JP2895485B2 - Video memory controller used for printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a video memory used in a high-speed recording device such as a laser printer, and more particularly, to printing by improving the efficiency of the memory. The present invention relates to a control device for increasing the speed. "Conventional technology" To achieve higher printing speed and higher resolution than before,
Image data corresponding to one page is stored as image data in a video memory such as a video RAM, and is printed out based on a print command for each page. Recording apparatuses are known, and in this type of apparatus, generally, a configuration in which the entire recordable area of a sheet is stored as image data,
In other words, a margin area (lower margin) on the lower side of the actual formed image is stored as white data as well as the area to be recorded as image data, so that a problem remains in terms of memory usage efficiency. Further, in a printer using such a memory, as shown in FIG. 3 (a), regardless of the presence or absence of the lower margin area, the time required to store the entire recordable area of the paper in the memory, The time for outputting (printing) the image data of the entire recordable area recorded in the printer must always be repeated at regular time intervals, and there is still a problem in increasing the printing speed. In such a printer having such a configuration, there are many cases in which, for example, A-4 size and legal size papers whose only paper lengths are different from each other are selected for printing. Must be adjusted to the longer one, so that the printing time becomes more redundant. In order to solve such a drawback, for example, as shown in FIG. 4, the length of each sheet of different size is set in advance as constants 51 and 52, and it is attempted to print out of the plurality of constants 51 and 52. Multiplexer that matches the paper size
A horizontal synchronizing signal for detecting a dot line for each scan including white data (margin area data) which is input to one side of the comparator 54 via the 53 and output to the paper side from the video memory and completes printing is output. There is a video memory control method in which the value counted by the counter 55 is input to the other side of the comparator 54 and output from the memory is performed until the contents match. "Problems to be Solved by the Invention" According to such a control method, by setting the paper length constants 51 and 52 according to the paper type, the output control of the video memory corresponding to the paper size is performed. The print cycle can be adjusted to each paper size, and the second problem that the print cycle has to be adjusted to the longer paper size can be solved. However, the video memory contains white data (margin area data). If the image data is not output, it is impossible to match the above-mentioned paper length constant, and it is impossible to increase the printing speed when the lower margin is included. The present invention is configured to be able to store the actual image data of the next page in the memory immediately after outputting the actual image data that does not include the lower margin area existing on the corresponding page, in order to solve the disadvantages of the related art, Accordingly, it is an object of the present invention to provide a video memory control method which aims at efficient use of the video memory, shortens the print cycle accordingly, and further speeds up the print quality. "Means for Solving the Problems" A CPU (Central Processing Unit) is used in a controller for performing print control of a high-speed printer to which the present invention is applied. The focus is on not only being able to judge the contents of the data, but also being able to judge the row address corresponding to the last row of the actual image data not including the lower margin area stored in the video memory. That is, the present invention provides a video memory 1 that stores actual image data not including a lower margin area, a CPU 3 that determines an address value corresponding to a row address of a last row of the image data stored in the memory 1, A latch means 22 for setting and holding the last row address value transmitted from the CPU 3, a counter 23 for sequentially counting up a row address of the data from the reset state when the image data is output from the video memory 1, and a counter 23 for counting the count value. Comparing means 24 for comparing the last row address value held by the latch means 22; and when the two data match, a signal to the video memory 1 is sent to the video memory 1 based on a signal output from the comparing means 24. After releasing the write-protection of the image data, the printer side conveys the paper and the lower margin area in parallel with the writing of the image data of the next page in the video memory. Rights performed continuously optical scanning to obtain a synchronization signal, and is characterized in that performed by the bottom margin setting corresponding to the sheet length based on the horizontal synchronizing signal. According to such technical means, the video memory 1 does not store the entire recordable area of the paper, but stores only the actual image data excluding the lower margin area. As well as efficient use,
