JP2000071566A - Imaging apparatus and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus in which a data can be written correctly into a nonvolatile memory storing the aging of the apparatus even at the time of emergency without sacrifice of the convenience of a user even if the data is abnormal in worst case. SOLUTION: When door open is detected at S48 and power supply to the entire apparatus is interrupted at S50, a timing where writing is disabled due to voltage drop is waited before starting writing of a specified volume of data in an EEPROM. When turn off of power switch is detected at S40, a decision is made at S42 whether a data is being written in the EEPROM and if a data is not being written, a specified volume of data in the EEPROM at S44 before interrupting power supply at S46.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus equipped with a nonvolatile memory, a control method thereof, and a computer readable memory storing a control program therefor.

2. Description of the Related Art In an image forming apparatus, in particular, a full-color printer or the like, in order to obtain high-quality output without aging of the main body and replacement parts, or to avoid a situation in which a serious failure is caused, Some monitors the status of replacement parts. As a means for storing a state change of the apparatus main body or the replacement part from the time of production / shipment even after the power is turned off, there is an apparatus equipped with a nonvolatile memory. For example, to keep track of the life of the main unit,
The failure information before the power is turned off is stored.

As a nonvolatile memory used in such an apparatus, an EEPROM which can be easily connected at a low cost is used.
In general, such a memory device is used.
This memory device can be implemented with a simple configuration at low cost, but has the disadvantage that it takes time to write.
Therefore, it is not possible to neglect the possibility that the power will be turned off or be affected by noise during writing.If the power is turned off due to an accident or the data is garbled due to noise, etc.,
Accurate memory contents cannot be guaranteed.

[0003] These problems do not occur during normal operation, especially in a standby state. However, in an emergency (for example, when the power is turned off or when a part including the memory is replaced), writing to the memory can be performed in spite of the necessity of reliably backing up the device information in such a situation. Easy to be unstable.

Conventionally, errors have been detected using the checksum of the entire write data in order to guarantee the accuracy of the stored contents. If there is a mismatch between the checksums at the time of reading, it is determined that the memory is abnormal or the data could not be written normally at the time of writing, and the replacement part or main body mounting the memory is broken.

[0005]

However, in the method of diagnosing a failure by checking with a checksum, for example, even if there is no abnormality in data only in a part that is not so important, even if it is a completely new replacement part, even if it is a new replacement part, Is determined to be abnormal and becomes unusable.

[0006] This significantly reduces the convenience of the body and replacement parts.

In order to end writing stably,
For example, there are means such as maintaining the power supply during the writing period by using an auxiliary power supply even if the power supply is cut off. However, these methods are not suitable for a personal use printer because the cost is increased and the size of the apparatus is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an image forming apparatus capable of reliably backing up apparatus information in any situation. It is in.

[0009]

In order to achieve the above object, an image forming apparatus according to the present invention includes a non-volatile memory for storing changes over time of the apparatus, and interrupts data writing to the non-volatile memory. It is characterized by having control means for predicting and controlling data writing so that writing of a predetermined data amount is completed before interruption.

Here, it is preferable that the control means sets the data write start timing.

It is also preferable that the control means limits the amount of data to be written.

On the other hand, it is also preferable that the control means limits the amount of write data by selecting write data according to the importance of the information.

In the image forming apparatus according to the present invention, the image forming apparatus further includes a non-volatile memory for storing time-dependent changes of the apparatus, the non-volatile memory is divided into a plurality of areas, and different types of data are stored for each area. It is characterized by the following.

Here, it is also preferable to write data at a different timing for each area.

On the other hand, it is also preferable to treat the data differently for each area.

It is also preferable to set the data to be stored for each area according to the importance or urgency of the information indicated by the data.

Further, in the above-described image forming apparatus, it is preferable that a nonvolatile memory is mounted on the photosensitive drum.

A method according to the present invention is a method for controlling an image forming apparatus having a non-volatile memory for storing changes over time of the apparatus, wherein the method predicts interruption of data writing to the non-volatile memory and sets a predetermined data amount. And a control step of controlling data writing such that writing of data is completed before interruption.

Further, the nonvolatile memory is divided into a plurality of areas,
It is characterized by having a data write control step of storing different types of data for each area.

