte value. Therefore, the microcomputer 1 resumes management of the operation time of the device using the numerical data 5AFF as the initial value. .

  FIG. 6 is a diagram showing a data storage device according to the second embodiment of the present invention. In the embodiment shown in FIG. 2, as shown in FIG. 5, all bytes are written when data is written to the backup memory 5, and the values are the same as the values stored in the memory 5. Will also be overwritten. In the second embodiment, when the written value and the value stored in the memory 5 are the same, the write process is skipped to reduce the processing cycle. By adopting such a processing method, the processing time in the microcomputer is somewhat increased, but the increase is much smaller than the writing time to the external memory, and as a result, the processing time is greatly shortened.

  As shown in FIG. 6, the apparatus according to the present embodiment includes a second memory 4 that stores a read value in the microcomputer 1 in order to omit unnecessary write cycles. Similar to the first memory 3, the second memory 4 has an area 43 for storing the previous value, an area 41 for storing the upper byte value, and an area 42 for storing the lower byte value. Note that when the power of the device is turned on, the contents of the backup memory 5 are written in the second memory 4 in the same manner as the first memory 3, but in the state where the operation continues, the first memory 3 Is written into the backup memory 5 or at the time of writing, the contents of the first memory are written into the second memory.

  FIG. 7 is a diagram showing details of the writing process (step S6 in FIG. 3) when the apparatus shown in FIG. 6 is used, and FIG. 8 is a diagram showing the effect in that case. The flowchart shown in FIG. 7 basically compares the value to be stored stored in the first memory 3 and the read value stored in the second memory in each byte, and only the value of the byte that has been changed. Is for performing write processing (update processing).

  Note that the contents of the first and second memories 3 and 4 are the same at the end of writing of the value to be stored last time, but after the next 10 minutes, the contents of the first memory 3 are not changed. In step S5, the value is counted up by 1, so that both values are different at the start of the writing process 6.

  The reading process in the present embodiment will be described with reference to FIG. 7. First, in step S20, the read value is compared with the previous value in the value to be stored. That is, the value stored in the area 33 in FIG. 6 is compared with the value stored in the area 43 to determine whether or not there is a change. If “YES” in the step S 20, it indicates that the previous value has been changed, and thus the value in the first memory area 33 is written in the backup memory 5 area 53. If NO in step S20, that is, if there is no change in the previous value, the writing process is skipped.

  Next, in step S22, it is determined whether or not the upper byte has been changed. If there is a change (YES in step S22), the value stored in the area 31 in the first memory is written in the area 51 of the backup memory 5. If there is no change (NO in step S22), the writing process is skipped. In step S24, it is determined whether or not there is a change in the lower byte. If there is a change (YES in step S24), the value in the first memory area 32 is written in the backup memory 5 area 52 in step S25. If there is no change (NO in step S24), the writing process is skipped.

  When the writing process is completed in this way, the value to be stored in the first memory 3 is written as the read value of the second memory 4 (step S26), and the writing process is completed. As a result, as shown in FIG. 8, processing cycles 3, 6, 8, 9 and 12 are necessary as the writing process, but other processing cycles can be omitted.

  In the first and second embodiments, the present invention is applied to operation time management of millimeter wave radar, but the present invention is not necessarily limited to such a case. For example, the present invention can be similarly applied to a device that needs to store the number of occurrences of some event.

  FIG. 9 is a diagram showing an operation flow when the present invention is applied to a device that needs to store the number of switch operations. In this embodiment, in step S30, a backup value reading process is performed in the same manner as in the first and second embodiments, and then it is determined whether or not a switch operation has been performed in step S31. When there is a switch operation (YES in step S31), the value to be stored is advanced by 1 in step S32, and a writing process is performed in the same manner as in the first and second embodiments (step S33).

  Thereafter, it is determined whether or not the power is turned off in step S34. If not (NO in step S34), the process returns to step S31 again to determine whether or not the switch is operated again. If NO in step S31, the process waits until there is a switch operation.

  Each of the above embodiments shows the case where the numerical value to be stored is composed of data of 2 bytes, but the present invention can be applied to the case of data of 3 bytes or more. In this case, by setting the value stored as the previous value to the value of the upper 2 bytes of the previous value to be stored, the data can be stored and read with higher accuracy.

