JP2016093925A - Printer and printing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printer which can reduce the number of access and access time to a main memory regardless of the position and inclination of a recording head when performing image formation with free hand scanning.SOLUTION: A printer 10 for performing printing with movement on a print medium comprises at least: a recording head 19 which can simultaneously record a plurality of pixels; positional information calculation means which obtains the current position and inclination of the recording head; a memory 12 which stores image data; and a control part 13 which has image reading means for reading the necessary pixel data from the memory and outputting it to the recording head on the basis of the positional information of the recording head. The image data stored in the memory 12 is divided into blocks at least including a plurality of pixels in the vertical and horizontal directions. The image reading means includes a sub memory which temporarily accumulates the image data and sub memory management means which associates the positional information of the recording head with the image data in the block unit to manage access to the memory.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printing apparatus and a printing system.

  In recent years, due to the downsizing of notebook PCs and the rapid spread of smart devices, printers are required to be downsized and portable. In response to such a request, a hand-held printing apparatus is known that forms an image while omitting a paper conveyance system as a printing medium and moving the paper on the paper by a user (operator).

As a combination of the position detection of the recording head and the moving direction (scanning direction) of the apparatus in the handheld printing apparatus, for example, a position detection function in one direction (for example, the X-axis direction) is provided, and printing is performed by scanning only in one direction. There are known ones that perform position detection in two directions (for example, X-axis and Y-axis directions) and perform printing by scanning only in two directions.
Furthermore, a printing apparatus that has a position detection function in three directions (for example, the X-axis, Y-axis, and rotation axis directions) and performs printing by freely moving (freehand scanning) on a plane has been proposed (for example, , See Patent Document 1).

  In Patent Document 1, in order to perform printing by freely moving a printing apparatus on a sheet plane, the position of a recording head arbitrarily moved by an operator is detected, and image data is read from a memory according to the position. A method of reading and printing is disclosed.

  However, since the movement of the recording head by the operator cannot be controlled, it is necessary to read the image data corresponding to the detected position of the recording head from the memory after detecting the position of the recording head. Since the recording head moves sequentially, if the time from detection of the position to reading of the corresponding memory becomes long, there is a problem that the error of the printing position becomes large due to the movement of the recording head during that time.

  Also, by scanning the recording head freehand, the recording head passes through the same region a plurality of times, resulting in ink overstrikes, resulting in wasted ink and uneven density in the formed image. May be.

  In order to prevent overprinting of ink, for example, it is necessary to rewrite image data of an already printed area into white data and return it to the memory. Including access to the memory for such writing back increases the number of accesses, and further increases the time for reading image data from the memory.

  SUMMARY An advantage of some aspects of the invention is that it provides a printing apparatus capable of reducing the number of accesses and the access time to a main memory regardless of the position and inclination of a recording head when an image is formed by freehand scanning.

  In order to achieve such an object, a printing apparatus according to the present invention is a printing apparatus that performs printing by moving on a print medium, a recording head capable of simultaneously recording a plurality of pixels, and a current position of the recording head Position information calculating means for obtaining the inclination, a memory for storing image data of an image to be printed by the recording head, and the necessary information from the memory based on the position information of the recording head calculated by the position information calculating means. A control unit having an image reading unit that reads out pixel data and outputs the pixel data to the recording head, and the image data stored in the memory is a rectangle or a substantially square including a plurality of pixels in at least the vertical and horizontal directions The image reading means is a sub-memory that temporarily stores image data in units of blocks, and A sub-memory management unit that associates recording head position information with block-unit image data and manages access to the memory for reading or writing necessary image data. is there.

  According to the present invention, when image formation is performed by freehand scanning, it is possible to provide a printing apparatus capable of reducing the number of accesses to the main memory and the access time regardless of the position and inclination of the recording head.