Further, a storage medium according to the present invention is a computer-readable memory storing a control program for an image forming apparatus having a non-volatile memory for storing a change over time of the apparatus, wherein interruption of writing data to the non-volatile memory is interrupted. It is characterized by storing a control program for predicting and controlling data writing so that writing of a predetermined data amount is completed before interruption.

Further, the nonvolatile memory is divided into a plurality of areas, and a data write control program for storing different types of data for each area is stored.

According to the present invention, by adopting the above configuration, the memory write timing is excluded from the timing at which the write is interrupted, and the amount of data to be written at once in an emergency is divided into smaller units. The unit of the divided data and its writing timing are switched according to the state of the image forming apparatus, the importance of the data, or the rotation.

As a result, a memory error due to an emergency interruption during data writing can be reduced without hindering downsizing and cost reduction, and even if a worst-case memory error occurs, the image forming apparatus can be as small as possible depending on the importance of data. Do not interrupt operation.

[0024]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, unless otherwise specified, the relative arrangement of components, program modules, and the like described in this embodiment, and numerical values such as resolutions are intended to limit the scope of the present invention to them only. Not something.

[First Embodiment] FIG. 1 is a conceptual block diagram of a nonvolatile memory and a power supply line of an image forming apparatus according to a first embodiment of the present invention. Hereinafter, the figures will be briefly described.

In FIG. 1, reference numeral 1 denotes an image forming apparatus including a replacement part 2. The image forming apparatus 1 is controlled by the CPU 3. Reference numeral 5 denotes a power supply line. The CPU 3 manages the power supply of the image forming apparatus, and controls the power supply disconnection circuit 6 through the control line 12. 7 is a power switch.

The image forming apparatus is provided with a fixing device 9 and a high-pressure unit 10 for operating such a device. In order to safely remove paper jams and the like, when the door is opened, these devices are opened. Is automatically connected to a power supply line. The door switch 8 is connected to the CPU 3 via a control line 13.
The CPU 3 can detect that the door is open.

Reference numeral 2 denotes a photosensitive drum unit, which comprises a photosensitive drum for forming an image and a waste toner box for storing waste toner after the image is formed, and is a replacement part that needs to be replaced after use for a predetermined life. The photosensitive drum unit 2 has a built-in EEPROM, and maintains information such as the total use time for calculating the life of the photosensitive drum by serial communication with the CPU 3 through the contact 17.

Next, control when the power switch is turned off will be described.

The power-off circuit 6 is a switch that can be controlled by the CPU 3. Power switch 7 and power disconnection circuit 6
Are connected by a control line 14. When the power supply switch 7 is turned on, the power supply disconnection circuit 6 is in a short-circuit state, of course. Even if the power supply switch 7 is subsequently turned off, the power supply disconnection circuit 6 maintains the short-circuited state until instructed by the control line 12 from the CPU 3. That is, the CPU 3 detects that the power switch 7 is turned off through the control line 11, performs a predetermined process described later, controls the power supply cutoff circuit 6 through the control line 12, and turns off the power of the image forming apparatus.

Next, control when the door is opened will be described.

The image forming apparatus is provided with a door for clearing a jam or replacing a consumable part. When the door is opened, a fixing unit or a high-voltage unit, which is dangerous if a user touches the door, is provided. Etc. are cut off by hardware for safety. CPU is not controlled by CPU
This is for safe operation even during runaway. The door switch 8 performs this function. The door switch 8 is installed in conjunction with the door of the image forming apparatus, and when the door is opened, the power supply to the fixing unit 9, the high-voltage unit 10, and the like is physically stopped.

At this time, the CPU 3 detects a door open through the control line 13 so as not to erroneously determine that these power supply cutoffs during operation are abnormal. The door open detection is a mechanism for detecting that power is no longer supplied to parts such as the fixing device 9 and the high-voltage unit 10. Therefore, if the power switch is on, the door is detected as open while the CPU 3 is operating even when the power supply to the entire image forming apparatus is stopped. The CPU 3 performs the same processing as the door opening as long as the CPU 3 operates.

Next, the process of writing to the EEPROM will be described.

