FR2657988A1 - METHOD AND DEVICE FOR DISPLAYING ON DOT MATRIX SCREEN. - Google Patents

Abstract

The present invention relates to display on dot matrix screens and, in particular, on liquid crystal screens. Characters are stored in a character memory (2) in the form of points to be excited in a given area of a screen (1) in order to display these characters there. Depending on a display to be made on the screen (1) the addresses of the characters to be displayed are stored in a code memory (3, 3 ') in positions in one-to-one relationship with the positions to be given to these characters on the 'screen; the contents of the code memory make it possible to read the desired characters from the character memory and display them on the screen. Application, in particular, to screens of the thin-film transistor type.

Description

Method and display device

on a dot matrix screen.

  The present invention relates to the method and the electronic display device implementing a dot matrix screen. Among the dot matrix screens, the best known are the liquid crystal screens also called LCD screens (according to the initials of the English words Liquid Crystal Display), and in particular thin-film transistor or TFT type screens (according to the initials of the English words Thin film transistor) and generally nematic type helical nematic type TN (according to

  initials of the English words Twisted nematic).

  It is known to use a graphics microcomputer to read in a programmable read-only memory, called PROM (initials of the English words Programmable read-only memory), instructions for drawing information elements such as, for example, letters; these instructions are stored in a random access video memory called memory VRAM (initials of the English words Video random access memory) A memory VRAM includes a memory type RAM (according to the initials of the English words Random access memory), a register to parallel-series type offset and a scanning circuit which makes it possible to automatically and cyclically transfer the lines of the RAM memory into the shift register; the microcomputer writes and reads in the VRAM memory as in a simple RAM memory; the shift register of the VRAM memory provides, line by line, the information to be displayed on

the LCD screen.

  The microcomputer is responsible for generating the control signals from the VRAM memory or more generally from the two VRAM memories, one being in the working phase, that is to say that the memory information of the PROM memory plotting in the VRAM memory corresponding to the information to be displayed, the other memory VRAM being in the drawing phase, that is to say of transfer through its shift register traces it contains; the role of these two memories VRAM is permuted as soon as the plots necessary for the writing of all the new information to be displayed, were read by the memory in working phase, to generate the signals of synchronization and white of the signal video, to ensure the transfer of the trace information between the memories VRAM and the LCD screen by supplying the shift register of the memory VRAM phase drawing, a synchronization signal,

  to refresh the content of VRAM memories.

  In such a display device the graphic microcomputer, which wants to enter a given character at a given location of the LCD screen, takes in the PROM memory the drawing program of this character and calculates the points of the screen corresponding to this plot; this implements complex calculations: use of the Bresenham algorithm for the search of the points of the screen giving the closest effective plot of the theoretical plot defined by the PROM memory and arithmetic filtering which allows to keep only the points corresponding to the color, or colors

  desired for the character to display.

  Such a device has various disadvantages The need to use a graphics microcomputer and VRAM memories make this device is expensive The memories

  VRAM have a relatively high energy consumption.

  The calculations to be made make this device slow and it is even slower that the desired graphic quality is better; in addition, any calculation involving a rounding error, the need for numerous calculations to obtain a

  character often results in a distortion of the character.

  The present invention aims to avoid or, for the

  least, to reduce these disadvantages.

  This is achieved by storing, at known addresses, a set of characters preprogrammed for areas of given dimensions of the screen, in order to be able to retranscribe them on the screen according to the needs of a particular user.

information to display.

  According to the invention it is, in particular, proposed a display method on a dot-matrix screen, characterized in that it consists in: preprogramming, in a first memory, to known addresses, which are called character codes , the points to be excited of an elementary surface, of predetermined dimensions, of the screen, so that is displayed on the screen of the given characters to store line of characters by line of characters, in a second memory the character codes of the successive characters to be displayed on the screen to control the reading of the first memory by the second memory so as to display on the screen, the position of a character code in the second memory defining the position, called the primary position, from which the character corresponding to this character code must be displayed

on the screen.

