GB2117151A - Method and apparatus for dot pattern print control - Google Patents

Abstract

A method and apparatus for dot pattern print control in a printing apparatus in which dot pattern data stored in a storage means is read out in response to print data transferred from a host machine, a dot pattern being printed out in response to the dot pattern data. A print position is designated by the print data at a desired pitch. One of the dot pattern data which corresponds to the specified pitch is read out of the storage means, so that a dot pattern is printed out on the basis of the output pattern data. When the print data commands overlay printout, at least two groups of dot pattern data are read out of the storage means and combined. A dot pattern is printed out in response to the composite dot pattern data. Based on the content of one dot pattern data, part of the other dot pattern data is combined with the former to reproduce a well proportioned composite dot pattern. <IMAGE>

Description

SPECIFICATION Method and apparatus for DOT pattern print control Background of the invention The present invention relates to a method and apparatus for controlling the printout operation. of characters, marks and the like (represented by characters hereinafter) in the form of dot matrixes. The present invention is applicable to dot printers of the ink jet type and laser type, for example.

In an impact printer, desired one of line feed pitches of 1/8", 1/6", 1/4" and their integral multiples may be selected. Also available are the line feed pitch of + 6" for printing out superscripts and subscripts in the case of the 1/8" line feed pitch, and the line feed pitch of +1/12" for printing them out in the case of 1/6" line feed pitch. The superscripts and subscripts are printed out on an imaginary line which is shifted one half the basic line feed pitch and may be typified by those of algebraical expressions such as n4 and Aa as well as those of chemical expressions such as Fe2O4 and H202.

Meanwhile, difficulty is generally experienced in controlling the line feed to a desired width in a raster scan type non-impact printer.

Improvements in the raster scan type nonimpact printer have been proposed in Japanese Patent Publication No. 54-364/79 and Japanese Patent Application Nos. 56-186624/81 and 56186625/81. None of these proposals is fully acceptable, however.

An ordinary serial impact printer can print out characters with, for example diacritics "' " and " ", " "', " " and " " " or vertical or horizontal rules either by stopping or backspacing a print head. Such a special kind of characters will hereinafter be referred to as "overlay" characters each consisting of overlaid character and diacritic or the like. Overlay characters cannot be printed out by a printer whose print head has to run at a predetermined speed without stopping or backspacing, e.g. ink jet printer. One approach for the printout of overlay characters in the ink jet printer, for example, may be causing the print head into two repeated runs on the same line one of which is to print out a desired character and the other to print out a mark or the like associated therewith.

This, however, lowers the average printout rate because the time period necessary for the printout of one line is doubled. Another approach may be preparing additional overlaid dot matrixes for overlaid characters in the event of arranging dot matrixes of characters, and allocating specific character codes to the overlaid dot matrixes. A drawback in the second approach is that the available combinations of the overlaid characters are limited; an increase in the number of overlaid dot matrixes would increase the capacity of a pattern memory. In an impact line printer or the like, a composite character or a figure is generated by preparing a desired form printed in advance and printing out only a figure thereon by the printer. A laser printer, for example, is capable of printing out a form simultaneously with characters and figures.Three different methods are available for so printing out a form in the prior art laser printer or the like: a method which overlays the form optically using a microfilm or the like, a method which overlays the form relying on an image buffer having a capacity of one page of dot data, and a method which picks up an X-Y dot position as a target insertion position in the event of printing and overlaying it by hardware.

All these methods, however, require quite intricate constructions and arrangements.

Efforts have heretofore been made to overcome the drawbacks discussed above as disclosed in Japanese Patent Laid-Open Publication No. 53-112037/78 and Japanese Patent Application No. 56-214589/81. However, they are not satisfactory in various respects.

Summary of the invention It is an object of the present invention to permit a line feed to occur at any one of various pitches in dot pattern print control.

It is another object of the present invention to effect such a desired line feed with a simple control and without increasing the number of hardware components.

It is another object of the present invention to facilitate overlay printing without any incresae in memory capacity.

It is another object of the present invention to improve the quality of overlay printing and thereby afford well proportioned overlaid characters.

It is another object of the present invention to provide a generally improved method and apparatus for dot pattern print control.

In accordance with the present invention, a method and apparatus for dot pattern print control in a printing apparatus is disclosed in which dot pattern data stored in a storage means is a read out in response to print data transferred from a host machine, a dot pattern being printed out in response to the dot pattern data. A print position is designated by the print data at a desired pitch. One of the dot pattern data which corresponds to the specified pitch is read out of the storage means, so that a dot pattern is printed out on the basis of the output pattern data. When the print data commands overlay printout, at least two groups of dot pattern data are read out of the storage means and combined. A dot pattern is printed out in response to the composite dot pattern data.Based on the content of one dot pattern data, part of the other dot pattern data is combined with the former to reproduce a well proportioned composite dot pattern.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.

Brief description of the drawings Figs. 1 a-1 c are diagrams showing a prior art dot pattern print control apparatus; Fig. 2 is a block diagram of a print control apparatus embodying the present invention; Fig. 3 is a view of a font memory included in the apparatus of Fig. 2; Figs. 4a and 4b are diagrams respectively showing the construction of a font memory corresponding to one character and scan directions; Figs. 5a and 5b are diagrams showing the construction of a page memory shown in Fig. 2; Figs. 6a and 6b are diagrams showing data and addresses stored in the page memory of Figs. 5a and 5b; Fig. 7 is a view of exemplary character codes and control codes stored in the page memory;; Fig. 8 is a block diagram of a character generator section of Fig. 2; Fig. 9 is a block diagram showing details of a DMA counter control of Fig. 8; Figs. 1 Oa and 1 Ob are a block diagram of a font memory control section shown in Fig. 8 and a diagram of addresses associated therewith; Fig. 11 is a view of an exemplary dot pattern of a standard dot matrix construction which represents a mark to be overlaid on a character; Fig. 1 2a is a view of exemplary dot patterns of proportional space characters; Fig. 1 2b is a view of exemplary dot patterns of marks to be overlaid on characters and read out of the pattern memory each in matching relation with a proportional space character;; Fig. 1 2c is a view of dot patterns which are the combined versions of the matched dot patterns shown in Figs. 1 2a and 12b; Fig. 1 3 is a block diagram showing an example of a print system which uses a dot printer; and Fig. 14 is a block diagram of another embodiment of the present invention.