FIG. 2 is a block diagram illustrating an example of a hardware basic configuration of a printing apparatus according to an embodiment. It is a schematic diagram which shows an example of the electronic device and printing apparatus which comprise the printing system of this embodiment. 3 is a block diagram illustrating an example of a configuration of a control unit of the printing apparatus according to the present exemplary embodiment. FIG. 4A and 4B are schematic views showing the order in which image data is arranged on the memory. FIG. 4C is a memory arranged in units of lines, and FIG. It is a schematic diagram which shows the memory arrange | positioned by the square block unit. FIG. 6 is a schematic diagram for explaining a memory access amount required by a movement of a recording head. FIG. 3 is a block diagram illustrating an example of a configuration of an image reading unit (rotator) of the printing apparatus according to the embodiment. 6 is a flowchart illustrating a processing flow when a write request is generated from an address generation unit of the printing apparatus according to the embodiment. It is a schematic diagram explaining the difference in the memory transfer rate by block arrangement. 4 is a table showing information managed by a table management unit and a data storage unit of the printing apparatus according to the embodiment.

  Hereinafter, a printing apparatus and a printing system according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.

  FIG. 2 is a schematic diagram illustrating an example of a printing system according to the present embodiment. FIG. 2A is an electronic device that transmits image data to the printing apparatus according to the present embodiment, and FIG. 2 shows an example of printing by a handheld printer as a printing apparatus.

  As shown in FIG. 2B, the printing apparatus (handheld printer) 10 has a size and weight that can be operated by the user 80 with one hand, and can freely be flat on a printing medium 70 such as a notebook or printing paper. Scan (freehand) to form an image.

  Hereinafter, as an example of the printing apparatus 10, an inkjet printer including an inkjet recording head having a plurality of nozzles will be described. However, the printing apparatus 10 according to the present embodiment includes a recording head capable of outputting a plurality of pixels at the same time. If it is, it will not specifically limit, For example, a thermal head printer may be sufficient. Further, the printing apparatus 10 may be a monochrome printer or a color printer.

  The printing apparatus 10 receives image data from the image data output device 60 shown in FIG. 2A by wireless communication (schematically indicated by reference numeral 61), and forms an image on the print medium 70. The image data is not particularly limited, and examples thereof include text data composed of characters, document data including figures, pictures, photographs, and table data.

  The printing apparatus 10 can receive print setting information (for example, monochrome / color designation) together with image data from the image data output device 60, and can form an image based on the setting information.

  Examples of the image data output device 60 include electronic devices such as smartphones, tablet terminals, and notebook PCs. The image data output device 60 performs wireless communication (schematically indicated by reference numeral 61) with the printing apparatus 10 and transmits image data. The image data transmitted to the printing apparatus 10 may be data acquired from another device such as a server in addition to the data held by the image data output device 60.

FIG. 1 shows an example of a basic hardware configuration of the printing apparatus 10.
Firmware that performs hardware control of the printing apparatus 10 and drive waveform data of the recording head are stored in the memory 12.

  When image data (print job) is received from the image data output device 60 by the image data communication interface (I / F) 15, the control unit (control module) 13 is based on the input information from the navigation sensor 17 and the recording head 19. The position of each nozzle is calculated.

While moving on the print medium 70 by freehand scanning by the user 80, the printing apparatus 10 continues to calculate each nozzle position of the recording head 19, and an image corresponding to the calculated nozzle position (an image of the peripheral region is displayed). Data) is transferred from the memory 12. When it is determined that the transferred image matches the nozzle position, the image data is transferred to the recording head drive circuit 14.
The recording head 19 receives print timing information as well as image data from the recording head drive circuit 14 and discharges ink from each nozzle to the print medium 70 based on the timing.

  The operation unit 18 includes an operation button, a touch panel, a liquid crystal display (LCD), and the like. The operation unit 18 can receive input from the user and can notify the user of a processing status, an error, and the like.

  The printing apparatus 10 further includes a power supply 26 and a power supply circuit 11 that controls the power supplied to each unit.