When the power switch is turned off or the door is opened, the replacement part 2 may be replaced.
The contents of the ROM 4 must be updated to the latest information. Then, when the CPU 3 detects the power switch off from the control line 11 or the door open from the control line 13,
Write the latest information to EEPROM4.

However, when the power supply of the entire apparatus is cut off, the power supply to the EEPROM 4 is naturally cut off. In the middle of writing to EEPROM 4,
If the power supply to the power supply is cut off, the written data does not match the checksum and becomes abnormal. The same applies when the power supply to the CPU 3 is interrupted on the way.

The time from when the door is opened until the photosensitive drum as a replacement part is pulled out by the user is EE.
If it is earlier than the completion of the writing to the PROM 4, the writing is interrupted and the data becomes abnormal.

In order to avoid these abnormalities, writing to the EEPROM 4 is started and terminated at a predetermined timing. Then, in order to complete the writing to the EEPROM 4 during this predetermined period, the amount of data to be written is limited to a predetermined amount. This interval and data amount are determined as follows.
FIG. 3 illustrates the timing of detecting the drop of the power supply voltage and the door open when the power is turned off, and the timing of disabling the memory writing. The write start and end timings and the write data amount are determined based on the door open detection timing, the timing at which writing to the memory becomes impossible when power supply to the entire apparatus is stopped, and the user's exposure from the door open. Determined from the shortest time the drum can be pulled out.

In FIG. 3, reference numeral 37 is a graph showing a voltage drop when the power supply is completely cut off. From this graph, the door open detection voltage of 30, and the memory write disable voltage of 31, the door open detection timing 33,
The memory write disable timing 35 can be obtained. Here, the memory write disable voltage 31 is determined by the CPU and E
It shows the lowest voltage at which both of the EPROMs are completely inoperable.

Numeral 34 indicates the shortest time in which the photosensitive drum can be removed from the door open due to the configuration of the image forming apparatus.

38, 39, and 40 are different EEPs
It shows a ROM write start timing and a write completion time.

For example, 38 starts writing immediately after detecting the door open. However, at the time of the door open detection, the CPU 3 cannot distinguish whether the door is actually open or the power of the entire apparatus is cut off.
If the data write end timing is set after the memory write disable timing as described above, if the power is turned off, the data writing is stopped during the data writing.
, Writing to the memory becomes impossible. Therefore, the written data becomes abnormal.

Reference numeral 39 denotes a state in which the writing of data is waited until the writing impossible timing when the power is turned off, and after the writing impossible timing, it is determined that the door is normally open. Is to start. However, if data writing is set such that the data writing end timing is later than the shortest timing 36 at which the user can pull out the photosensitive drum, the data writing may be interrupted at this timing. There is.

Thus, it can be seen that the data may be written to the memory from either the door open detection 33 to the memory write disable timing 35 or from the memory disable timing to the interruption 36 by the user operation. Of these two periods, from the memory write disable timing 35 to the user's interruption timing 3
6 is longer, it is desirable to set the write start timing and the data amount so that data is written during this time, thereby preventing a data error from occurring at the time of emergency writing.

Next, control by the CPU 3 when the door is opened and the power switch is turned off will be described.

FIG. 4 is a flowchart showing the control flow of the CPU 3.

After the power is turned on in step S58, the image forming apparatus performs a predetermined initialization processing step S57, and upon completion of the initialization, proceeds to a normal processing step S56. The initialization processing step S57 is preparation necessary for performing a printing operation in an image forming apparatus such as an I / O or a drive system.
In this process, reading processing from the EEPROM is also performed. The normal processing step S56 is processing for repeating the printing operation. Steps S57 and S58 are generally performed by a known technique, and the details are omitted here.

When the door open is detected during the normal processing, the flow shifts to the flow starting from step S48. Then, the emergency stop processing of step S49 is performed first. The emergency stop processing step S49 stops all the drive systems that are not forcibly stopped by the power-off due to the door open, and also stops the task of controlling the parts forcibly stopped by the power-off. Then, in step S50, a time is waited until a timing at which writing is impossible. This timing is determined by a timer that starts counting from the time of door open detection. After the write disable timing, the process proceeds to step S51. In the case of the door open detection not by the door open but by the power-off, the writing process cannot be performed at all beyond the write disable timing, so that no data abnormality occurs due to the writing. In step S51, the checksum of the entire write data is calculated. Then, in step S52, EEPRO
Start writing to M. The process of writing to the EEPROM operates in parallel with the main process shown in FIG. In step S53, the process waits for the end of the process. Upon completion of the writing process, the flow shifts to step S54 to wait until the door is closed. If the door is closed while waiting in step S54, the process returns to the initialization process in step S57, and after the initialization process is completed, the process returns to the normal process.