Description of the preferred embodiments While the method and apparatus for dot pattern print control of the present invention is susceptible of numerous physical embodiments, depending upon the environment and requirements of use, substantial numbers of the herein shown and described embodiments have been made, tested and used, and all have performed in an eminently satisfactory manner.

To facilitate understanding of the present invention, a reference will be made to prior art dot pattern print control apparatuses, depicted in Figs. 1a-1c.

Referring to Fig. 1 a, the prior art apparatus includes a dot memory for accommodating figures and causes them to be printed out after rearrangement. In detail, the control system includes a page memory 10 into which character and/or figure codes fed from an external CPU are written in the order to be printed out. These codes are read out of the page memory 10 timed to a clock which is supplied from a printer 12 to the control apparatus. A font memory (character generator) 14 is addressed by the character and figure codes so that dot pattern data associated with the codes are read out thereoutof. A plurality of lines of such dot pattern data are written into a buffer memory 16, arranged therein at a desired line feed pitch, and then fed to the printer 12.The printout operation at the printer 12 continues without interruption because a string of dot pattern data read out of the font memory 14 is successively written into a second buffer memory 1 8 while the buffer memory 1 6 is delivering data to the printer 1 2.

Referring to Fig. 1 b, the printer disclosed in Japanese Patent Publication No. 54-364/79 is illustrated. The system is such that, unlike the system of Fig. 1 a, data are written into the page memory 10 necessarily after compression; if a string of characters "ABC" are followed by a blank, data "A, B, C, blank" are written into the page memory 10 and then character codes "M, N, O" on the second line just after the "blank".

Again, the dot pattern data read out of the font memory 14 are arranged by the buffer memories 16 and 18 at a desired line feed pitch and supplied to the printer 1 2.

However, both the systems shown in Figs. 1 a and 1 b suffer from a disproportionate increase in cost due to the reliance on the line buffer memories 1 6 and 18 as well as the intricate operation.

I have proposed a method which permits even an impact printer to readily print out superscripts such as A" or subscripts such as B,. In accordance with this method, a line feed control flag for printing out a character in a position shifted half a basic line feed pitch upwardly or downwardly is stored in a page memory together with a character code to be printed out (see Japanese Patent Application No. 56-186624/81). I have also proposed a method which promotes a minute line feed not only by each integral multiple of an ordinary line feed pitch but by each dot pitch and, thereby, easy arrangement of lines in one page (Japanese Patent Application No. 56186625/81). This method is attained by use of a line feed amount register which stores an amount of line feed by a unit which is smaller than an integral multiple of a basic line pitch.The method employing a line feed flag, however, is inapplicable to basic pitches such as 1/4" and 1/8" although applicable only to a basic pitch of 1/6" to print out a character shifting it one half the basic line pitch, i.e. +1/12". The method relying on the line feed register, on the other hand, results in an increase in the number of necessary hardware components as well as intricacy of control.

A prior art apparatus designed for overlay printing is illustrated in Fig. 1 c (see Japanese Patent Laid-Open Publication 53-112037/78).

Three independent code registers (buffer registers) 20, 22 and 24 are allocated to characters and marks which require overlay printout. The codes are designated one at a time by a select signal SEL1 and then fed to an address register 26. A pattern memory 28 is accessed a plurality of times so that dot pattern data are sequentially stored in a dot register 30. After a pattern is formed in the dot register 30, it is delivered to a printer 32. A problem has existed in this type of system in that the plurality of accesses to the pattern memory 28, coupled with the sequential control, slows down the operation and makes the control intricate. Where the dot matrix size differs from characters to marks as in the case of proportional space characters, it is impossible to combine them to form a composite character.Besides, the overlay printout cannot be adjusted to accommodate characters having different heights, e.g. capital and small letters.

I have proposed a print control system for a serial dot matrix printer which is designed to overcome the problem mentioned above, i.e., to promote overlay printing by a simple control without increasing the capacity of the pattern memory or slowing down the printout operation (Japanese Patent Application No. 56214589/81). A simpler control is desired for this system because an additional mark pattern memory for storing dot matrixes of marks to be overlaid is necessary and because addresses for accessing the mark pattern memory have to be independently stored in a page memory (work memory).

Referring now to Fig. 2, a print control apparatus embodying the present invention is shown in block diagram. In Fig. 2, use is made of a laser plotter or like plotter 34 which continuously prints out data by the raster scan system.

Referring now to Fig. 2, a print control apparatus embodying the present invention is shown and generally designated by the reference numeral 34. A laser plotter like plotter 36 capable of continuously printing out data on the raster scan basis is associated with the apparatus 34. An interface 38 physically connects the apparatus 36 to an external unit (data processing unit) 40. As the external unit 40 supplies a character code and a control code to the control 34, the control 34 converts a specific character code into pattern data and delivers it to the laser plotter 34 as image information.The control 34 includes a CPU 42 for controlling the entire system, a program memory 44 for storing programs, a work memory 46 for processing data, a page memory 48 which accommodates a predetermined recording area of the plotter 36, and a font memory 50 for storing image patterns which are the matches of character codes. The CPU 42, based on control codes from the external unit 40, transforms character codes into figure codes and stores them in an edited form.

The character codes and control codes supplied by the external unit 40 are the standardized codes for general use such as ASCII codes, JIS codes or EBCDIC codes. Because the page memory 48 in accordance with the present invention stores figure codes corresponding to the addresses of figure store positions of the font memory 50, the character codes are processed by the CPU 42 into figure codes as internal codes before storage.

