Raster scan type printer

Abstract

 In a raster scan type printing device, capable of executing a printing operation on both surfaces of a printing medium, comprising storing unit for storing a plurality of codes corresponding to the data to be printed, and printing device for printing the data on said printing medium, further provided are unit for selecting a predetermined surface of said printing medium on which a printing operation is executed; and unit for controlling the codes stored in said storing unit so as to be rearranged at least in a column direction in case that said predetermined surface of said recording medium is selected by said selecting unit. Thus, when a reversing operation, for reversing the addresses of codes corresponding to the data to be printed in a back side printing mode, is executed, a hardware structure, using an address conversion circuit in the address bus for the image buffer where bit data are written, reduces a load applied to a software and shortens an operating time required for the reversing operation.

Description

[0001] The present invention relates to a raster scan type printer capable of executing printing operations on both surfaces of a printing medium.

[0002] When a double side printing operation is performed using a printing apparatus such as a laser printer, character and graphic images may be horizontally or vertically reversed on one surface of a printing medium, for example, a printing sheet. The images to be printed are electrically formed on a so-called page memory by means of software or dedicated hardware. The resultant images are written in an image buffer every bit and output to a printing mechanism section in which printing operations are executed. The above structure has been well known and utilized.

[0003] However, the above method causes the software to be complicated, further the printing time to be increased, or the dedicated hardware to increase the production cost.

[0004] It is therefore an object of the invention to provide an improved raster scan type printer with both surface printing function capable of simply executing a reversing operation of the data to be printed on the back surface.

[0005] For this purpose, according to the present invention, there is provided a raster scan type printing device, capable of executing a printing operation on both surfaces of a printing medium, comprising storing means for storing a plurality of codes corresponding to the character and/or symbol data to be printed, and printing means for printing the data on said printing medium, said printing device further comprising:
selecting means for selecting a predetermined surface of said printing medium on which a printing operation is executed; and
controlling means for controlling the codes stored in said storing means so as to be rearranged at least in a scan direction when said predetermined surface of said recording medium is selected by said selecting means.

[0006] The invention will be better understood from the following description which is given by way of example only with reference to the accompanying drawings in which:

FIG. 1 is a block structural diagram of a raster scan type printer with both surfaces printing function embodying the present invention;

FIGs. 2A, 2B are diagrams showing the data storage state in an image buffer viewed from a controlling unit of the printer according to the present invention;

FIGs. 3A, 3B are diagrams showing the reverse state of addresses of data to be printed on the back surface of a printing medium and data for one raster to be printed on both front and back surfaces; and

FIGs. 4A, 4B, and 4C and FIGs. 5A, 58, and 5C are conceptual diagrams showing the reverse states of an image corresponding to the front and the back surfaces, respectively.

Description of the Embodiments

[0007] FIG. 1 shows a block diagram of a raster scan type printer with both surfaces printing function embodying the present invention.

[0008] As illustrated in FIG. 1, the printer embodying the present invention is structured by an interface 2 for inputting code corresponding to the character and/or graphic data to be printed from an external host computer 1, a CPU (Central Processing Unit) 3 for controlling the entire printer when the data are inputted into the printer through the interface 2, a receiving buffer 4 for temporarily storing data codes having been inputted, a RAM (Random Access Memory) as a page memory 5 for storing the data every page, a ROM (Read Only Memory) 6 for storing a system control program, a CG (Character Generator) 7 for storing bit data such as characters according to codes, a DPRAM (Display RAM) as an image buffer 8 for storing image information according to the data written and stored in the page memory 5, a parallel-serial conversion circuit 9 for converting parallel output data from the DPRAM 8 into serial output data, a printing mechanism section, i.e., an engine 10 composed of a laser scanner and so forth for inputting bit data for one scan from the parallel-serial conversion circuit 9 and for printing the data on a sheet, and so forth.

[0009] The CPU 3 and the DPRAM 8 are electrically connected by a data bus 11, an address bus 12, and a control bus, not shown. Between the CPU 3 and the DPRAM 8, an address reverse circuit, i.e., address conversion circuit, 13 composed of an inverter 13-1 and an address selector 13-2 are disposed therein. To the address reverse circuit 13, a front/back surfaces printing selection signal "S" is input from the CPU 3 through an address decoder 14 and an operation is switched. For the front surface, the address data, transmitted through a line indicated by a letter "F" in the drawing, which is not reversed is output. For the back surface, the address data, transmitted through a line indicated by a letter "R", which is reversed via the inverter 13-1 is output. When the printing operations are executed on the back surface of the sheet, the column addresses representing the horizontal addresses in a predetermined data unit are horizontally reversed when the writing operations from the page memory to the DPRAM 8 are executed by every bit.