When a jam occurs, the door is opened in accordance with the flow and jam paper processing is performed.

Next, the process of turning off the power supply will be described. The power switch on state including the door open process is step S55. If the power switch is off while the power switch is on, the process proceeds to step S40. The process when the power switch is turned off is almost the same as the process when the door is opened. However, when the power switch is turned off while the door is open, writing to the EEPROM may be in the middle of writing. After the stop processing, it is checked whether the data is being written to the EEPROM. If the writing is not being performed, the writing process is started in the same manner as when the door is opened. Step S4
In step S3, a checksum is calculated, and writing is started in step S44. After confirming the completion of writing in step S45, the power is turned off in step S46, and the process ends.

Note that the amount of write data is limited so that the time from the start of writing in steps S52 and S44 to the completion of writing is within a time that is not interrupted by the user's operation. Shall be

As described above, by setting the writing timing and the writing amount at the time of emergency writing in accordance with the detection timing of the writing timing of the image forming apparatus and the writing interruption timing, the writing interruption can be performed with a low cost and a simple configuration. Can eliminate data abnormalities.

In this embodiment, the door open detection and the write interruption timing are as shown in FIG. 3. However, the present invention is not limited to this. However, if the writing time is longer than the timing from the writing disable timing to the interruption timing by the user, the EEP starts immediately after the door open detection.
It is effective to limit the amount of data to be written so that writing to the ROM is started and completed by the timing at which the memory cannot be written. In addition, it is effective to set the timing and the data amount not only for the door opening but also for other emergency writing.

Next, a method for limiting the amount of write data will be described.

In this embodiment, the data amount is limited only at the time of emergency writing. Figure 5 shows the EEPR
It is a memory map of data written to OM. The total amount of data to be written is not limited, but instead is divided into three regions. The checksum is calculated and stored for each area.

In the area 1 (60), information whose quality is the highest priority is collected by limiting the amount of write data in an emergency. And checksum 1 calculated only in area 1
It has (61) in it. When the door is opened and the power switch is turned off, only the area 1 is written.

The area 2 (62) is a collection of data having a lower priority than the area 1. Then, it includes a checksum 2 (63) for area 2. The area 2 is updated at a predetermined interval in the normal processing. In the present embodiment, it is assumed that it is updated every time one printing operation is completed. Although the data is updated in the normal processing, the data is not updated when the door is opened or the power switch is turned off, so that the stored data may be out of date. The data which can accept it is handled in area 2.

The area 3 (64) is updated during the normal processing similarly to the area 2, but is not updated until the contents in the area 3 change significantly. Although the quality of the data is lower than that of the area 2, contents which can accept the data are handled in the area 3. Region 3 contains checksum 3 (65) of region 3.

As described above, the priority is determined based on the quality required for the data, and the area is divided and handled.
The data amount can be increased while eliminating data abnormalities due to interruption of writing with a low cost and simple configuration.

In the present embodiment, the area is set to 3
Although it is divided into two, it is not limited to this, and it is also effective to divide and manage into two or four or more. Further, in the present embodiment, the writing timing is controlled separately for emergency writing and normal processing. However, three or more writing timings in which the amount of data that can be safely written is divided into several stages. If there is, it is also effective to determine the priority for each timing and data amount.

In this embodiment, a photosensitive drum is used as an example of a replacement part, and an EEP is used as an example of a nonvolatile memory.
Although a ROM is mentioned, the present invention is not limited to this, and the present invention is effective even when another memory device is used for another replacement part.

[Second Embodiment] FIGS. 2 and 6 show a second embodiment of the present invention. In the above-described first embodiment, the replacement parts are provided with the EEPROM, but in the present embodiment, the apparatus body is provided with the EEPROM. Since the block configuration of the other image forming apparatus is the same as that of the first embodiment, the same components are denoted by the same reference numerals and description thereof will be omitted.