After the storage of one page of data, the page memory 48 is released from the control of the CPU 42 via a data/address multiplexer 52 and, instead, put into DMA (direct memory access) control. A DMA counter 54, timed to a horizontal scan clock (data clock) 56 and a vertical scan clock (line sync) 58 from the plotter 36, generates an address of the page memory 48 and feeds it to the page memory 48 via an address/control bus 60, the multiplexer 52 and an address bus 62, thereby reading data (character select, font specify, etc.) out of the page memory 48. This data is applied to the DMA counter 54 and font memory 50 via data buses 64 and 66. The font memory 50 is accessed by data (bus 66) read out of the page memory 48 and a font memory address (bus 68) generated by the DMA counter 54.The resulting dot image pattern data corresponding to the character code is converted into a serial image signal by a parallel-to-serial converter or shift register 72. The serial image signal is fed to the plotter 34 via a data line 74 timed to the horizontal scan clock 56. The plotter 34 prints out data one page at a time.

A plotter connect interface 76 shown in Fig. 2 is adapted for the control over error information, sheet format information and start/stop. A line gate signal 78 determines an effective time for one main scan and a frame gate signal 80, an effective time for one page.

An address/control bus 82 and a data bus 84 each extending from the CPU 42 are connected to the multiplexer 52 and DMA counter 54 together with the work memory 46 and program memory 44. The DMA counter 54, page memory 48, font memory 50, parallel-to-serial converter 72 and multiplexer 52 constitute a character generator section, which is generally designated by the reference numeral 86 and indicated by a dotted line.

Referring to Fig. 3, the construction of the font memory included in the arrangement of Fig. 2 is illustrated. Alphabets in general use are available as 1/10" characters, 1/12" characters,1/15" characters, proportional space characters (P.S.

characters) having different widths, etc. Thus, supposing that the pixel density of the plotter 34 is 300x300 dots per inch, the dot matrix size for each character size in accordance with the present invention may be determined as follows: 1/10" character: 30x48 dots 1/12" character: 25x48 dots 1/1 5" character: 20x48 dots P.S. character: 40x48 dots, 35x48 dots, 30x48 dots, 25x48 dots, 20x48 dots, 1 5x48 dots The character matrix "M" shown in Fig. 3 represents the 40x48 dots P.S. character size; five dots, which is the smailest common multiple of the character widths, is termed "one unit".

Because one unit is five dots and the dot density of the plotter 34 is 300 dots per inch, the actual dimension of one unit is 5/300=1/60" inch.

Supposing that the largest matrix of one character is 40x48 dots, all the characters narrower than this size are put to the left in Fig. 3. All the characters have a height which is defined by 48 dots. Each eight dots are defined as one block and the entire matrix is made up of six blocks.

Hereinafter, (one unit)x(one block)=5x8 dots will be referred to as a submatrix.

The control apparatus 34 of the present invention is capable of selecting desired line feed pitch out of 1/8", 1/6", 1/4" and +1/16" and + 1/12" and, also, desired character pitch out of 1/10", 1/12", 1/1 5" and P.S., so that overlay printout is attainable with a character employed as a unit. Besides, the character output direction for printout, i.e., vertically (portrait) or horizontally (landscape), is open to choice.

In Fig. 3, P.U. stands for a pattern unit number, R.N. a ROM number, P.B. a pattern block number, and P.b. a pattern bit number.

Fig. 4a illustrates a construction of the font memory corresponding to one character, while Fig. 4b illustrates scan directions of the font memory.

The data read direction out of the matrix depends upon the orientation of a sheet on which characters are to be printed out. The orientation is either the portrait oriented vertically long or the landscape oriented horizontally long. For the portrait, the main scan will occur along the units and the subscan along the blocks as illustrated in an upper portion of Fig. 4b. For the landscape, on the other hand, the main scan will occur along the blocks and the subscan along the units as shown in a lower portion of Fig. 4b.

Suppose that the font memory 50 comprises a ROM which may be accessed by each eight bits (one byte). As shown in Fig. 4a, the dot matrix of one character is stored in five ROMs (five ROMs being shown in stacked arrangement). Because one unit, one block (5x8 dots) is stored in fragments in the five ROM's as shown in right part of Fig. 4a, an area 31 of one ROM stores eight dots which constitute one block of each unit, as indicated by dotted lines. Whether the readout direction may be the portrait or the landscape, the five ROMs are accessed at the same time to read out all the data (40 bits) of the one unit, one block submatrix and, thereafter, necessary bits are selected out of the submatrix in the portrait/landscape direction.That is, one dot is selected out of each ROM, five dots in total, for the portrait direction, while eight dots in total are selected out of one ROM for the landscape direction. Thus, the area defined by one unit and one block corresponds to one byte (bits 0-7) of each of the five ROMs (chips 1-5), whereby one character consists of 48 bytes (strictly, 64 bytesx5 chips=240 bytes (essentially, 320 bytes)). In Fig. 4a, the bytes from the 48th to 63rd are the bits which are needles for the time being and, therefore, left unused.

Assuming that each of the five ROMs has 64 kilobits, they can store 1 28 characters in total.

Figs. 5a and 5b show a construction of the page memory of the present invention.

As previously described, the CPU 42 converts character coded fed from the external unit 40 into figure codes and then store them in the page memory 48 in an edited form in response to control codes. The manner of code storage into the page memory 48 differs from the portrait orientation to the landscape orientation of a sheet. The page memory 48 is controlled with one unit width (1/60") employed as one space unit so as to have correspondence with the font memory 50.

As shown in Fig. 5a, during portrait printout, the main scan direction is the character storage direction and the maximum print area is about 8.5" corresponding to 512 spaces (1/60"x 512=8.5"). The The subscan direction is the direction along the lines and the maximum print area is 96 lines (16" in the case of a 1/6" line feed).

During landscape printout, as shown in Fig. 5b, the subscan direction is the character storage direction and the maximum print area is about 12.8" corresponding to 768 spaces (1/60"x768=12.8"). The main scan direction is the direction along the lines and the maximum print area is 64 lines (10.6" in the case of a 1/6" line feed).

Data and addresses in the page memory shown in Figs. 5a and 5b are depicted in Figs. 6a and 6b respectively. The unit for accessing the page memory is one line and one space and made up of 26 bits (one word). Hence, the total address space of the page memory is 512x96 (=768x64)=49,1 52 words.