FIG. 3 shows an example of the configuration of the control unit 13 shown in FIG.
The control unit 13 can be configured by, for example, an SoC (System on chip), an ASIC (Application Specific Integrated Circuit), and an FPGA (Field Programmable Gate alley).

  The SoC denoted by reference numeral 20 includes a CPU 21 that controls the entire printing apparatus 10, a memory controller 23 that controls the memory 12, and a position calculation circuit 22 that calculates the position of the recording head (each nozzle). These are connected to the bus 24 and exchange data and the like via the bus 24.

  The ASIC / FPGA denoted by reference numeral 30 includes a navigation sensor I / F 33, a timing generation unit 34, an image reading unit (rotator) 32 serving as an image reading unit, an interrupt notification unit 31, and a recording head control unit 35. Have. These are connected to the bus 36 and exchange data and the like via the bus 36.

  The bus 24 and the bus 36 are connected, and the SoC and the ASIC / FPGA exchange data and the like via the bus 24 and the bus 36.

  The navigation sensor interface (I / F) 33 communicates with the navigation sensor 17, receives an output value from the navigation sensor 17, and stores the value in an internal register which is an internal memory.

  The interrupt notification unit 31 notifies the SoC 20 when the navigation sensor I / F 33 ends communication with the navigation sensor 17 and notifies status information such as an error.

  For example, the timing generation unit 34 generates information on the timing at which the sensor emits light and acquires reflected light from the print medium 70 as image data, and sends the information to the navigation sensor I / F 34. As described above, the timing generation unit 34 instructs the navigation sensor 17 to read the print medium 70.

On the other hand, the CPU 21 reads the output value of the navigation sensor 17 and calculates the position of the recording head 19.
The position information of the recording head 19 calculated by the CPU 21 is input to the image reading unit (rotator) 32.

  The image reading unit (rotator) 32 calculates each nozzle position from the position information of the recording head 19 and reads image data corresponding to the nozzle position from the memory. Further, the image reading unit (rotator) 32 rotates the read image data in accordance with the position and inclination of the head, and outputs the image data to the recording head control unit 35 in the arrangement order required by the recording head 19.

  The timing generation unit 34 further generates timing information for driving the recording head 19, and sends the generated information to the recording head control unit 35. That is, the timing generation unit 34 instructs the timing for ejecting ink from the plurality of nozzles of the recording head 19 in order to perform printing.

  The recording head control unit 35 generates a control signal from the timing information for driving the recording head 19, receives the image data output from the image reading unit (rotator) 32, and determines from which nozzle the ink is ejected. To do. The recording head control unit 35 outputs information about nozzles for ejecting ink and image data to the recording head drive circuit 14 according to the determination result and timing information.

The image reading unit (rotator) 32 includes means for writing back information for preventing overstrike to the memory 12 (memory controller 23) in accordance with transmission of image data to the recording head control unit 35.
The information for preventing overstrike is not particularly limited as long as it is information indicating that an image in a predetermined area has been recorded. Examples of means for writing back to the memory 12 in units of pixels are as follows. .
(1) Means for clearing memory of recorded image data (2) Means for recording information indicating recorded separately from image data

The means (1) rewrites the original image data as non-ejection data (clears the memory).
The means (2) records information indicating that the image data is data corresponding to the recorded area, separately from the original image data.

In the case of the pattern (1), the memory access load is reduced because only the original image needs to be read. In addition, since only the reading and writing of the corresponding image data are required, an increase in the number of memory accesses can be suppressed.
On the other hand, in the case of the above pattern (2), it is necessary to read both the original image and the data indicating that it has been recorded, so the memory load increases. However, since the memory data of the original image is not destroyed, it is possible to realize a desired process (for example, a process of determining a character area and a graphic area and performing some process) according to the original image. In addition, when printing a plurality of pages, the original image data can be reused.