FIG. 2 is a conceptual block diagram of a nonvolatile memory and a power supply line around the image forming apparatus according to the present embodiment. The figure will be briefly described below.

The image forming apparatus according to the present embodiment has a nonvolatile memory (EEPROM) mounted on the main body of the image forming apparatus. Reference numeral 20 denotes an EEPROM for storing information of the main body. The EEPROM 20 and the CPU 3 perform serial communication via the control line 21 to back up data.

In this embodiment, since the nonvolatile memory is built in the main body, there is no need to write when the door is opened, unlike the first embodiment. Therefore, data writing is performed only when the power switch is turned off.

The flow of the processing in this embodiment is the same as that in FIG. 4 described in the first embodiment, except that it is not written every time the door is opened, so that the description is omitted.

FIG. 6 is a memory map of data to be written to the EEPROM in the image forming apparatus according to the present embodiment.
The total amount of data to be written is not limited, but instead is divided into five regions. The checksum is calculated and stored for each area.

Reference numeral 70 denotes a management area. 72, 74, 7
Reference numerals 6 and 78 are a region 1, a region 2, a region 3 and a region 4, respectively. Each area has a checksum 71, 73, 7
5,77,79. The areas 1, 2, 3, and 4 have no higher or lower priority. However, what is written by one emergency write is the management area and any one of the four areas, that is, two areas in total. Which of the four areas is to be written is determined by rotation. Area 1
Is written in the area 2 at the time of the next write after the write. Next to the area 2 is 3.3, the next to the 4.4 is 1 after the 4.4. Which area was written last time is stored in the management area.

By reducing the amount of data to be written at one time, data errors due to interruption during writing can be eliminated.

As described above, by dividing the write data into areas and backing up the data by rotation, the amount of data to be written at a time is reduced. Becomes possible. According to this means, it is possible to maintain the quality (newness) of all data on average.

In the present embodiment, the area is set to four.
However, if the amount of data that can be safely written is further increased, it is also effective to complete the writing in a shorter time by dividing the data into three or less and five or more. is there.

(Third Embodiment) FIG. 7 shows a third embodiment of the present invention.

Since the block configuration of the image forming apparatus according to the present embodiment is the same as that of the first embodiment,
Omitted.

In the present embodiment, unlike the image forming apparatus of the first embodiment, the data amount is not limited. FIG. 7 shows an EE of the image forming apparatus according to the present embodiment.
4 is a memory map of data to be written to a PROM. The total amount of data to be written is not limited, but instead is divided into three regions. The checksum is calculated and stored for each area.

Reference numeral 80 denotes a management area. This area manages how the entire data including the areas 1 and 2 is used. Here, the version number of the memory map in the development process is stored. 81 is an area 1 and checksum 1 (8
2). 83 is an area 2 and checksum 2 (8
4) is included. Next, the difference in how to handle each area will be described.

The area 1 stores information for improving the image quality. Here, the history of the use time of the drum, the application of a high voltage, and the like are stored and used as information for improving the image quality. If an abnormality occurs in this information, at the worst, the image quality only deteriorates. Therefore, forcing the replacement of the photosensitive drum only when a data error occurs here deteriorates usability. Therefore,
When a data error occurs in this area, only a warning of image quality deterioration is displayed, and the operation of the image forming apparatus is not stopped.

The area 2 holds information for avoiding a situation that leads to a physical failure of the image forming apparatus. For example, in the present embodiment, information on the amount of waste toner is held. Means for accurately ascertaining the fullness of the waste toner optically and based on the usage history thereafter will be omitted. If the photosensitive drum is forcibly rotated in a state where the waste toner is full, fatal damage is given to the image forming apparatus. Therefore, the status of the waste toner must be accurately grasped.
Therefore, a data error in the area 2 causes the operation of the image forming apparatus to stop in order to prompt the exchange of the photosensitive drum.

The management area is not updated in normal use. Further, although the information is related to the area 1 and the area 2, since the information is managed separately in the area 1 and the area 2, the data error in the management area cannot be distinguished between normal and abnormal. Therefore, errors in the management area are ignored.

As described above, the usability in the event of a data error in the memory can be improved by dividing the write data into regions according to the contents and distinguishing the measures taken by the image forming apparatus in the event of a data error. It became possible to improve.