  FIG. 10 shows the procedure of a 3-byte data write process. As is apparent from this figure, the value 01FFFF is held in the backup memory in the processing cycle 7, and therefore when the power is cut off in the middle of the processing cycle 8, in the conventional apparatus, reading from the backup memory is 01FFFF. It becomes. This is significantly different from the original value 010000 to be stored or the previous value 00FFFF.

  Therefore, in the present embodiment, as the previous value, the value of the upper 2 bytes of the previous value to be stored is stored, and when the value of the lowest byte is FF upon reading, the value of the upper 2 bytes read is replaced. By using the previous value, data reading errors are minimized. For example, when writing is completed in processing cycle 7 of FIG. 10, the previous value 00FF is used instead of the upper 2 bytes value 01FF at the time of reading, and the read value is set to 00FFFF, thereby minimizing the error from the actual value. It can be.

  Each of the above-described embodiments employs a writing method in which data is rewritten in order from the upper byte to the lower byte when rewriting data to the backup memory 5. Of course, it may be performed in order of the upper byte. An embodiment of the present invention in that case is shown below.

  FIG. 11 is a diagram showing a read processing routine when the data processing unit 2 of the microcomputer 1 shown in FIG. 6 performs memory write control in the order of the previous value, the lower byte value, and the upper byte value. 12 is a diagram for explaining the operation of the reading process shown in FIG. In the present embodiment, as shown in FIG. 11, when the device is turned on, the microcomputer 1 reads the contents of the backup memory 5 (step S40), and determines whether or not the read lower byte value is 00 in step S41. .

  As can be understood by referring to the processing cycle 8 in FIG. 12, when the value to be stored is 5B00 and the lower byte value 00 is written after the previous value 5A, the backup memory 5 stores the previous value. The value is 5A, the upper byte value is 5A, and the lower byte value is 00. Therefore, when the power is turned off during the processing cycle 9, in the conventional apparatus, the read value of the backup memory 6 when the power is turned on again becomes the memory state of the processing cycle 8, that is, 5A00, and the actual storage. A value that is significantly different from the desired value 5B00 and the value 5AFF of the processing cycle 7 is read out.

  In the present embodiment, in order to avoid such a situation, it is determined whether or not the lower byte value read in step S41 in FIG. If YES in step S41, it is determined in step S42 whether the upper byte value is the previous value. If YES in step S42, that is, if the upper byte value is the same as the previous value, in the next step S43, processing for replacing the lower byte value with FF is performed. With this process, at the end of the process cycle 8 in FIG. 12, the value 5AFF of the previous process cycle is read when reading when the power is turned on again.

  The value read in step S43 is written in the memory 3 as a value to be stored in step S44. As a result, instead of the value 5A00 stored in the processing cycle 8, the previous value 5AFF to be stored is written in the memory 3, and the data can be read with a minimum error.

  If NO in step S41, that is, if the value of the lower byte is not 00, there is no problem even if the value stored in the backup memory is read as it is, so that the read value is written in the memory 3 as a value to be stored in step S44. . Similarly, if NO in step S42, that is, even if the lower byte value of the read value is 00, if the upper byte value is different from the previous value, it indicates that the upper byte value has already been rewritten. Therefore, it is not inconvenient to adopt the read value as it is as a value to be stored. Therefore, this value is written in the memory 3 in step S44. In the case of NO at step S42, the state of the processing cycle 9 in FIG.

  In the present embodiment, since all the stored values of the memory are 00 (initial state) in the initial state of the device, when the device is operated for the first time, in the flow of FIG. The condition that “the previous value (00) is equal to the upper byte value (00)” is applied, and there arises a problem that the lower byte value starts from FF even though the apparatus is operated for the first time. Therefore, in the initial state of the apparatus, processing such as setting FF as the previous value of the memory or 01 as the lower byte value is necessary.

  Each of the above embodiments shows a case where the value to be stored is a value to be counted up. However, in the present invention, it is needless to say that the value to be stored may be a value to be counted down. When the value to be stored is a value to be counted down, in the memory in which rewriting is performed from the upper byte, when the lowest byte is 00 (that is, the final value that can be counted), the value stored in the previous value area is It can be read and used as the upper byte. In a memory that is rewritten from the lower byte, if the lower byte is FF (that is, the count start value) and the upper byte is the same as the previous value, the highest byte is used. What is necessary is just to employ | adopt 00 (namely, the last value which can be counted) to a low-order byte.