As described above, the printing apparatus according to the present embodiment is a printing apparatus 10 that performs printing by moving on the print medium 70, and includes the recording head 19 that can record a plurality of pixels simultaneously, and the current state of the recording head 19. CPU 21 as position information calculation means for obtaining position and inclination, memory 12 for storing image data of an image to be printed by the recording head 19, and position information of the recording head 19 calculated by CPU 21 as position information calculation means. And at least a control unit 13 having image reading means for reading out necessary pixel data from the memory 12 and outputting it to the recording head 19.
The image data stored in the memory 12 is divided into rectangular or substantially square blocks including a plurality of pixels in at least the vertical and horizontal directions.

The arrangement of the divided image data will be described with reference to FIG.
4A and 4B are schematic diagrams showing the order in which image data is arranged on the memory, and the arrows indicate in what order the image data is arranged in the memory. is there.
4C is a schematic diagram showing a memory in which image data is arranged in units of lines, and FIG. 4D is a schematic diagram showing a memory in which image data is arranged in units of substantially square blocks.
4A and 4C are aspects of the conventional printing apparatus, and FIGS. 4B and 4D are aspects of the printing apparatus 10 of the present embodiment.

In FIG. 4C showing a conventional example, image data for one line is arranged at continuous addresses on the memory (L1), and then image data for the second and subsequent lines is arranged on the memory (L2... Ln).
Since the printing apparatus 10 of the present embodiment performs image formation by scanning freehand, for example, when the recording head is arranged vertically in the drawing, dots (pixels) D arranged for each line L in each nozzle. Must be obtained from memory each time.
In the arrangement of image data shown in FIG. 4C, in order to acquire pixel data, jumping access is performed at each timing, memory access corresponding to the number of nozzles occurs, and efficiency decreases.

  On the other hand, in the printing apparatus 10 of this embodiment, as shown in FIG. 4D, by arranging the memory in block units B of approximately square blocks of M in the vertical direction and N in the horizontal direction, Efficiency is improved. That is, by arranging image data in a block B including a plurality of dots D in the vertical and horizontal directions, adjacent image data in the vertical and horizontal directions can be read out with a single memory access.

  If the shape of the block B is a horizontally long shape close to the line L, the number of accesses increases when the recording head is arranged vertically as in the conventional example, the efficiency decreases, and the shape of the block B is vertically long. With this shape, the number of accesses increases when the head is arranged horizontally, and the efficiency decreases.

The image data stored in the memory 12 is preferably divided into blocks in which the number of pixels in the vertical direction and the number of pixels in the horizontal direction are the same. Specifically, it is preferable that the divided blocks have a height of 8 to 32 dots and a width of 8 to 32 dots.
For example, the shape of the block B is preferably a shape close to a square as shown in FIG. 4D, and can be, for example, 16 dots × 16 dots.

  In addition, it is preferable to align the size of each block and the head address so that one block of image data can be read out by one memory access and the memory access efficiency can be improved. Specifically, the block size can be 64 bytes (16 dots × 16 lines × 2 bits / dot), and the head address of each block can be a multiple of 64.

  As described above, in the printing apparatus 10 according to the present embodiment, image data is stored in units of blocks, and data is arranged with a size and address (alignment) that can be accessed by one unit of memory read / write for one block. .

Next, the memory access amount required by the movement of the recording head will be described with reference to FIG.
FIG. 5A shows the position H1 of the recording head at the N-th ejection (N is an integer of 0 or more) and the block B1 that needs to be read. That is, when the recording head is at the position H1, the block B1 is an access target.
FIG. 5B shows the position of the recording head at the time of the (N + 1) th ejection, the position H2 of the recording head, and the blocks B1 and B2 that need to be read. Since the block that needs to be newly read out by the movement of the recording head is only the block B2 that is color-coded, the B1 data that has already been read out during the Nth ejection is held in the image reading unit (rotating unit) 32. If this can be done, the number of accesses to the memory can be reduced compared to the case where all blocks are read from the memory.