As shown in Fig. 6a, one word comprises a string of bits for the selection of a character to be printed out (internal code; 128 characters), designation of a character font (four fonts), designation of an output unit (eight units), selection of an overlay character (internal code; 1 28 characters), designation of a font of an overlay character (four fonts), line feed control information (PLU, PLD, 1/8" LF), and underline control (UL, DUL). It will be noted that any bit whose function is needless may be omitted; for example, if the underlining function is needless, the bits 24 and 25 may be omitted to form one word by 24 bits.

As seen in Fig. 6b, the addresses of the page memory comprise 1 6 bits in total which are adapted for the control over the 48 kiloword address space. During the course of portrait printout, data are sequentially read out in the character direction so that lower nine bits constitute the space address (corresponding to 1 52 spaces) and upper seven bits, the line address (corresponding to 96 lines). During the course of landscape printout data are sequentially read out in the line direction so that lower six bits constitute the line address (corresponding to 64 lines) and upper ten bits, the space address (corresponding to 768 spaces).

Referring to Fig. 7, there is shown an exemplary manner of storing character codes in the page memory. The same editing method applies to both the portrait and landscape printout operations although the address positions for the storage are different. For the portrait printout, the main scan direction is the character direction so that a space counter (lower stage) counts spaces O--N from the left to the right. The subscan direction is the line direction so that a line counter counts lines from the top to the bottom as indicated in the leftmost part of Fig. 7.For the landscape printout, on the other hand, the main scan direction is the line direction so that the line counter counts lines from the top to the bottom as indicated in the rightmost part of Fig. 7, while the subscan direction is the character direction so that a space counter (upper stage) counts spaces O--N from the right to the left.

It will be seen that even though a unit width other than the 5-unit width (25 dots) applied to all the characters of Fig. 7 may be employed, nothing will be changed except for the increase in space width. Justification, proportional character printout and the like which are essential for a word processor, for example, can be controlled by a resolution of 1/60" (on a unit basis).

In Fig. 7, a train of characters "ABCDE" are stored in the "m" line. The data are edited such that the character "B" is shifted half a line upwardly (superscript) and the character "D" half a line downwardly (subscript). Concerning the superscript, a character code and a "PLU" control flag are set in the same space position on the line immediately preceding the current position, while the character code and a "PLD" control flag are set at the current position. Additionally, a control flag is set for the character "B" or "D" which is underlined. A "DUL" control flag is set for the character "C" which is accompanied by a double underline.

Generally, the line is fed by 1/8", 1/6", 1/4" or an integral multiple thereof. Furthermore, use is made of a 1/1 6" line feed and a 1/12" line feed; the 1/16" line feed is adapted for PLU/PLD associated with the 1/8" line feed (1/8+1/16) and the 1/12" line feed for PLU/PLD associated with the 1/6" line feed(1/6+1/1 2) and (1/6+1/12) associated with the 1/4" line feed.

In Fig. 7, the lines "m" to "m+4" are basically spaced 1/6" while the lines "M+5" to "m+8" are basically spaced 1/8". Therefore, the characters "FGHIJ" on the "m+2" line are provided by the 1/6" line feed and each of these characters comprises five units as indicated by "fro" to "F4", which are the unit nurnbers of the character font pattern. The "m+4" line is provided by the 1/4" line feed and, therefore, shifted one and a half lines relative to the "m+2" line so that it can be processed by the "PLD" and "PLD" control flags.

The "m+6" line is spaced 1/8" from the adjacent lines and, therefore, "LF" control flags are set throughout the line. In this manner, character codes are simply stored in the page memory in the case of the basic 1/6" line feed with or without the "PLU/PLD" line shift data which applies to an upward or downward half a line shift. As to the 1/4" line feed, the entire line becomes shifted half a line downwardly relative to the line 1/6" line shift so that the "PLU/PLD" line shift data is set. Further, concerning the 1/8" line feed, the line feed pitch data "LF" is set for every position of the line. It will be understood that to shift a character one and a half lines upwardly or downwardly in the case of the 1/8" line feed, both the line feed pitch data "LF" and line shift data "PLU/PLD" will be set.Thus, the line can be fed as desired at the spacings of 1/8", 1/6", 1/4", + 1/16", or + 1/12".

Referring to Fig. 8, the character generator section 86 shown in Fig. 2 is illustrated in block diagram. Synchronization for the printout operation on the page by page basis is set up by the data clock 56 and line sync 58 which are delivered from the plotter 34. The data block 56 is adapted for the synchronization of serial dot data in one main scan, while the line sync 58 is adapted for the main scan line synchronization in one frame (page). The other signals are the line gate 78 which indicates an effective time (number of dots) for one main scan, and the frame gate 80 which indicates an effective time (number of lines) for one frame (page). All the DMA operations or character generating operations are controlled by the four signals mentioned, so that serial dot data 74 is output from the character generator section 86 timed to the data clock 56.A timing control cirtcuit 88 generates a line reset signal 90 and a frame reset signal 92. The line reset signal 90 is equivalent to the line sync signal 58 and clears a dot counter for each main scan line to the initial condition.

The frame reset signal 92 occurs at the leading edge of the frame gate signal 80 to clear a line counter. The timing control circuit 88 switches over the data block 56 and line sync 58, line gate 78 and frame gate 80, and line reset 90 and frame reset 92 in accordance with the portrait/landscape printout operation.

The DMA counter 54 functions to generate addresses of the page memory 48 and font memory 50 and comprises a counter 94 responsive to the space (character) direction and a counter 96 responsive to the line direction.

During portrait printout, the space counter 94 is controlled by the data clock 56, line gate 78 and line reset 90 to serve as the main scan direction counter, while the line counter 96 is controlled by the line sync 58, frame gate 80 and frame reset 92 to serve as the subscan direction counter.

During landscape printout, all the signal lines are switched over so that the space counter 94 may turn out to be the subscan direction counter and the line counter 96, the main scan direction counter.