In the present embodiment, the region is divided into three regions and treated differently. However, the region is not limited to three regions.
It is also effective to divide the area into two or four or more areas. Further, in the present embodiment, for example, the management area is set as an area in which the error check is ignored. However, it is also possible to display a warning so that the divided area is handled as an image forming area. Appropriate settings should be made in relation to the usage form and cost of the device. The scope of the present invention includes this.

[Other Embodiments] Even if the present invention is applied to a system composed of a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), an apparatus (one device) For example, the present invention may be applied to a copying machine, a facsimile machine, and the like.

An object of the present invention is to provide a storage medium storing a program code of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (or CPU) of the system or the apparatus.
And MPU) read and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

Examples of the storage medium for supplying the program code include a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, and CD.
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instructions of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the above-described flowcharts. A control program for predicting the interruption of writing and controlling the writing of data so that writing of a predetermined amount of data is completed before the interruption, or dividing the nonvolatile memory into a plurality of areas, and different types of data for each area Any of the program codes of the data write control program for storing the data may be stored in the storage medium.

[0088]

As described above, according to the present invention, the write timing and the write data amount at the time of emergency and normal operation are appropriately set, and the area is divided according to the contents of the data to be written. By appropriately setting which area and how much data is to be written at the appropriate timing, abnormalities in data stored in the non-volatile memory can be reduced, and in the worst case, if the data becomes abnormal, user convenience can be improved. An image forming apparatus that does not hinder the operation can be realized.

[0089]

[Brief description of the drawings]

FIG. 1 is a block diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a voltage drop and a write timing when power is turned off and a door is opened.

FIG. 4 is a flowchart illustrating a control flow of a CPU according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a memory map of a nonvolatile memory according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a memory map of a nonvolatile memory according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a memory map of a nonvolatile memory according to a third embodiment of the present invention.

Claims (13)

[Claims] An image forming apparatus including a nonvolatile memory for storing a change with time of the apparatus, wherein interruption of writing of data to the nonvolatile memory is predicted;
An image forming apparatus, comprising: control means for controlling data writing so that writing of a predetermined data amount is completed before interruption. 2. The image forming apparatus according to claim 1, wherein said control means sets data write start timing. 3. The image forming apparatus according to claim 1, wherein said control means limits an amount of data to be written. 4. The image forming apparatus according to claim 3, wherein said control means limits the amount of write data by selecting write data according to the importance of information. 5. An image forming apparatus comprising a non-volatile memory for storing changes over time of an apparatus, wherein the non-volatile memory is divided into a plurality of areas, and different types of data are stored for each of the areas. apparatus. 6. The image forming apparatus according to claim 5, wherein data is written at a different timing for each area. 7. The image forming apparatus according to claim 5, wherein different error checks are performed on data for each area. 8. The image forming apparatus according to claim 5, wherein data to be stored for each area is set according to importance or urgency of information indicated by the data. 9. The image forming apparatus according to claim 1, wherein said nonvolatile memory is mounted on a photosensitive drum unit.
An image forming apparatus according to any one of the preceding claims. 10. A method of controlling an image forming apparatus having a nonvolatile memory for storing a change with time of an apparatus, comprising: predicting interruption of data writing to the nonvolatile memory;
A method for controlling an image forming apparatus, comprising a control step of controlling data writing so that writing of a predetermined amount of data is completed before interruption. 11. A method for controlling an image forming apparatus having a non-volatile memory for storing changes over time of an apparatus, comprising: dividing the non-volatile memory into a plurality of areas; and storing data of different types for each area. A method for controlling an image forming apparatus, comprising a writing control step. 12. A computer readable memory storing a control program for an image forming apparatus having a non-volatile memory for storing changes over time of the apparatus, wherein the computer predicts interruption of data writing to the non-volatile memory,
A computer-readable memory storing a control program for controlling data writing such that writing of a predetermined amount of data is completed before interruption. 13. A computer-readable memory storing a control program for an image forming apparatus having a non-volatile memory for storing changes over time of the apparatus, wherein the non-volatile memory is divided into a plurality of areas, and different types are used for each of the areas. A computer-readable memory storing a data write control program for storing data.