  The capacity required for the internal memory is the maximum number of blocks to be accessed at the time of one ejection (Nth ejection), the maximum number of blocks to be accessed at the next ejection (N + 1th ejection), and Is given as the sum of

In the example shown in FIG. 5B, since the areas indicated by B1a and B1b are not used in the (N + 1) th ejection, they can be released by discarding these data or writing them back to the memory.
For example, when masking the printed data and writing it back to the main memory, the data is written on the sub memory, and when the corresponding block is not used, it is written back to the main memory as a block. Therefore, the occurrence of overstrike can be prevented.

  By dividing the image data into small-sized blocks and rearranging the image data in advance so that the image data of the same block is continuously arranged in the memory, the main memory can be used regardless of the position and inclination of the recording head. It is possible to reduce the number of accesses to and the access size time.

  Also, the image data read from the main memory immediately before is stored in a sub-memory (image reading unit 32) that can be accessed at high speed. The number of accesses to the main memory can be further reduced by fetching only the blocks to be fetched from the main memory into the sub memory and reading out the data from the already stored sub memory with respect to the blocks that are not updated.

Details of the image reading unit (rotator) 32 for realizing the operation shown in FIG. 5 will be described with reference to FIG.
An image reading unit (rotator) 32 serving as an image reading unit includes a CPU interface (I / F) 41, a nozzle position generation unit 42, an address generation unit 43, an output interface (I / F) 44, a table management unit 45, and Each block of the data storage unit 46 is configured.

The data storage unit 46 is a sub memory that temporarily stores image data in units of blocks.
The table management unit 45 is sub memory management means for managing the access to the memory for reading or writing necessary image data by associating the position information of the recording head 19 with the image data in block units.

The CPU I / F 41 receives various setting information such as an image width, height, and resolution from the CPU 21. Further, for each ejection timing from the recording head, the position information of the recording head at that time is received.
In order to reduce the load on the CPU 21, it is preferable that the print head position information given from the CPU 21 is the minimum necessary data (for example, coordinates of both ends of the print head).

The nozzle position generation unit 42 generates position information for each nozzle each time it receives position information of the recording head once, and outputs the generated position information to the address generation unit 43.
The address generation unit 43 generates a memory address in which the data is stored based on the position information obtained from the nozzle position generation unit 42.

  The output I / F 44 converts the image data read from the memory into a format requested by the recording head control unit 35. Data is buffered as necessary.

The table management unit 45 associates the address generated by the address generation unit 43 with the data stored in the data storage unit 46.
The data storage unit 46 stores data read from the memory 12. Further, data to be written to the memory 12 is temporarily accumulated.

The table management unit 45 and the data storage unit 46 manage each piece of information shown in the table of FIG.
The table shown in FIG. 9 shows an example in which there are 32 blocks.
Each item is as follows.
enable: Valid / invalid of the corresponding block
TTL: Life of the corresponding block
dirty: A flag indicating that the value is different between the memory and the data storage unit. Stands when a light occurs in the corresponding block.
Addr: Indicates an address on a memory where data corresponding to the data of the corresponding block is stored.
Data: Copy and hold data in memory.

  The table management unit 45, which is a sub-memory management means, adds TTL (Time To Live), which is information indicating the lifetime for each block unit of image data, sets TTL by read and write access, and has a predetermined timing. Every time the TTL is counted down, data is discarded or written back to the memory from the block where the TTL has reached a certain value. Thereby, a block that has not been accessed for a long time can be released at an earlier timing.

The TTL set for each block of image data and managed by the sub memory management means is a value (V2) that is a threshold value (V1) that is written back to the memory 12 from the data storage unit 46 that is a sub memory. ) Is set to be above.
That is, it is set so as to satisfy V1 ≧ V2.
Even in a situation where reading has occurred, if the writing has not occurred for a certain period of time, it is possible to perform flashing. For example, even when the recording head 19 is stationary, the value of the memory 12 is the latest. Kept.

