JPH08297606A - Image formation device - Google Patents

Abstract

PURPOSE: To preserve a temporarily set optimum set value and to stably operate the device by providing an area for setting various conditions required for an SDRAM, and setting access from the outside to that area. CONSTITUTION: At the time of writing, an address position to first write data, the number of clocks from the supply of address to the setting of writing data, length at the time of continuous access and the order of address changes at the time of continuous access or the like are set to a setting means 2 as set values and after the set values of the setting means 2 are reset to the prescribed internal register of the SDRAM at an image storage means 1 by a setting control means 3, writing is started. At the time of reading, similarly, reading is performed according to the contents of the setting means 2 by the setting control means 3 and based on read image information, image formation is performed by an image forming means 6. Thus, the optimum set values are temporarily written in the setting means 2 so that the SDRAM can be read/ written according to those set values anytime.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of an SDRAM for storing image information in an image forming apparatus such as an electrophotographic copying machine, a printer and a fax machine.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus that stores image information, reads it out, and forms an image, an SRAM (Static Random Access Memory) needs a large capacity in order to process the image information at high speed. In that case, DRAM (Dynamic Random Access Memory) was generally used. But the micro CPU
Due to the demand for higher speed of printers and printers and improvement of image quality, a large capacity memory for image information has been required at a higher speed and at a lower cost in recent years. As a method of satisfying the demand, an SDRAM which operates in synchronization with a clock in recent years
(Synchronous dynamic random access
Memory) has come to the fore. This SDRAM
However, it is troublesome to set necessary conditions such as a time (clock number) until reading and writing of data, a length of continuous access, an address of continuous access, etc. each time of reading and writing. In particular, when the clock of the micro CPU and the clock of the SRAM are shared, when the operating frequency of the micro CPU is changed, the type of SDRAM is changed,
In some cases, it was necessary to change the control circuit of the SDRAM.

[0003]

As described above, the conventional S
In an image forming apparatus using a DRAM, it is troublesome to set required conditions such as a time (clock number) until data reading / writing, a length during continuous access, and an address during continuous access each time when reading / writing. In particular, when the clock of the micro CPU and the clock of the SRAM are shared, if the operating frequency of the micro CPU changes, the type of SDRAM or the control circuit of the SDRAM needs to be changed. Was occurring.

[0004]

SUMMARY OF THE INVENTION The present invention is a conventional SDRA as described above.
The present invention has been made in order to solve the problems of the image forming apparatus using M. By providing a dedicated area for setting various conditions required by the SDRAM, it is possible to easily access and set the area from the outside. In addition, the set value can be automatically changed according to the change of the operating frequency of the micro CPU, and moreover, the optimum set value can be set once without changing the type of SDRAM and the control circuit of SDRAM. An object of the present invention is to provide an image forming apparatus configured to store set values and operate stably.

[0005]

In order to achieve the above object, the first means of the present invention is to store S of image information as a first means.
In an image forming apparatus using a DRAM, an image storage means having an SDRAM for storing image information, a setting means for setting conditions required by the SDRAM at the time of reading / writing the image storage means, and at the time of reading / writing the image storage means And a setting control unit for controlling reading and writing according to the contents set in the setting unit.

A second means is characterized in that the image forming apparatus of the first means is provided with an external setting means for externally setting the set value of the setting means.

Further, the third means of the present invention is characterized in that, in the image forming apparatus of the first means, the setting means is a ROM placed in the image forming apparatus.

In the fourth means, the above first, second,
In the image forming apparatus of the third means, when the clock frequency supplied to the SDRAM of the image storage means is changed, the setting value of the setting means is set previously based on the ratio to the clock frequency before the change. It is characterized in that a setting value changing means for changing the setting value so as to correspond to the clock closest to the value is provided.

[0009]

As described above, the present invention provides, as the first means,
In an image forming apparatus using an SDRAM for storing image information, an image storage unit having an SDRAM for storing image information, a setting unit for setting conditions required by the SDRAM when reading and writing the image storage unit, and the image storage unit. Since the setting control means for controlling reading and writing according to the contents set in the setting means at the time of reading and writing of the means is provided, S
Once the optimum conditions for operating the DRAM are set by the setting means, the set values are saved for a long time,
Based on the set value, stable writing and reading to the SDRAM are possible.