  According to the invention there is also provided a dot matrix screen display device, characterized in that it comprises N first memories with positive integer N, in which are preprogrammed, at known addresses, which are called character codes , characters, that is to say the points to be excited of elementary surfaces of predetermined dimensions of the screen, so that is displayed on the screen these characters, at least N seconds memories respectively associated with the first N memories to contain character codes in positions having a one-to-one correspondence with points of the screen, and means for writing character codes in the N second memories, for reading the stored characters, corresponding to these character codes, in the first memories associated with the second memories o these codes are written and to display a character read with the points of the screen having a correspon one-to-one dance with the position of the character code that determined the reading. The present invention will be better understood and others

  characteristics will appear with the help of the description

  FIGS. 1 and 3 are a diagram of elements of a display device according to the invention, FIG. 2 a time base circuit, FIG. 4, a diagram for explaining a display device according to the invention, Figure 5, another display device according to the invention. In the various figures, the corresponding elements are designated by the same reference numerals. In the various electronic diagrams the precise synchronization devices, which are part of the current technology, have not been represented in order to make the drawings more

clear and simplify the presentation.

  FIG. 1 is a simplified diagram intended to facilitate the explanation of the operation of a device

display according to the invention.

  A liquid crystal display, 1, is supposed to display N = 4 lines of m = 4 characters each, CANE, DEFI, LIME and BAIL, these words being arranged one above the other; each character is arranged in a surface

  elementary equal to 1 / m N = 1/16 of the useful surface of the screen.

  This elementary surface is a rectangle that has x points

per line and y lines of points.

  A PROM memory, 2, called character memory, is preprogrammed by rectangular zones of x boxes per line and y lines; these memory zones therefore have a distribution of cells identical to the distribution of the points in an elementary surface of screen; that is to say that there is a one-to-one correspondence between the cells of a memory zone and the points of an elementary surface of the screen on which the character of the memory zone in question is displayed. The preprogramming of the memory 2 consists of a preprogramming of a character by memory zone, the binary elements 1 and O being arranged in the boxes whose positions respectively correspond to the points to be lit and to the points to be left extinct in an elementary surface of screen to obtain a Given character Thus, for example, the memory 2 contains, inter alia, the capital letters A to N of blue color; for ease of understanding it is not a 1 and O that have been represented in the memory areas of the memory 2 but the characters defined by these 1 and O Each memory area containing a character is identified by an address code constituted by the address of the first of its boxes that is read during a horizontal scan from left to right with moving up and down the reading line; so the letter A is at the address 0,0 and the letter L at the address

y + 5 x.

  A RAM, 3, called code memory, contains the addresses o are in the memory 2, the characters to be displayed on the screen; Thus, in order to display the word CANE in blue capital letters on the first line of characters on the screen 1, the first address line of the memory 3 comprises the following successive address codes: 0.2 × 0.0 2 y, x 0.4 x, similarly, to display the word DEFI in blue capital letters on the second line of characters on the screen, these are the character codes 0.3 x 0.4 x 0, 5 x and y , 2 x which are contained subsequently in the second address line of the memory 3 There is thus one-to-one correspondence between the lines of characters of the screen 1 and the address lines of the memory 3 and, in d other words, the position of a character code in the memory 3 defines the position, called the primary position, from which the character corresponding to this character code must be displayed on the screen 1. To display on the screen 1, the addresses

  from the same line of memory 3 are read y times in a row.

  When the lth address of a jth line of the memory 3, with i and j respectively between 1 and m and between 1 and n, including terminals, is read for the qth time, with q between 1 and y inclusive, the content of the qth line of the memory zone, of the memory 2, corresponding to the address in question, is read and the 1 and O thus read are respectively used to turn on and to leave off the x points of the qth line of the elementary surfaces of the screen 1 which is located at the intersection of the 1st column of elementary surfaces with the jth line of elementary surfaces. When the addresses of the same address line of the memory 3 have been read for the yth consecutive time, the reading of the memory 3 is continued to the next line which is also read y times and the reading continues thus to the last line of the memory 3, that is to say to the nth line, which is also read y times The reading of the address lines of the memory 3 then resumes from the first address line, to make a new display on the screen 1 and this new display is identical to the previous one as long as the contents of the memory 3 is not

not modified.