[0010] In addition, the above address decoder 14 as a transfer address change circuit for changing transfer addresses which are output from the CPU 3 and a timing generation circuit 15 for generating timing signals for the DPRAM 8 are respectively provided. To the address decoder 14, the address signal and the front/back surface printing selection signal "S" are input from the CPU 3. The timing generation circuit 15 receives a transfer signal "T1" which is output from the address decoder 14 and outputs a predetermined DPRAM control timing signal "T2" to the DPRAM 8. The DPRAM control timing signals are chiefly classified as four types of signals, i.e., a write signal, a read signal, a transfer signal, and a refresh signal.

[0011] On a data line between the DPRAM 8 and the parallel-serial conversion circuit 9, a data reverse circuit 16 for reversing data every bit for back surface printing data is provided. The data reverse circuit 16 receives the front/back surface printing selection signal "S" and a printing operation state is switched between the data forward connection and the data reverse connection as hardware. In the present embodiment, the column addresses representing horizontal address data for the back surface are horizontally reversed every word including successive 16 bits (D0 through D15) data in one raster.

[0012] By referring to FIGs. 2A and 2B, an operation of the data storage area of the DPRAM 8 for the front/back surface data in the CPU 3 is described hereinafter. Transfer address sections "a" and "b" for the front surface and the back surface operate in the manner that when some data are written to an address of the transfer address section from the CPU 3, the timing generation circuit 15 reads the address and the printing data for one raster according to the address is transferred from the DPRAM 8 to the parallel-serial conversion circuit 9.

[0013] As illustrated in FIGs. 2A and 2B, the data address being output from the CPU 3 is set so that the front surface printing data storage area "A" and the back surface printing data storage area "B" are separately written to the row addresses and the column addresses of the DPRAM 8, respectively. Therefor, the storage locations of the transfer address sections "a" and "b" are set so that they differ in the respective printing data storage areas in the column address direction. Thus, the transfer address sections "a" and "b" viewed from the CPU 3 differ in the column address direction.

[0014] In the above structure, the CPU 3 writes bit data to predetermined addresses of the DPRAM 8 according to page data, including address data, stored in the page memory 5. In addition, the DPRAM 8 reads one scan of data, for example, data for 4096 dots, according to the transfer addresses of the image bit data written in the DPRAM 8 according to predetermined address data and transfer signals from the CPU 3 and transfers the resultant data to the engine 10 via the parallel-­serial conversion circuit 9, thereby printing the data to a predetermined position on the sheet.

[0015] Image information is transferred from the DPRAM 8 to the engine 10 by assigning a predetermined address by the CPU 3 and by the timing signal "T2" which is output from the timing generation circuit 15 according to the transfer signal "T1" from the address decoder 14 according to the front/back surface printing selection signal "S". In other words, depending on whether the printing surface assigned by the CPU 3 is the front surface or the back surface, one of the transfer address sections "a" and "b" is set to the address decoder 14. The address decoder 14 determines whether the data is a transfer command or not in accordance with the address data being read and the transfer address currently set. When the data is the transfer command, the address decoder 14 outputs the transfer signal "T1" to the timing generation circuit 15. After that, the timing generation circuit 15 outputs the signal "T2" to the DPRAM 8 in a predetermined timing.

[0016] In this manner, in the case that the selection signal "S" from the CPU 3 represents the front surface, the address decoder 14 outputs the transfer signal "T1" only when an address of the transfer address section "a" is assigned. On the other hand, in the case that the selection signal "S" represents the back surface, the address decoder 14 outputs the transfer signal "T1" only when an address of the transfer address section "b" is assigned.

[0017] FIGs. 3A and 3B show the condition where transfer addresses are reversed and printing data is reversed in one raster in the CPU 3, the DPRAM 8, and the engine 10. In the case of the conventional A4 sheet size, on the front surface viewed from the CPU 3, the printing data area is set to the left of one raster including 4096 dots, wherein dots 0 through 15: non-image portion; dots 16 through 2415: image portion; and dots 2416 through 4079: non-image portion. The transfer address section "a" is set to the right end, dots 4080 through 4095. On the other hand, on the back surface, as described above, the addresses are reversed between the CPU 3 and the DPRAM 8 by the address reverse circuit 13. Therefore, the printing data storage area "B" and the transfer address section "b" of the back surface are set to the reverse locations of the front surface. In other words, the addresses of the DPRAM 8 are reversed in the column direction, i.e., horizontal direction in each of 16-bits data by means of the address reverse circuit 13 constituted by a predetermined hardware arrangement. In addition, as shown in FIG. 3B, the back surface data are horizontally reversed between the DPRAM 8 and the engine 10 by the data reverse circuit 16 every 16 bits.

[0018] FIGs. 4A, 48 and 4C and FIGs. 5A, 5B and 5C show a conception of reversal of address data on the front surface and back surface at the page memory 5, the DPRAM 8, and the engine 10. The drawings show an example where each character is composed of 32 x 32 dots. In the page memory 5, characters are actually stored in the form of code data. As illustrated in FIGs. 5A through 5C, for the data on the back surface, the storage locations of the data transferred from the CPU 3 to the page memory 5 are vertically reversed every character. When data are transferred from the page memory 5 to the DPRAM 8 every bit, the row addresses are vertically reversed every raster. This operation is performed by program software in the present embodiment. In addition, the column addresses are horizontally reversed by the address reverse circuit 13 every 16 bits. When the data are output from the DPRAM 8 to the engine 10, the 16 bit unit is horizontally reversed every bit by the data reverse circuit 16.