In the second means, the image forming apparatus of the first means is provided with the external setting means for externally setting the set value of the setting means, so that the operating frequency of the micro CPU is changed. Also SDRAM type and SDRA
It is not necessary to change the control circuit of M, and the set value can be easily changed from the outside.

Further, in the third means of the present invention, in the image forming apparatus of the first means, since the setting means is a ROM placed in the image forming apparatus, the micro CPU
It is possible to share the ROM in which the above program is stored.

In the fourth means, the above first, second,
Alternatively, in the image forming apparatus of the third means, when the clock frequency supplied to the SDRAM of the image storage means is changed, the setting value of the setting means is changed to the previous value based on the ratio with the clock frequency before the change. Since the setting value changing means for changing the setting value so as to correspond to the clock closest to the setting value is provided, even if the clock frequency of the SDRAM is changed, the optimum setting conditions are automatically calculated and stored. .

[0013]

The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing a main configuration of a printer showing an embodiment of the present invention. Although a printer is illustrated as an image forming apparatus in this example, the present invention can be widely applied to other image forming apparatuses. The printer shown in this example includes an image storage unit 1, a setting unit 2 for setting conditions necessary for the operation of the image storage unit, a setting control unit 3 for controlling the setting unit, an image forming apparatus 6, and a storage unit. The device ROM / RAM 7 and the external connection means 8 are connected via the overall control means 9. An external device 20 has a function of supplying image data to the image forming apparatus.

The operation and function of each section in this configuration will be described.

In the configuration shown in FIG. 1, it is assumed that image information is supplied from an external device 20 such as a computer via the external connection means 8 of the image forming apparatus 10. In order to support a computer capable of high-speed processing in recent years, the image storage means in the image forming apparatus is a high-speed and large-capacity memory as described above, and an SDRAM that operates at the same time in synchronization with a high-speed clock signal. (Synchronous Dynamic Random Access Memory) is used. This SDRAM is burst
If the address of the first reading position is given during reading (continuous reading), the set time (CAS L
After that, the first data is output, and from that time, the data read in the address order by the length set for each clock (the length set as Burst Length) is output. Is output. Similarly, at the time of burst write (continuous write), if the address of the first write position is given and the write data is given for each clock, the continuous write is performed in the address order by the length designated by the setting. Is done. Unlike conventional DRAM (Dynamic Random Access Memory), it is not necessary to always give an address to each data to read and write,
High-speed data read / write is possible.

Further, in order to store or read the image information received through the external connection means 8 at high speed in the SDRAM of the image storage means 1, various set values are given in addition to the first read / write address. There is a need. In the present invention, the setting means 2 is provided in order to prepare the set value in advance. In this embodiment, reading and writing to the image storage means 1 are controlled according to the contents set in the setting means 2 by the setting control means 3. This will be explained concretely. At the time of writing, the address position to be written first, the number of clocks until the write data is set after supplying the address, the length at the time of continuous access, and the change of the address at the time of continuous access Order etc.
It is set in the setting means 2 as a set value, and the setting value of the setting means 2 is set by the setting control means 3 in the SDRA of the image storage means 1.
After resetting to a predetermined internal register of M, writing is started. Similarly, at the time of reading, the setting control unit 3 reads the image according to the contents of the setting unit 2, and the image forming unit 6 forms an image based on the read image information. The control unit 9 generally includes a micro CPU, transmits information between each unit of the image forming apparatus 10 and gives an operation instruction according to timing, or monitors whether or not each unit is operating normally. It has a function to do.
A program for controlling the micro CPU is stored in the ROM of the ROM / RAM 7, and the RAM is used as a memory for temporarily storing various calculation results.

According to this structure, once the optimum set value for operating the SDRAM can be written in the setting means, the SDRAM can be read and written according to the set value at any time, and the frequency of the clock supplied to the SDRAM can be changed. Even so, it is only necessary to change the set value by the setting means.