  Thus the device designed to perform the electronic display on a liquid crystal display, as it has been made, comprises a set of meters which is shown

in Figure 2.

  FIG. 2 shows a set of four counters Cx, Cm, Cy and Cn connected in series in this order to constitute a time base circuit. The first counter, Cx, is a modulo x counter which counts the display synchronization pulses. screen points; when the counter Cx goes through zero it provides a counting pulse to the counter Cm; in addition, each of these counting pulses constitutes a read pulse of a new address in the memory 3 and a transfer control of a parallel-series shift register, 7, which will be represented in FIG. the transfer to the screen 1 of the information stored in the memory 2 already described with reference to FIG. 1 The counter Cm is a modulo meter; when it goes through zero it provides a control pulse reading a line of characters from the memory 3 It was seen that each character line of the memory 3 was read y times in succession, that is why the impulses provided by the counter Cm are counted in the counter Cy which is a modulo counter y and which therefore provides, at each of its zero crossings, a next line reading pulse of characters in the memory 3 The set of addresses of the memory 3 is contained on N lines of addresses; the counter Cn, which is a modulo N counter fed by the following line reading pulses delivered by the counter Cy, thus provides, at each of its zero crossings, a pulse which signifies

  that a complete reading of the memory 3 has just been performed.

  The preliminary explanations given using FIGS. 1 and 2 will facilitate the understanding of FIG. 3, which is an overall diagram of a display device.

  electronic liquid crystal screen according to the invention.

  Figure 3 shows the screen 1, the character memory, 2, and the code memory, 3, of which it has already been

  question on the occasion of the description of Figure 3

  memory 3 operates in association with a memory 3 'identical to the memory 3 A multiplexing circuit, 6, symbolized by two switches controlled by a microcomputer 4, makes it possible to use one of the memories in the working phase while, the other is used in the drawing phase; this solution of the two memories of codes is little used; the device is fast, it is useful only if the microcomputer is slow or may be occupied with other tasks, in timeshare In the positions occupied in Figure 3, the circuit switches 6 it is the memory 3 which is in the drawing phase and the memory 3 which is in the working phase; that is to say that the memory 3 'is connected to the microcomputer 4 which, according to information to be displayed on the screen 1, provides it with the address codes corresponding to the next information to be displayed. plot, that is to say that a screen controller 5, controlled by the microcomputer 4, sweeps line by line the memory 3 to read the address codes according to the reading mode explained using the Figure 2: reading the address lines y times in a row. The role of the screen controller is therefore to read that of the two memories 3, 3 'which is in the drawing phase; for this the screen controller comprises the time base circuit according to Figure 2 The role of the screen controller is also to ensure the transfer to the screen 1, the information corresponding to these character codes read; this information is extracted from the character memory, 2, as explained with reference to FIG. 1 and the synchronization signals used for this transfer are provided by the set of counters according to FIG. 2; the transfer between the memory 2 and the screen 1 takes place via a parallel-serial register, 7, at x positions, that is to say at as many positions as there are points in a line of an elementary surface of the screen 1 and boxes per line in a memory area of the memory of

  characters, 2, o is programmed a character.

  The foregoing description has been implemented with

  the following values for the different parameters.

  x = y = 8 m = N = 60 which corresponds to a screen of 480 480 points and to code memories 3, 3 'capable of containing 60 60 address codes. In the above, the elementary surfaces of the screen all have the same dimensions: xy points It is also possible, as will be shown below, to make a display device where the elementary surfaces have different values according to the information to be displayed Figures 4 and 5 are diagrams for an example of

  realization of such a display device.