Since the image data of the next page can be stored during the setting of the lower margin area after the actual image data printing is completed (while the paper is being conveyed), the print cycle time can be greatly reduced as a result. According to the technical means, the write-protection of the image data to the video memory 1 is released simultaneously with the completion of the actual image data printing, and the actual image data of the next page is stored. The cycle is determined by the length of the actually printed image data in the row direction regardless of the paper size. As a result, even when a long paper is used, the print cycle time does not needlessly become redundant. Thus, a print cycle time corresponding to the actual image length of each sheet can be obtained. Therefore, according to the present invention, if the video memory 1 having a capacity corresponding to the maximum paper length is prepared, the CPU 3 only needs to perform storage and output control of image data corresponding to each paper length. The burden is reduced, and it is not necessary to set a constant in advance according to the type of paper as in the above-described conventional technology. As a result, it is possible to arbitrarily use a paper having a free paper length, thereby improving versatility. I do. Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just FIG. 1 is a block diagram showing a control section of a laser printer according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an internal configuration of a data control circuit 2 of a video memory 1 incorporated in the control section. In FIG. 1, the portion "a" indicated by an imaginary line in the figure is the printer main body, and the laser beam oscillated from the laser diode 11 is deflected in the main scanning direction by the polygon mirror 12 on the photosensitive drum (not shown). An optical scanning system for transmitting a horizontal synchronizing signal for each scanning (dot) line to the data control circuit 2 on the controller side by a photodiode 13 (signal detecting means) arranged on the deflection start position while performing optical scanning; An electrophotographic section (not shown) for developing a latent image written on the photosensitive drum by the optical scanning, transferring the toner image to a sheet conveyed to a transfer position, and fixing the toner image on the sheet; However, since such a configuration is not a main part of the present invention, detailed description thereof will be omitted. On the other hand, the part "b" indicates the internal configuration of the controller, and the CPU 3 performs predetermined arithmetic control processing based on an instruction from the host computer, the printer control circuit 5, the data control circuit 2, and the input from the host computer to the CPU 3 side. Each line of the actual image data that does not include the
Column address (including the row address corresponding to the last row)
And the like, an external memory 6 for storing data, etc., an interrupt circuit 4, a video memory 1 for storing image data in a built-in memory cell, a serial register 7 for converting the image data into serial data, an interface 8, and the like. I have. Next, the printer control circuit 5 transmits a paper feed signal to the printer “A” based on the print drive signal transmitted from the CPU 3 to start transporting the paper, A polygon mirror based on the laser drive signal transmitted through the data control circuit 2
A laser beam is oscillated from the laser diode 11 while rotating the laser diode 12 to perform predetermined optical scanning, and the photodiode 13 transmits a horizontal synchronization signal for each scanning (dot) line to the data control circuit 2. And then,
When a print instruction signal is input from the CPU 3 to the printer control circuit 5, the image data in the video memory 1 is serially converted by the serial register 7 through the data control circuit 2 while the laser beam output from the laser diode 11 is converted. The modulation is performed, and a predetermined image is written on the paper side via the electrophotographic unit. When the print instruction signal is transmitted from the CPU 3 and the actual image data is output from the video memory 1, the interrupt circuit 4 inhibits writing of the image data to the video memory 1 and is in a non-printing state. The write prohibition is released when a match signal is output from a comparator 24 described later in the data control circuit 2. Next, the main internal configuration of the data control circuit 2 as the gist of the present invention will be described. A control unit 20 includes various control signals such as read / write and print instruction signals transmitted from the CPU 3, various address strobes generated in the control unit 20, a row / column switching signal, a reset signal, and a comparator 24. More match signal,
Based on the video clock signal and the horizontal synchronizing signal, the video memory 1 and the control circuit 2 can be transmitted at predetermined timing to respective elements described later. 21 is for controlling the row / column address information from the CPU 3 to the control 20
A multiplexer for transmitting to the video memory 1 in a time-sharing manner based on the row / column switching signal transmitted from the
Via the U3 address line or data line
A latch circuit 22 for setting and holding a value corresponding to the last row address of actual image data in the column address information. Reference numeral 23 denotes a row counter, which is configured to be resettable based on a reset signal from the control unit 20 before or simultaneously with the output of image data from the video memory 1, and from the reset state based on a horizontal synchronization signal. 1
Each time one line of image data is output, the row address is sequentially counted up. Reference numeral 24 denotes the count value in the row counter 23 and the latch circuit 22.