FIG. 2 is a block diagram showing a modified embodiment of the present invention. In addition to the functions described in FIG. 1, an external setting means 4 and a set value changing means 5 are added. . Overlapping description will be omitted, and only functional operations different from those in FIG. 1 will be described. That is, as the setting means 2 for setting the set value of the SDRAM, for example, a dip switch, RA
M or ROM may be considered, but the external setting means 4 is for allowing the setting value contents of the setting means 2 to be externally set and changed, and for example, an operation panel (not shown) of the image forming apparatus 10 is provided. When the set value is input from the key of, the external setting means 4 judges the contents, and the RAM of the setting means 2
It becomes possible to write in. Furthermore, when the set value data is received from the external device 20 via the external connecting means 8, the set value content can be judged by the external setting means 4 and similarly written in the RAM of the setting means 2. Of course, it is also possible to operate the dip switch to determine the set value.

As described above, according to this embodiment, the setting value of the setting means 2 can be set from the outside, so that the type of SDRAM can be changed even if the operating frequency of the micro CPU changes, as will be described later. The optimum setting value of the SDRAM can be easily reset from the external setting means without changing the control circuit of the SDRAM or SDRAM.

Also, in the above embodiment, the setting means 2 is used.
May be set as a ROM and a part thereof may be set as a dedicated area for storing the set value, but from the viewpoint of cost merit, the ROM / RAM used for the program of the micro CPU
If the method of diverting 10 ROM partial areas is used, it is not necessary to provide a dedicated ROM, which is advantageous in cost reduction.
In this case, the setting control means 3 causes the ROM / RAM
SDRA set in a predetermined area of 10 ROMs
The set value of M is detected, and the reading / writing of the image storage means 1 is controlled according to the set content.

One of the great advantages of SDRAM is that it operates in synchronization with a clock signal.
Generally, the clock of the SDRAM and the clock of the micro CPU are commonly used, and therefore, for example, the micro CP
When the clock frequency is increased in order to increase the operating speed of U, the operating speed of the SDRAM is naturally increased, and a malfunction may occur at the set value corresponding to the low frequency set in the setting means 2. For example, the number of clocks is set so as to secure a time for performing other processing while reading and writing data after supplying an address to the SDRAM, but when the frequency of the clock is changed, the secured time is set. It makes a difference. For this reason, other necessary processing cannot be performed, and a malfunction may occur. The set value changing means 5 is installed to prevent the malfunction, and even if the clock frequency supplied to the SDRAM is changed, the address is set in the SDRAM in consideration of the change ratio before and after the change of the clock frequency. The number of clocks is set so that the time for performing other processing is secured while reading and writing the data after the supply. That is, for example, when the clock frequency is doubled, the number of clocks to be set is doubled. However, when the time required for other processing is shortened as the clock frequency is increased, that is Reduce the number of clocks. In this way, when the clock frequency is changed, the setting value is changed so as to correspond to the clock of the time closest to the setting time, so that the time for other processing can be secured as usual. As one of the methods for achieving this function, although not shown, the setting value changing means 5 is provided with a reference clock generating means having a frequency sufficiently higher than the clock supplied to the SDRAM.
It is checked and stored how many times one cycle of the DRAM clock corresponds to the reference clock (for example, this value is B). When the clock frequency is changed, it is similarly detected how many one cycle of the SDRAM clock after the change corresponds to the reference clock (for example, this value is A), and the ratio with the clock frequency before the change is detected. (A / B)
Is calculated. When the previous setting value of the setting means 2 is n, the new setting value is the closest integer m equal to or greater than the value calculated by n × (A / B), and the setting value changing means 5 sets the setting value 2
The set value n of is changed to the set value m. According to this method
Even if the operating frequency of the clock supplied to the SDRAM changes, the set value can be automatically changed so as to secure the previously set time. That is, the second clock signal having a frequency sufficiently higher than the clock frequency counts the clock frequencies before and after the change, and based on the result,
The number of clocks for securing the time required for other processing may be calculated.

FIG. 3 shows the main timing of the SDRAM. In the example shown in FIG. 3, the CS (chip select) signal of the SDRAM to be selected is active (Low level) at the timing of setting the mode register in the SDRAM, and the column (row) address is set. The strobe RAS signal is active, and at the same time, the row (column) address strobe C
When the AS signal is active and the WE signal that is writable (write enable) is active, the value to be set (valid part in the figure) is set to the RA signal that is normally composed of multiple lines used as address input terminals. Just enter it.