In addition, the TTL managed by the sub-memory management unit exceeds the value (V3) set at the time of writing exceeding the threshold (V1) to be written back to the memory 12 from the data storage unit 46 as the sub-memory. Is set as follows.
That is, it is set so as to satisfy V3> V1 + 1.
By realizing a cycle in which writing has occurred, a cycle in which writing has not occurred throughout the entire cycle, and a flow of flash, it is possible to avoid waste such as re-flushing after re-writing.

Further, the TTL managed by the sub-memory management unit is set so that the value (V2) set at the time of reading exceeds the value obtained by adding 1 to the threshold value (V4) used for the block discard determination.
That is, it is set to satisfy V2> V4 + 1.
A cycle in which reading has occurred, a cycle in which reading has not occurred throughout the entire cycle, and a flow of block release can be realized. Can be avoided.

  The operations of the table management unit 45 and the data storage unit 46 will be described with reference to the flowchart of FIG.

FIG. 7A shows the flow of processing (read operation) when a read request (read request) from the address generation unit 43 is generated.
After a read request is generated (S10), it is first determined in a read operation whether a cache hit or a miss hit (S11).
“Cache hit” indicates that the data of the address to be read is stored in the data storage unit 46. Specifically, enable == 1 and the address of the read request (the upper bit) is in the table. A cache hit is determined when there is a block that matches Addr.

  On the other hand, in the case of “miss hit” in which no cache hit occurs, first, the corresponding data is stored from the memory 12 into the data storage unit 46. In addition, the enable of the corresponding block is set to 1, and the address of the read request is set and updated in Addr, which is used for subsequent cache hit determination (S12).

Next, data is returned from the data storage unit 46 to the address generation unit 43 (S13).
If the TTL of the block is TTL <2, TTL = 2 is set (S14). In step S14, the TTL at the time of occurrence of reading is set to 2, which indicates that after the occurrence of reading, if the block is not accessed for two cycles or more, that block is discarded.

FIG. 7B shows the flow of processing when a write request (write request) from the address generator 43 is generated.
In the present embodiment, the write access occurs when the read data is rewritten and written back to the same address, so the same address is read immediately before, and no cache miss occurs. Therefore, after a write request is generated (S20). It is not determined whether a cache hit or a miss hit.

Write request data is stored in the corresponding block of the data storage section 46 (S21), and TTL = 4 and dirty = 1 are set (S22).
In step S22, TTL = 4 is set. This is because, if a write access does not occur for two or more cycles after the write occurs, the data in the block is written back to the memory, and an access for two or more cycles is performed. If it does not occur, the block is discarded.

FIG. 7C shows the flow of processing for each ink ejection timing given from the recording head controller 35.
After the ink ejection timing occurs (S30), TTL (Time To Live) is set for all safe blocks.
If writing does not occur for a certain period, the data in the data storage unit 46 is written back to the memory 12 (flash operation). If no access occurs for a certain period, the block is discarded, and then a cache miss occurs. Be available when

  If TTL> 0, the TTL set by the read / write access is counted down every time the ink ejection timing occurs (S31).

After the countdown, it is determined whether TTL == 2 and dirty == 1 (S32).
For the block in which TTL == 2 and dirty == 1, that is, the block for which two-cycle write access has not occurred after the previous write access, the data in the data storage unit 46 is written back to the memory 12 (S33). , Dirty is cleared to 0 (S34).

For blocks where TTL == 2 and dirty == 1, it is determined whether TTL == 0 and dirty! = 1 (S35).
By clearing enable to 0 for blocks where TTL == 0 and dirty == 0, that is, blocks for which no 2-cycle read access or write access has occurred since the previous read access or flash operation, The block is released (S36).

  In this embodiment, the control using enable is described in step S36. However, the control using enable and not using enable and using a block with a minimum TTL and dirty = 0 when a mishit occurs is also possible. Good.

Next, the difference in memory transfer rate due to the block arrangement of the divided image data will be described with reference to FIG.
FIG. 8A shows an aspect in which the blocks are arranged in a lattice pattern, and FIG. 8B shows an aspect in which the blocks are arranged in a staggered pattern.
In FIG. 8A and FIG. 8B, the position of the recording head is H1 at the Nth discharge (N is an integer equal to or greater than 0), H2 at the N + 1th discharge, and N + 2th discharge. The hour position is indicated by H3.