[0019] As described above, according to the present embodiment, since the CPU 3 synchronizes with the transfer signal which is output depending on whether the printing surface is the front surface or the back surface and a predetermined address being assigned, it outputs each address of the transfer address section "a" for the data of the front surface to the engine 10 and that of the transfer address section "b" for the data of the back surface to the engine 10 only at a predetermined time, thereby preventing the data being mistakenly transferred. In other words, it is not necessary for the CPU 3 to reverse the addresses in the column direction, only necessary to designate addresses of the DPRAM 8 even if a printing operation is executed on the back surface. The address conversion operation in the column direction are executed by means of a circuit including the address reverse circuit 13. Therefore, an arrangement of the software controlled by the CPU 3 can be simplified.

[0020] In addition, the data from the DPRAM 8 is serially converted every 16 bits by the serial-parallel conversion circuit 9 via a forward connection or a reverse connection structured by hardware of the data reverse circuit 16 and then output to a controller of the engine 10. If such 16 bit data is assigned by software, a shift operation should be executed 16 times, resulting in taking a long process time. Since this operation is executed by hardware, without using complicated software, the operation time can be remarkably reduced.

[0021] In the present embodiment, the vertical reverse operation is conducted by a program of the CPU and the horizontal reverse operation every bit in the predetermined data unit is conducted by the data reverse circuit 16. These means can be also accomplished in different structures according to the present invention.

Claims

1. A raster scan type printing device, capable of executing a printing operation on both surfaces of a printing medium, comprising storing means for storing a plurality of codes corresponding to the character and/or symbol data to be printed, and printing means for printing the data on said printing medium, said printing device further comprising:
selecting means for selecting a predetermined surface of said printing medium on which a printing operation is executed; and
controlling means for controlling the codes stored in said storing means so as to be rearranged at least in a scan direction when said predetermined surface of said recording medium is selected by said selecting means.

2. The printing device according to claim 1, wherein said controlling means includes address designating means for designating addresses for each of said codes, saving means for saving bit map data corresponding to said codes having been stored in said storing means, and address converting means for converting the addresses designated by said address designating means in a predetermined manner when said bit map data are saved in said saving means, when said predetermined surface is selected by said selecting means, whereby each of the codes stored in said storing means are rearranged by means of the conversion operation executed by said address converting means.

3. The printing device according to claim 2, wherein said address converting means is provided between said saving means and said address designating means.

4. The printing device according to claim 2 or 3, wherein said address converting means reverses the addresses included in each raster in said scan direction.

5. The printing device according to claim 2, 3 or 4, which further comprises another address converting means for converting at least the addresses designated by said address designating means in a row direction perpendicular to said scan direction when bit map data corresponding to said codes having been stored in said storing means are saved in said saving means.

6. The printing device according to claim 4 or 5, wherein the codes corresponding to said one raster comprises a print code for printing dots on said printing medium and non-print code located immediately before and after said print code.

7. The printing device according to claim 2, 3, 4, 5 or 6 wherein said address converting means reverses the addresses of every predetermined number of bits and reverses the addresses of each of the bits in each said predetermined number of bits, said reversing operation of said each of the bits being executed by means of a predetermined electrical circuit.

8. The printing device according to claim 7, wherein said predetermined number comprises 16.

9. The printing device according to any one of claims 2 to 8 wherein said address converting means includes an inverter circuit.

10. The printing device according to any one of claims 2 to 9 wherein said storing means includes a character generator for storing bit data corresponding to said each of stored codes, whereby the bit data, corresponding to the codes whose addresses are designated by said address designating means, being read out and restored in said saving means in accordance with the addresses converted by said address converting means.

11. A raster scan type printing device, capable of executing a printing operation on both surfaces of a printing medium, comprising storing means for storing a plurality of codes corresponding to the character and/or symbol data to be printed, and printing means for printing the data on said printing medium, said printing device further comprising:
bit map memory means for saving the codes having been stored in said storing means as a bit map corresponding to said codes;
selecting means for selecting a predetermined surface of said printing medium on which a printing operation is executed;
address designating means for designating addresses for each of said codes;
address converting means, provided between said bit map memory means and said address designating means, for converting the addresses designated by said address designating means in a predetermined manner in a scan direction when said codes having been stored in said storing means are saved in said bit map memory means, when said predetermined surface of said recording medium is selected by said selecting means; and
another address converting means for converting at least the addresses designated by said address designating means in a row direction perpendicular to said scan direction when said codes having been stored in said storing means are saved in said bit map memory means, when said predetermined surface of said recording medium is selected by said selecting means.

12. The printing device according to any preceding claim, wherein said predetermined surface of said recording medium comprises a back side surface.

Drawing