  Figure 4 shows three distinct Images EO, El, E 2 whose superposition is represented by a circle with a sign +, in which three arrows arrive and o starts an arrow; this superposition gives an image E which is the image to be obtained on a liquid crystal screen by using a display device of the type of that which has been described with reference to FIGS. 1, 2 and 3. The EO image corresponds to at the bottom of the image E, the image El corresponds to information of the image E which is little modified and the image E 2 corresponds to information of the image E which is often modified; in the images E1 and E2, broken lines indicate on the one hand the limits of the image E on the other hand the limits of the elementary surfaces occupied by each of the characters which constitute

the information in these Images.

  FIG. 5 represents a display device designed to display on a screen, 1, an image of the type of the image E of FIG. 4, from three signals which, taken separately, would respectively give on the screen, This is why the display device according to FIG. 5 differs from the one according to FIG. 3 by three circuits for storing the codes and storing the characters and summing them. , using an addition circuit 8,

  signals extracted from the circuits for storing characters.

  The display device according to FIG. 5 comprises a microcomputer 4 which defines in the surface of the screen 1 three distinct zones corresponding respectively to the zones occupied on the screen by the images E0, E1 and E2 of FIG. ; each of these areas is treated as is processed image

  in the display device according to FIG.

  That is to say, to obtain the image El on the screen 1, the device comprises, firstly, two code memories 31, 31 'and a multiplexing circuit 61 connected between the microcomputer 4 and a screen controller 5, in the same way as the circuits 3, 3 'and 6 in the device according to Fig. 3 and, on the other hand, a character memory 21 and a connected parallel-series shift register. between the screen controller 5 and an input of the addition circuit 8 whose output is connected to the video signal input of the screen 1 To obtain the image E 2 on the screen 1, the device of The display according to FIG. 5 comprises circuits 32, 32 ', 62, 22 and 72 respectively similar to the circuits 31, 31', 61, 21 and 71 and connected identically to obtain the image EO of FIG. 1, the display device according to FIG. 5 does not include two but only one code memory, 30, connected between the microcomputer 4 and the controller screen 5 because it is expected that the address codes contained in this memory will be very rarely changed; to obtain the EO image there is therefore no multiplexing circuit, on the other hand there is a character memory 20 and a parallel-series shift register 70 connected in the same way as the

circuits 21 and 71.

  It should be noted that the three-part processing of the image to be displayed on the screen 1 is intended to simplify the programming of the code memories; indeed when for example, only is to modify the content of information of the kind of those of part E 2 of image E of Figure 3, this avoids having to redo all the programming that concern the bottom of the image and the slightly modified part of the image, that is to say concerning information of the kind

  those of parts EO and E1 of image E of FIG.

  It should also be noted that, in the example according to FIGS. 4 and 5, the elementary surfaces on the screen are not the same depending on whether they serve to display the EO image, the El image or the image. image E 2; for the EO image the elementary surface is a square of dimensions a a, for the image E1 it is a rectangle of dimensions 1.5 3 a and for the image E 2 it is

a rectangle of dimensions 2 to 3 a.

  In the foregoing the information to display was limited to numbers, letters and a wallpaper, and, for simplicity, they were called characters; in a more general way these characters can consist of any drawing provided that the precision necessary for the representation of this drawing on the screen does not exceed the

  line accuracy that can be achieved with the screen.