  In FIG. 8A, when the recording head is moved from the H1 position to the H2 position, the necessary memory access is the B2 area, and reading for four blocks is newly required.

  On the other hand, in FIG. 8B, when the recording head moves from the H1 position to the H2 position, the necessary memory access is the B2 area, and it is necessary to newly read two blocks. Further, when the recording head moves to the position H3, it is necessary to newly read out two blocks indicated by B3. In this way, the number of memory accesses per drive cycle can be reduced.

  The memory divided so as to have a staggered arrangement can reduce the maximum number of blocks that need to be newly read for each drive cycle, and the boundary between consecutive blocks is not a straight line, The required transfer rate can be reduced.

  By arranging the blocks in a substantially square shape and in a staggered arrangement, the change in the number of blocks that need to be secured in the data storage unit 46 as a sub-memory due to the inclination of the recording head 19 is small, and as a result, the data storage unit 46 The required capacity is minimal.

DESCRIPTION OF SYMBOLS 10 Printing apparatus 12 Memory 13 Control part 19 Recording head 21 CPU
32 Image reading unit (rotator)
45 Table management section (sub-memory management means)
46 Data storage unit (sub memory)
70 print media 80 users

JP 2010-520087 A

Claims (10)

A printing apparatus that performs printing by moving on a print medium,
A recording head capable of simultaneously recording a plurality of pixels;
Position information calculating means for obtaining the current position and inclination of the recording head;
A memory for storing image data of an image to be printed by the recording head;
A control unit having image reading means for reading out necessary pixel data from the memory based on the position information of the recording head calculated by the position information calculating means and outputting the data to the recording head;
The image data stored in the memory is divided into rectangular or substantially square blocks including a plurality of pixels in at least the vertical and horizontal directions,
The image reading means associates the sub-memory for temporarily storing image data in units of blocks with the positional information of the recording head and the image data in units of blocks, and the memory for reading or writing necessary image data And a sub memory management means for managing access to the printing apparatus.   The image reading means includes means for writing back information indicating that an image of a predetermined area has been recorded into the memory in units of pixels, and records pixels in the area of the recorded image based on the information. The printing apparatus according to claim 1, further comprising: a unit that controls the recording head so that the recording head does not.   Means for writing back information indicating that the image of the predetermined area has been recorded into the memory in units of pixels; means for clearing the memory of the recorded image data; and information indicating recorded separately from the image data The printing apparatus according to claim 2, wherein the printing apparatus is any one of a unit that records the information.   The sub-memory management unit adds a TTL that is information indicating the lifetime for each block of the image data, sets the TTL by read and write access, counts down the TTL at a predetermined timing, and the TTL is constant. 4. The printing apparatus according to claim 1, wherein data is discarded or written back to the memory from a block that has reached the value of 4. 5.   5. The printing apparatus according to claim 4, wherein the TTL managed by the sub memory management unit is set such that a threshold value for writing back from the sub memory to the memory is equal to or greater than a value set at the time of reading. .   5. The TTL managed by the sub memory management unit is set so that a value set at the time of writing exceeds a value obtained by adding 1 to a threshold value for writing back to the memory from the sub memory. Or the printing apparatus of 5.   5. The TTL managed by the sub-memory management unit is set so that a value set at the time of reading exceeds a value obtained by adding 1 to a threshold value used for determination of block discard. 7. The printing apparatus according to any one of 6.   8. The printing apparatus according to claim 1, wherein the image data stored in the memory is divided into blocks having the same number of pixels in the vertical direction and the number of pixels in the horizontal direction.   9. The printing apparatus according to claim 1, wherein the image data stored in the memory is divided into blocks arranged in a zigzag pattern.   A printing system comprising: the printing apparatus according to claim 1; and an electronic device that transmits image data to the printing apparatus.