  In each of the above embodiments, when the possibility of abnormal termination during data writing is suspected from the count value stored in the backup memory and the previous value, the count value before counting up or before counting down is adopted as the read value. However, instead of this, the count value after counting up or after counting down may be adopted as the read value.

  As described above, according to the embodiments, according to the apparatus of the present invention, data can be read with a minimum error even when writing to the backup memory is forcibly interrupted. There is no need to clear the counting work that has been continued until then due to an abnormal power interruption as in the apparatus, and the continuous work can be performed.

The figure which uses for description of the conventional data storage method. 1 is a block diagram showing a data storage device according to a first embodiment of the present invention. The figure which shows the operation | movement flow of the apparatus shown in FIG. The figure which shows the detailed flow of the read-out process shown in FIG. The figure which shows the effect of the apparatus shown in FIG. The block diagram which shows the data storage device concerning the 2nd Embodiment of this invention. The figure which shows the detailed flow of the write-in process shown in FIG. The figure which shows the effect of the apparatus shown in FIG. The figure which shows the operation | movement flow of the apparatus concerning the 3rd Embodiment of this invention. The figure which uses for description of the 4th Embodiment of this invention. The figure which shows the read-out flow of the apparatus concerning the 5th Embodiment of this invention. The figure which shows the effect of embodiment shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Microcomputer 2 ... Data processing part 3 ... 1st memory 4 ... 2nd memory 5 ... Backup memory 31, 32, 33, 41, 42, 43, 51, 52, 53 ... Storage area

Claims (4)

A volatile memory that holds a value of 2 bytes or more that is continuously counted up or down as a value to be stored, a backup memory to which the value to be stored is written, and between the volatile memory and the backup memory In a data storage device comprising a data processing unit that controls data writing and reading in byte units,
The backup memory includes a byte storage area for storing the value to be stored in byte units, and a previous value area for storing a value of a byte position next to the least significant byte in the previous value of the value to be stored,
The data processing unit overwrites the same area as the area stored during the previous storage process with the value to be stored and the previous value.
When writing data to the backup memory, write the previous value of the value to be stored in the previous value area, and then write the value to be stored in the byte position next to the least significant byte in the byte storage area. Perform processing to write to the least significant byte position in the byte storage area,
When reading data from the backup memory, if the value of the least significant byte stored in the byte storage area in the backup memory is the final count value, the value of the byte position next to the least significant byte is set to the value. A data storage device employing a value stored in the previous value area. A volatile memory that holds a value of 2 bytes or more that is continuously counted up or down as a value to be stored, a backup memory to which the value to be stored is written, and between the volatile memory and the backup memory In a data storage device comprising a data processing unit that controls data writing and reading in byte units,
The backup memory includes a byte storage area for storing the value to be stored in byte units, and a previous value area for storing a value of a byte position next to the least significant byte in the previous value of the value to be stored,
The data processing unit overwrites the same area as the area stored during the previous storage process with the value to be stored and the previous value.
When writing data to the backup memory, write the previous value of the value to be stored in the previous value area, and then write the value to be stored in the least significant byte position in the byte storage area. Write to the byte position next to the least significant byte in
When reading data from the backup memory, the value of the least significant byte stored in the byte storage area in the backup memory is the count start value, and the value of the byte position next to the least significant byte in the byte storage area Is the same as the value stored in the previous value area, the final count value is adopted as the value of the least significant byte. 3. The data storage device according to claim 1, wherein the volatile memory includes a first area and a second area each having the byte storage area, and the data processing unit reads data from the backup memory. Sometimes, the value of the byte storage area read from the backup memory is stored in the byte storage area in the second area, and the value to be stored in the byte storage area of the backup memory is written in bytes. When the values of the first area and the second area are compared in byte units and the values are the same, the value stored in the first area is not written to the byte storage area of the backup memory. A data storage device.   3. The data storage device according to claim 1, wherein when the value to be stored is a value of 3 bytes or more, the value is updated in the previous value area by at least updating the least significant byte value in the previous value. A data storage device, characterized in that it stores the values of all byte positions to be processed.

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