A comparator for comparing an address value corresponding to the last row of the actual image data held in the interrupt circuit 4 when the two data coincide with each other via the control unit 20 . Numeral 25 denotes a digit counter, which counts up by a command from the control unit 20 for each bit number corresponding to one word, and designates a word for one line. Next, the operation procedure of this embodiment will be described. (STEP 1) Image data storage WRIT output from CPU3 using the address signal of CPU3
Using the E signal, the row / column address strobe generated by the control unit 20, and the row / column address switching timing signal, actual image data not including the lower margin area of the memory cell in the video memory 1 is stored. (STEP 2) Address value setting of latch circuit 22 After image data is stored in video memory 1, a row address value corresponding to the last row of image data to be printed stored in video memory 1 is set in latch circuit 22. Hold. (STEP 3) Image data output After the printer is driven, the image data stored in the video memory 1 is output to the printer “A” via the control unit 20 based on the print instruction signal from the CPU 3, and the image data is output. An image corresponding to the image data is printed, and a row address corresponding to the image data is sequentially counted from the reset state by the row counter 23 based on the horizontal synchronization signal during the printing. (STEP 4) Completion of image data output The comparator 24 compares the count value with the last row address value held in the latch circuit 22, and interrupts a match signal indicating that both data match via the control unit 20. The video signal is transmitted to the circuit 4 side, the interruption circuit 4 informs the CPU 3 side that the video output is completed, and the interruption of the interruption circuit 4 is prohibited, and the next page transmitted from the CPU 3 via the video data control circuit 2 is transmitted. The image data is sequentially stored in the video memory 1 side. (STEP 5) Setting of lower margin Even after the output of the video memory 1 is completed,
Since the printer drive signal is continuously transmitted to the printer control circuit 5, the paper conveyance and the output of the horizontal synchronization signal are continuously performed on the printer "A" side in parallel with the storage of the image data of the next page. When the horizontal sync signal corresponding to the entire recordable area corresponding to the paper size and the corresponding
The U3 side transmits a sheet break signal, and the next sheet is conveyed to the transfer standby position of the electrophotographic section on the printer “A” side. Then, after the data storage is completed, the process returns to (STEP 2), and this is repeated thereafter. According to this embodiment, in the prior art, as shown in FIG. 3A, the operation of storing the entire recordable area of the paper in the memory 1 irrespective of the presence or absence of the lower margin area (time B). (A) to output (print) the image data of the entire recordable area stored in the memory 1
(Time) are performed alternately, so that a constant print cycle time (A + B) is always required even if the lower margin area is present or the paper size is different. In the case of this embodiment, FIG. When there is a lower margin area or the like as shown in (1), the image memory is used as the time (C) for outputting the image data stored in the image memory 1 for the set time (C) of the lower margin area. As a result, the operation time B stored in the memory 1 can be reduced by that much, and as a result, the print cycle time (A + BC) can be reduced by the length of the operation time. As a result, the above-described operation of the present invention is smoothly achieved, and the storage time of the image memory not including the lower margin is sufficient, and the image data of the next page can be stored earlier by the output time of the lower margin. Therefore, the print cycle can be shortened accordingly. [Effect of the Invention] As described above, according to the present invention, the actual image data of the next page is stored in the memory 1 immediately after outputting the actual image data that does not include the lower margin area existing on the corresponding page. As a result, the video memory 1 can be used efficiently, and the printing cycle can be shortened accordingly, and the printing speed can be further increased.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a control section of a laser printer according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an internal configuration of a data control circuit of a video memory incorporated in the control section. It is. FIG. 4 is a block diagram showing a control device of the video memory 1 according to the prior art. FIG. 3 is a time chart showing a print cycle of the prior art and the embodiment of the present invention.

Claims (1)

(57) [Claims] A video memory for storing actual image data not including the lower margin area, a central processing unit for determining an address value corresponding to a row address of a last row of the image data stored in the memory, Latch means for setting and holding the transmitted last row address value, a counter for sequentially counting up the row address value of the data from a reset state when the image data is output from the video memory, and holding the count value and the latch means Comparing means for comparing the final row address value thus obtained, based on a signal output from the comparing means when the two data coincide with each other,
After releasing the prohibition of the writing of the image data to the video memory, in parallel with the writing of the image data of the next page in the video memory, the printer side obtains the horizontal synchronizing signal for the sheet conveyance and the lower margin area on the printer side. A video memory control device for continuously performing optical scanning and setting a lower margin corresponding to a sheet length based on the horizontal synchronization signal.