The space counter 94 generates a space address 98 associated with the page memory 48 and a chip select signal 100 associated with the font memory 50. The line counter 96 generates a line address 102 associated with the page memory 48 and a bit select signal 104 and a block select signal 106 associated with the font memory 50.The space address 98 and line address 102 are switched over from one to the other by a page memory address selector 108 depending upon the portrait/landscape operation, in conformity to the page memory address arrangement shown in Fig. 6b. The chip select signal 100 and bit select signal 104 are used to select either the five dots on the bit basis or eight dots on the chip basis in the submatrix of the one unit, one block shown in Fig. 4a; selecting each five dots in the event of the portrait printout and each eight dots in the event of the landscape printout.Of the data output from the page memory 48, a character select signal 11 0, a double print select signal 112, a unit select signal 114, a character font specify signal 116 and a double print font specify signal 11 8 are coupled to the font memory 50 as an address. A line control signal read out of the page memory 48 is fed to a line direction address control circuit 96 and an underline specify signal (UL, DUL) 122 to an underline synthesizer circuit 1 24. When commanded, the underline synthesizer circuit 124 adds underline dots to data read out of the font memory 50 at specified positions.The output data of the underline synthesizer 124 are fed in parallel to a shift register 126 and set therein by a shift register load signal 1 28. Timed to the data clock 56, the parallel data is converted into serial data and then fed from the shift register 126 to the plotter 34. The shift register load signal 128 is generated by the DMA counter control 54 and fed to the shift register 126 at a 5-dot period during portrait printout and at an 8-dot period during landscape printout. The reference numeral 130 designates a portrait/landscape command signal and 132, a double print command signal.

Referring to Fig. 9, the DMA counter control of Fig. 8 is shown in detailed block diagram. The space address counter 94 comprises a dot/line counter (dot counter for the portrait mode and line counter for the landscape mode) 1 34 and a space counter 136, each of which is a quinary counter. Therefore, the dot/line counter 1 34 delivers a carry out signal 1 38 in response to every fifth clock pulse. The carry out signal increments the space counter 1 36 which then delivers a space address signal 98. The carry out signal 138 also serves as the shift register load signal 128 in the case of the portrait operation mode.

The line direction address counter 96 comprises a line/dot counter 140, and a line/dot subcounter 142, (each being a line counter for the portrait mode and a dot counter for the landscape mode), a block counter 144 and a block sub counter 146, a line counter 148 and other control circuits.

The line/dot counter 140 and subcounter 142 normally function as octonary counters and respectively generate a carry out signal 1 50 and a carry out signal 1 52 each in response to every eight clock pulses. The carry out signals 1 50 and 1 50 increment their associated block counter 1 44 and subcounter 146, while serving as the shift register load signals for the landscape mode.

In detail, when the selector 1 54 has set the PLU or PLD flag, the carry out signal 1 52 from the subcounter 142 constitutes the shift register load signal 128 while, when none of the PLU and PLD flags are set, the carry out siganl 1 50 constitutes the same. It should be noted that each of the line/dot counter 140 and subcounter 142 operates as a hexanary counter.

The outputs of the line/dot counter 140 and block counter 144 are fed to a decoder 156 to generate line direction control timings. The timings required for the line direction control are provided by an end of line signal 158, a subcounter set signal 1 60 and a shift register load inhibit signal 1 62 to inhibit the output of pattern adapted to initialize the line/dot counter 140 and block counter 144, the subcounter set signal 1 60 to reinitialize the line/dot subcounter 142 and block subcounter 146, and the shift register load inhibit siganl 1 62 to inhibit the output of pattern data from the font memory 50 during scanning upper half of a line in response to a PLU request and during scanning lower half of a line in response to a PLD request.These three kinds of line direction control timing signals are selectively delivered through a selector 1 74 depending upon the requested line feed pitch, 1/8" or 1/6". That is, for the 1/8" line feed pitch, one line is defined by 38 lines or dots (38/300"=1/7.9") while, for the 1/6" line feed pitch, one line is defined by 50 lines or dots (50/300"=1/6"). Because one character in the font memory 50 comprises 48 dots along its height as described with reference to Fig. 3, the number of dots will be short by 50-48=2 in the case of the 1/6" line feed pitch.This does not matter at all for the portrait mode inasmuch as the sixth block in Fig. 3 is an unused area containing no dot data when read out, or for the landscape mode inasmuch as the line/dot counter 140 is forcibly reinitialized to cause no carry out signal 1 50 to appear. The 1/6" line feed may comprise 48 dots to set up 48/300"-1/6.25" so as to print out the figure in the approximate fashion.

The three different line direction control timing signals will be described hereinafter.

(i) 1/8" Line Feed Request The end of line signal 1 58 appears in response to every 38 lines/dots to reinitialize the line/dot counter 140 and block counter 144. During the portrait operation mode, both the counters 140 and 1 44 continuously count the leftmost pattern bit numbers in Fig. 3 from the top to the bottom and then cleared to "0" by an end of line signal 1 58 as soon as they count 38 bits (up to the bit 2 of the block 4). During the landscape operation mode, the range "0" to "38" shown in the right most part of Fig. 3 will be counted and, therefore, the line/dot counter 1 40 is present to "2" so that a set of 38 dots may be output four times by each eight dots (one byte) and a carry out signal 150 may be generated by the remaining six dots.The subcounter set signal 1 60 is adapted to generate a half a line shifted address and is deviated 38/2=1 9 lines/dots. The function of this signal 1 60 is equivalent to that of the signal 158, i.e., appearing when the bit 6 of the block 2 in the leftmost part of Fig. 3 is started (vertically) and when 1 9 dots have been counted upwardly from "0" in the rightmost part of Fig. 3 (horizontally).

The shift register load inhibit signal 1 62 inhibits data output for half a line and indicates a scan time for the lines/dots Nos. 0-1 8. A load signal inhibit circuit 164 inhibits the shift register load signal 128 for the period of lines/dots Nos.

0--18 in response to a PLU request and for the period of lines/dots Nos. 1 9-38 in response to a PLD request, thereby causing blank printing in either case.