  It should be noted that it is possible to represent animated characters, that is to say whose representation moves on the screen; a movement in the plane of the screen can always be reduced to the sum of a translation and a rotation, to represent an animated character it is necessary to modify the position of the character code in the code memory according to the translation to perform, and modify the value of the code to account for the rotation Moreover, when an animated character is constituted by identical patterns, regularly distributed over a circle, and when the density, on the screen, points used to represent this animated character is such that, in a rotation, a pattern takes the place of the next after a sequence of p images on the screen, it is sufficient to keep in memory of characters only p different characters corresponding to this sequence of p images Thus for represent the rotational movement of a watch dial made of a large stroke for each hour, just keep in memory of characters only thirty different characters in the mesu For a line to take the place of the next, there are thirty successive images, that is to say one image per degree of rotation It is also noticeable, on the occasion of the representation of a dial on a screen, that, if the dial includes, for example, numbers it is possible to rotate these numbers with the dial but keeping their orientation, that is to say that the top and bottom of the figure remain respectively turned up and down the screen to facilitate reading of these figures; for that the graduations of the screen will be treated like a first animated character and the numbers like other characters that

  will follow the movement of the graduations.

  The present invention is not limited to the examples described, it is thus that the elementary surfaces may not all be of the same size for the characters stored in the same character matrix, but it is then necessary that the screen controller in yours count for the number of successive times that a character must be read in a character memory. It is also possible, instead of scanning the screen line by line, to control the screen scan so as to display a character display after

character.

Claims (5)

  A display method on a screen (1) with a matrix of points, characterized in that it consists in: preprogramming, in a first memory (2; 20, 21, 22), to known addresses, which are called codes characters, the points to be excited of an elementary surface, of predetermined dimensions (x, y), of the screen, so that is displayed on the screen of the given characters to store line of characters by line of characters, in a second memory (3, 3 '; 30, 31, 31', 32, 32 '), the character codes of the successive characters to be displayed on the screen to control the reading of the first memory (2; 20, 21, 22); by the second memory (3, 3 '; 31, 31', 32, 32 ') so as to display on the screen (1), the position of a character code in the second memory defining the position, so-called primary position, from which the character corresponding to this character code must be displayed on the screen (1) 2 Selo display method n claim 1, characterized in that it consists in controlling the reading of the first memory (2; 20, 21, 22) by the second memory (3, 3 '; 30, 31, 31', 32, 32 ') as a function of a regular line-by-line scanning of the screen (1) to be stored in the second memory of the lines of characters whose characters all require the same number of lines, y, points on the screen to read y times in succession a line of the second memory whose characters require y lines of dots on the screen and, for this to write a character on the screen when the regular scan goes through the lines a to a + yl, at the intersection with the columns b to b + x-1, oa, b define the primary position, online and column, the character to write and ox is the number of columns of points of the elementary surface   occupied by the character to be written.   Process according to any one of the claims   precedents, characterized in that it consists in using   elementary surfaces having all the same dimensions.   4 Process according to any one of claims 1   and 2, characterized in that it consists of using surfaces   elementals of at least two different types of dimensions.   A dot-matrix display device (1), characterized in that it comprises N first memories (2; 20, 21, 22) with positive integer N, in which are preprogrammed, at known addresses, which are said character codes, characters, that is to say the points to excite elementary surfaces of predetermined dimensions (x, y) of the screen, so that is displayed on the screen these characters, at least N seconds memories (3, 3 '; 30, 31, 31', 32, 32 ') respectively associated with the first N memories to contain character codes in positions having a blunted correspondence with points of the screen (1), and means (4, 5) for writing character codes in the n second memories, for reading the stored characters, corresponding to these character codes, in the first memories associated with the second memories where these codes are written and for displaying a character read with the points of the ec ran with a one-to-one correspondence with the   position of the character code that determined the reading.   6 Device according to claim 5, characterized in that the second memories (3; 30, 31, 31 ', 32, 32') are of m number, with m integer greater than N and at most equal to 2 n, in that 2 (mn) of the second memories (3, 3 '; 31, 31', 32, 32 ') constitute pairs, the two second memories of a pair being coupled to a multiplexing circuit (6; 61, 62 two states, one of the memories of the pair being writable and the other read for one of the states and conversely for the other state.   7 Device according to claim 5, characterized in that the characters preprogrammed in one of the N first memories (2; 20, 21, 22) relate to elementary surfaces   having all the same dimensions.