FIG. 4 shows an example of the main timing of another SDRAM, in which the address of the first read position is given to the SDRAM (the RA and Row columns of the RA signal in the figure).
Is a diagram showing the timing at which the first data is output after the time set as CAS Latency). In this example, a column (row) address is given on the RA signal when the RAS signal is active, and a row (column) address is given on the RA signal when the CAS signal is active. Since the WE signal is at high level, it is in the reading state,
When the column (row) and row (column) addresses are adjusted at the rising edge of the eighth clock signal (SYSCLK signal in the figure), CAS Latency = 2 is set, so that the tenth clock signal The first data is established at the rising edge (D0 in the figure). After that, D1 for each clock,
Data is output as D2, .... Therefore, when the frequency of the clock (SYSCLK signal) supplied to the SDRAM is changed, the time t1 of CAS Latency changes with the setting of CAS Latency = 2. If the changed clock frequency is high, CAS Laten
The cy time is shorter than t1, and the CAS Latency time is longer than t1 when the changed clock frequency is low. If it is necessary to perform other processing during the time t1 before the change, if the clock frequency after the change becomes higher, it may not be possible to perform the other processing within the new CASLency time. If the clock frequency after the change becomes low, there is a margin in time after performing other processing, and the processing time becomes long, which causes a problem.
The set value changing means 5 of FIG. 2 is provided to eliminate the above-mentioned problems, and is configured to automatically set the minimum necessary time by the above-mentioned method.

[0024]

As described above, according to the present invention, the first means is provided with the setting control means for controlling reading and writing according to the contents of the setting means. Therefore, the optimum setting value for operating the SDRAM is set. Once the data can be written to the SDRAM, the SDRAM can be read and written according to the set value, and even if the frequency of the clock supplied to the SDRAM is changed, stable image formation can be performed only by changing the set value of the setting means. An image forming apparatus can be provided.

Further, in the second means of the present invention, since the setting value of the setting means can be set by the external setting means,
Even when the operating frequency of the micro CPU is changed, the optimum setting value of the SDRAM can be easily reset without changing the type of SDRAM or the control circuit of the SDRAM.

Further, according to the third means of the present invention, since the setting is done in the ROM area provided in the image forming apparatus, the SDRAM is shared in the ROM containing the program of the micro CPU. The setting value of the SDRAM can be entered, and the setting value of the SDRAM can be easily set without increasing the cost without providing special switches.

Further, according to the fourth means of the present invention, in the image forming apparatus of the above-mentioned 1, 2, or 3, S
Even when the clock frequency supplied to the DRAM is changed, the setting value is automatically changed to match the optimum timing condition once set. Therefore, when changing the operating frequency of the micro CPU, It is possible to provide an image forming apparatus that does not need to be changed or the control circuit of the SDRAM is changed, and that automatically maintains an optimum set value once set and stably processes image information.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an image forming apparatus showing an embodiment of the present invention.

FIG. 2 is a block diagram of a main part of another image forming apparatus showing an embodiment of the present invention.

FIG. 3 is a timing diagram showing a main operation of the SDRAM used in the embodiment of the present invention.

FIG. 4 is another timing chart showing the main operation of the SDRAM used in the embodiment of the present invention.

[Explanation of symbols]

1 ... Image storage means, 2 ... Setting means, 3 ... Setting control means, 4 ... External setting means, 5 ... Set value changing means, 6 ... Image forming means, 7 ... ..ROM / RA
M, 8 ... External connection means, 9 ... Control means, 10 ...
..Image forming device, 20 ... External device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoki Ishii 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (4)

[Claims] 1. An image forming apparatus using an SDRAM for storing image information, comprising: an image storage unit having an SDRAM for storing image information; and a setting unit for setting conditions required by the SDRAM when reading and writing the image storage unit. When,
An image forming apparatus comprising: a setting control unit that controls reading and writing according to the contents set in the setting unit when reading and writing the image storage unit. 2. The image forming apparatus according to claim 1,
An image forming apparatus comprising external setting means for setting the set value of the setting means from the outside. 3. The image forming apparatus according to claim 1,
An image forming apparatus, wherein the setting means is a ROM placed in the image forming apparatus. 4. The claim 1, claim 2, or claim 3.
In the image forming apparatus described above, SD of the image storage means
When the clock frequency supplied to the RAM is changed, the set value of the setting means is changed based on the ratio with the clock frequency before the change so that the clock corresponds to the clock closest to the previous set value. An image forming apparatus comprising a set value changing unit.