(ii) 1/6" line feed The end of line signal 1 58 appears for every 50 lines/dots to initialize or clear the line/dot counter 140 and block counter 144 to "O". The subcounter set signal 1 60 is generated in response to half a line shifted value and, therefore, it is a signal shifted 50/2=25 lines/dots. That is, the signal 1 60 appears at the start point (vertical direction) of the bit 6 of the left-hand block 4 in Fig. 3, and at the start of a count (horizontal direction) of the 24th dot from the right-hand bottom. The function of the signal 1 60 is equivalent to that of the end of line signal 1 58. The shift register load inhibit signal 162 indicates a scan time for the line/dot Nos. 0-24.

The load signal inhibit circuit 1 64 inhibits the load signal 128 to effect blank printing for the period of the line/dot Nos. 0-24 at the space address where a PLU request is present, and for the period of the line/dot Nos. 25-49 at the space address where a PLD request is present.

As seen from the above, the line/dot subcounter 142 and block subcounter 146 shown in Fig. 9 indicate values which are shifted half a line relative to the line/dot counter 140 and block counter 144, respectively. The output of the line/dot counter 140 allows the bit select signal 104 for the font memory 50 to be delivered via a selector 1 66 only during the portrait operation mode.The output of the block counter 144, on the other hand, is adapted to deliver the block select signal 106 for the font memory 50 via a selector 1 68. Here, if PLU or PLD is requested, the outputs of the line/dot counter 140 and block counter 1 44 are switched over to those of the line/dot subcounter 142 and block subcounter 1 46 by the selectors 1 66 and 1 68, respectively.

Before reaching the font memory 50, the block select signal 106 is input into an adder 1 70 so that, in response to a 1/8" line feed request (while the LF flag is supplied from the CPU), "1" is added thereto to forcibly increment the block number.

This means forced skipping of the block No. O of the dot matrix shown in Fig. 3. That is, out of the 48 dots along the height of a character, the upper eight are removed to reduce the number of dots to 40 and the lower two are also removed to make it 38, so that a 38-dot character matrix is printed out. It will be noted that characters designed over the entire height appear partly omitted when printed out at the 1/8" line feed, that is, the 1/8" line feed is applicable only to those characters which are designed to be printed out without any omission against such a line feed pitch. The reference numeral 172 in Fig. 9 designates a portrait/landscape specify signal.

Referring to Fig. 1 Oa, there is shown the font memory control of Fig. 8 in block diagram.

In Fig. Oa, four font memory banks 178,180, 1 82 and 184 are employed each of which comprises five ROMs (C1--C5) each having a capacity of 64 kilobits (8-bit parallel output). The five ROMs provide one font. Characters may be stored 128 per font memory bank. Whatever the type of the memory may be, the same construction may be employed to realize the font memory 50. The 1/10" characters, 1/12" characters,1/15" characters and P.S. characters may have their dot patterns stored in desired ones of the font memory banks 178, 180, 182 and 184.

The control shown in Fig. 1 Oa is assumed to be capable of assessing the same font memory both in the portrait direction and in the landscape direction. Also, the control is capable of simultaneously reading out dot patterns out of any desired two banks and combining them through wired-OR of a bus 1 86 to effect overlaid printout. Selectors 188, 190, 192 and 194 are adapted to select either the character select signal 110 or the overlay character select signal 11 2. Of the four selected signals, one designated by a decoder 1 96 is delivered as the character select signal 110, while the other three are designated by a decoder 198 as an overlay character select signal 11 2 only when the overlay command 132 exists.Thus, the decoder 1 98 specifies either one of the banks 1 78-184 as an overlay print font in response to an overlay command 132. So long as the overlay command 1 32 is absent, all the outputs of the decoder 1 98 are invalid so that no characters will be printed out in the overlay mode. The overlay command 132, like the portrait/landscape command 130, is assumed to be set in a register (not shown) from the CPU 42 before the start of DMA.

The outputs of the decoders 196 and 198 have one-to-one correspondence and processed by an OR gate to become a signal which validates the font banks 1 78-1 84. Because the pattern loaded in each of the font banks 178-184 is constituted by five chips (C 1--C5), the validating signal is coupled in parallel to each bank so that the outputs of the five chips become valid all at the same time. Therefore, in response to an overlay command, the pattern data stored in any desired two of the banks are passed through the wired-OR of a data output bus 186, thus appearing as a combined output. That is, because each of the chips (C1--C5) comprises eight bits and the five chips are accessed at the same time, each font bank delivers 40 bits of data.In the absence of the overlay command one of the banks will be specified to deliver 40 bits of data.

As shown in Fig. 1 Ob, the font memory allocates bits 0--2 to a bit/chip select address (138), bits 16 and 17 to a font select address (125) and bits 3-15 to an in-bank address. The in-bank address comprises a unit select address constituted by the lower three bits, a block select address constituted by the intermediate three bits, and a character select address constituted by the upper seven bits. Any one of the banks is selected by a bit/chip select signal 202 output from a bit/chip selector 200 and font select signal 11 6 or 11 8, delivering one character of pattern data stored in its in-bank address.

The 40-bit data read out of the bank is coupled to a bit select circuit 204 during the portrait operation mode and to a chip select circuit 206 during the landscape operation mode. The bit select circuit 204 and chip select circuit 206 are controlled by the portrait/landscape command signal 130 to function one at a time. The 40-bit pattern data appearing on the output bus 1 86 are all the data contained in a submatrix shown in Fig.

3 which is defined by one unit and one block (5x8 dots). During the portrait mode, the bits 7-0 correspond to eight main scan lines and five bits are selected and delivered for each main scan line. During the landscape mode, the chips 5-0 correspond to five main scan lines and eight bits are selected and delivered for each main scan line. Eventually, the dot data are delivered at the period of five dots for the portrait direction and at the period of eight dots for the landscape direction. The underline synthesizer circuit 124 shown in Fig. 8 decodes the bit/chip select signal 202 and block select signal 106 and, in response to an underline request, forcibly synthesizes an underline in a predetermined character matrix position.

Another embodiment of the present invention will be described with reference to Figs. 11-14 which is directed to improving the quality of overlaid characters attainable with the embodiment described above.

Shown in Fig. 11 is an example of dot patterns which individually comprise a standard 40x32 dot matrix stored in a pattern memory (ROM). The dot pattern shown is the umlaut as a representative of diacritics which require overlaid printing.

Further, shown in Figs. 1 2a-1 2c are examples of proportional space alphabets stored in a pattern memory and including capital and small letters. The character "A" comprises a 40x28 dot matrix, the character "a" a 40x20 dot matrix, the character "0" a 40x24 dot matrix, the character "o" a 40x20 dot matrix, the character "U" a 40x24 dot matrix, and the character "u" a 40x20 dot matrix. In case where the dot pattern data read out of the pattern memory is fed to a dot printer of the type in which the head is fed at a predetermined speed in the subscan direction, it is necessary that each string of 40 dots be sequentially delivered for each main scan line while the pattern memory is accessed byte by byte in the main scan direction. In such a situation, each character width is determined by the number of subscan lines.

Basically, the present invention contemplates to provide dot pattern data of an overlaid character by obtaining OR of dot pattern data of a mark and that of a character with which the mark is to be combined, each being read out of a pattern memory. However, should the data be processed such that the dot pattern of a character whose width differs from the others as shown in Fig. 1 2a is combined with a dot pattern of a diacritic having a standard width as shown in Fig.

11, the diacritic would become laterally displaced from the character or, in the case of a small letter, it would be positioned so high above the character bringing the entire pattern out of proportion.

In light of this, the second embodiment is designed to achieve well balanced overlaid dot pattern data by reading dot pattern data of a mark out of a specific area of a standard dot matrix which matches with the width of a character or the capital or small letter, and providing OR of the dot pattern of the mark read out of the variable area and the dot pattern of a character. In detail, as shown in Fig. 1 2b, the character "0" is provided with the dot pattern of the diacritic (3) which is obtained by reading data out of the 1 st to 5th bytes in the main scan direction on each of the 3rd to 30th lines in the subscan direction shown in Fig. 11.Likewise, data in the second byte and onward on the 7th to 26th lines are read out for the character "o", data in the first byte and onward on the 5th to 28th lines for the character "U", and data in the second byte and onward on the 7th to 26th lines for the character "u". The resulting dot patterns of the diacritic are shown in (4), (5) and (6) of Fig. 12b. In Fig. 12b, (1) and (2) individually indicate spaces (blanks). Combining the characters shown in Fig. 1 2a with the diacritic in different dimensions and positions shown in Fig. 1 2b is effective to realize well balanced overlaid characters for all the characters having different widths as well as capital and small letters.

It will be seen from the above that in accordance with this embodiment all the characters having different widths, capital and small letters can be combined with marks which are fairly proportioned therewith in one-to-one correspondence. This is attainable merely by storing a standard character pattern of a mark to be overlaid on a character, i.e., without storing a plurality of character patterns in a pattern memory. The result is the efficient use of the memory.

Referring to Fig.13, there is shown a practical example of the construction for applying the embodiment described above to a dot printer. A character code signal is coupled from the outside to a printer control system which is adapted to control a printer 210 and comprise of an interface 212, a CPU 214, a program memory 216, a work memory 218 and a control register 220. A character data generation device 222 responds to a command from the CPU 214 by supplying the printer 210 with the data of a character pattern (inclusive of a mark to be overlaid) in the form of a dot matrix. Thus, the construction shown in Fig.

1 3 is basically similar to the construction shown in Fig. 2. The printer 210 is capable of printing out a predetermined maximum number of characters per line. A buffer memory section is included in the work memory 218 in order to accumulate character code signals.

In operation, in response to a character code, the interface 21 2 delivers an interrupt signal INT1 to the CPU 214 so that the CPU 214 accumulates the character code signal in the buffer memory section of the work memory 218. As one line of character codes signals are fully stored in the buffer memory, the CPU 214 supplies a print command to the printer 210 via the control register 220 while, at the same time, triggering the character data generator 222. The character data generator 222 generates dot pattern dots for each character in the form of a dot matrix and serially delivers the data timed to the clock of the printer 210. As soon as one character of data is fed out, the character generator 222 applies an interrupt signal INT2 to the CPU 214 to request for the next dot pattern data.The program memory 21 6 has therein a head address table for the stored dot pattern data corresponding to character codes and a conversion table for converting character widths of the dot patterns.

Therefore, the data set in the character data generator 222 from the buffer memory are the converted head address and character width data.

The character data generator 222 is shown in detail in Fig. 14. A first register 226 has a register section 228 for storing a head address of a pattern memory 224 which stores the dot pattern data corresponding to the character code signal in dot matrix. A second register 230 has a register section 232 for storing character width data. A third register 234 has a register section 236 for storing the head address of an overlay mark which is determined by the CPU 214 to match with a specific character width. The other register sections 238, 240 and 242 of the first to third registers 226-234 are allocated to the head address, character width data and overlay mark head address associated with the next character, respectively.The first to third registers 226-234 are the output registers of the CPU 214 and respectively set by commands IOWR1-1, IOWR1 - 2, lOWR2-1, IOWR2-2, lOWR3-1 and IOWR3-2.

Provision of two register sections in each of the first to third registers 226-234 is for the following reason. Where the printer 210 comprises a charge control type ink jet printer in which a print head is driven continuously in a predetermined direction, the dot pattern data fed to the printer 210 has to be continuous serial data. However, because the procedure up to the entry of the head address of a character, a print width data and the h'ead address of an overlay mark in the first to third registers 226-234 is programmed in advance, the time period necessary for the entry is varied in accordance with the kind of a character, print conditions, etc. Thus, the two register sections in each of the first to third registers serve to absorb the resulting discontinuity.

Timed to the clock fed from the printer 210, the dot pattern data (8 bits) read out of the pattern memory 224 in parallel in the main scan direction of the dot matrix are converted into serial data and fed from the shift register 244 to the printer 210. Upon completion of the data delivery from the shift register 244, a dot counter 246 adapted to count the clock (octanary counter) generates a carry signal in response to which the next parallel data are loaded in the shift register 244 and, at the same time, an address counter 248 is incremented to update the address. A comparator 250 compares the content of the access counter 248 with the print width loaded in the second register 230 and generates a coincidence output when one character of data has been delivered from the shift register 244.

The coincidence output serves as the interrupt signal INT2 which informs the CPU 214 of the end of one character of data output. The coincidence output also functions to reset the address counter 248 and inverts a flip-flop 252 for register switchover. Each of the first to third registers 226-234 has a 3-state output structure, while wired-OR connection is employed between the registers sections 228 and 238, register sections 232 and 240 and register sections 236 and 242. Hence, one of the paired register sections will be selected in response to the Q or Q output of the flip-flop 252. The content of the address counter 248 is coupled to an adder 254 to be thereby added to a head address output from the first register 226.Every time the address counter 248 is incremented, the head address for accessing the pattern memory 224 is updated a byte at a time in the order of dot matrix output.

Likewise, the head address of an overlay mark will be updated by an adder 256. A dot counter 258 delivers a carry signal for driving a monostable multivibrator 260 which serves as a timer which remains turned on while the pattern memory 224 is being accessed. While the timer remains turned on, its Q output selects a B output of a selector 262 which is adapted for the selection of outputs of the adders 254 and 256. The 0 output also sets a dot register 264 which is connected to the output of the pattern memory 224. In this construction, the pattern memory 224 is accessed via the B input of the selector 262 so that the dot pattern data of an overlay mark is read thereoutof and stored in the dot register 264. As the multivibrator 260 is turned off, the B input of the selector 262 is switched over to an A input whereby the head address from the adder 254 accesses the pattern memory 224. This provides OR of the dot pattern data of the character thus read out and the dot pattern data of the overlay mark stored in the dot register 264.

The OR is fed to the shift register 244 which then delivers serial data associated with the dot pattern of the overlay character to the printer 120.

In short, the character data generator is constructed such that the single pattern memory 224 stores both the dot pattern data of characters and the dot pattern data of marks to be overlaid.

A character and a mark are accessed one after the other. The dot pattern read out by the first access is held a moment in a register and, then, its OR with dot pattern data read out by the second access is obtained. Thus, a single pattern memory suffices for the overlay printout operation in contrast to the conventional pattern memories which are accessed independently of each other.

In summary, it will be seen that the present invention permits the line to be fed at desired one of various pitches and even allows characters of different pitches to be printed out together on the same line in the same page, each with a simple construction and arrangement. Also, the present invention is capable of combining various dot patterns to reproduce overlaid characters without any increase in the capacity of storage means.

The composite or overlaid dot pattern is high quality due to its desirable proportion.

Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof. The circuit arrangements shown and described are not limitative but may be replaced by others as long as their functions are equivalent. The numerical values such as the line feed pitch and the number of dots constituting a matrix may be other than those shown and described.

Claims (8)

Claims

1. A dot pattern print control method which accumulates print data transferred from a host machine and feeds dot pattern data corresponding to the accumulated print data from a storage means, thereby printing out a dot pattern based on the dot pattern data, comprising the steps of: (a) specifying a print position of the dot pattern at a desired pitch in response to the print data; and (b) delivering from the storage means a dot pattern which corresponds to the pitch of the specified print position.

2. A dot pattern print control method which accumulates print data transferred from a host machine and feeds dot pattern data corresponding to the accumulated print data from a storage means, thereby printing out a dot pattern based on the dot pattern data, comprising the steps of: (a) delivering from the storage means at least one group of dot pattern data simultaneously in response to the print data; (b) combining the dot pattern data when at least two groups of dot pattern data are output from the storage means; and (c) printing out a dot pattern in response to the composite dot pattern data.

3. A dot pattern print control method which accumulates print data transferred from a host machine and feeds dot pattern data corresponding to the accumulated print data from a storage means, thereby printing out a dot pattern based on the dot pattern data, comprising the steps of: (a) delivering first dot pattern data in response to print data; (b) delivering, when designated by the print data, a predetermined portion of second dot pattern data in correspondance with the first dot pattern data; (c) combining the dot pattern data output at steps (a) and (b); and (d) printing out a dot pattern in response to the composite dot pattern data.

4. A dot pattern print control apparatus having an accumulator means for accumulating print data transferred from a host machine and a storage means for storing dot pattern data, wherein dot pattern data corresponding to the print data accumulated in the accumulator is delivered from the storage means and a dot pattern is printed out in response to the dot pattern data, comprising: (a) a means for specifying a print position of the dot pattern at a desired pitch in response to the print data; and (b) a storage means for delivering a dot pattern corresponding to the pitch of the specified print position.

5. A dot pattern print control apparatus having an accumulator means for accumulating print data transferred from a host machine and a storage means for storing dot pattern data, wherin dot pattern data corresponding to the print data accumulated in the accumulator is delivered from the storage means and a dot pattern is printed out in response to the dot pattern data, comprising: (a) a storage means for delivering at least one group of dot pattern data simultaneously in response to the print data; (b) combining dot pattern data where at least two groups of dot pattern data are output from said storage means; and (c) a means for printing out a dot pattern in response to the composite dot pattern data.

6. A dot pattern print control apparatus having an accumulator means for accumulating print data transferred from a host machine and a storage means for storing dot pattern data, wherein dot pattern data corresponding to the print data accumulated in the accumulator is delivered from the storage means and a dot pattern is printed out in response to the dot pattern data, comprising: (a) a storage means for delivering a first dot pattern in response to the print data; (b) a storage means for delivering, when designated by the print data, a predetermined portion of second dot pattern data in correspondance with the first dot pattern data; and (c) a means for combining dot pattern data output as steps (a) and (b) in response to the composite dot pattern data; and (d) a means for printing out a dot pattern in response to the composite dot pattern data.

7. A dot pattern print control method substantially as herein described with reference to Figures 2 to 14 of the accompanying drawings.

8. A dot pattern print control apparatus substantially as herein described with reference to Figures 2 to 10 or Figure 14 of the accompanying drawings.