JP4010387B2 - Display drive control circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display drive control circuit for switching a character's full-width / vertical double-angle display on a character-type dot matrix display.
[0002]
[Prior art]
As a first method for displaying a character in double-wide angle, conventionally, for example, in the case of the letter “B”, in addition to the full-width font that becomes the display 51 shown in FIG. As shown in the figure, the upper half of the vertical double-width font is created in advance as one full-width font that becomes the display 52, and the lower half is created in advance as another full-width font that becomes the display 53, and these are created as LSI full-width font ROM of the display drive control circuit There is a method to store in. In FIG. 4, □ indicates non-lighting and ■ indicates lighting.
[0003]
In this method, when the double-width display is performed, the full-width font in the upper half of the double-width and the full-width font in the lower half of the double-width are displayed in combination in the vertical direction as shown in FIG. .
[0004]
As a second method, a special font ROM for vertical double angle is prepared separately from the full-width font ROM and mounted on the LSI of the display drive control circuit so as to read it out. The double-byte font ROM capacity is twice as large as the full-width font ROM.
[0005]
Further, as a third method, as disclosed in Japanese Patent Application Laid-Open No. 9-244582, when full-width font is read and segment data of a specific line of the font is sent to the display device in the case of double vertical display. In addition, there is a display that performs vertical double-angle display by selecting two adjacent common lines of the display.
[0006]
[Problems to be solved by the invention]
However, in the first method, when switching from full-width display to double-height display, as shown in FIG. 5, it is necessary to erase the full-width display and rewrite it using double-high-size font data. This is the same when switching from double-angle display to full-width display, and the display control program is complicated. In FIG. 5, 60 is a display.
[0007]
Further, in addition to one full-width character for each character, it is necessary to store font data for two characters for a vertical double angle, that is, a total of three characters in the font ROM. Since these full-width and double-width fonts are mixed in the same ROM, it is possible to display double-width characters simply by changing the font ROM for conventional circuits. In this case, the type of font to be used There was a problem that became 1/3.
[0008]
In the second method, there is no problem that the type of font that can be used is reduced to 1/3 as in the first method because a special double-size font ROM is provided. Since the amount of data becomes three times, when these are mounted on an LSI, the area becomes nearly three times that of an LSI having a full-width font ROM, resulting in a high cost.
[0009]
In the third method, since the two common lines are driven at the same timing in the case of vertical double-angle display, the control circuit is complicated in addition to the problem that the contrast changes compared to the case of full-width display. There was a problem of becoming.
[0010]
The present invention has been made in view of the above points, and an object thereof is to provide a display drive control circuit that solves the above-described problems.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention sends data for sequentially specifying font lines corresponding to data for sequentially specifying common lines of a dot matrix display to a font memory, and the font of the font selected by the display memory is sent. Ri send data for a particular line segment driver, if full-size display of changing data specifying the font line every time data for specifying the common line changes, double height display the common line when the Full-width / double-width characters that select twice the character code for one line to be displayed twice in the display memory by changing the data that designates the font line once every time the data designating the character changes twice in the display drive control circuit provided with a switching means, the data specifying the common line LSB, 2SB, 3SB When the MSB has 4 bits and the data for specifying the font line in the font memory has 3 bits LSB ′, 2SB ′, and MSB ′, when the full-width / vertical double-angle switching means is for full-width display, the LSB '= LSB, 2SB' = 2SB, MSB '= 3SB, and all character codes of the display memory are repeatedly selected, and for vertical double angle display, LSB' = 2SB, 2SB '= 3SB, MSB' = In addition to the MSB, the character code for one line of the display memory is repeatedly selected twice .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram showing a configuration of a display drive control circuit 10 according to an embodiment of the present invention. Reference numeral 11 denotes a display digit counter, from which a line pulse indicating one line is sent to the common line counter 12 and digit data (4 bits) indicating a display digit is sent to the display RAM 13. The common line counter 12 counts up each time a line pulse arrives from the display digit counter 11 and sends data (4 bits) to the common driver 14 and full-width / vertical double-angle switching circuit 15. Character codes (8 bits) such as characters and symbols to be displayed are written in advance in the display RAM 13 for 32 characters, and a 16-digit character code corresponding to the digit data coming from the display digit counter 11 is selected. The first or second row is selected by the MSB of the line counter 12. Reference numeral 16 denotes a font ROM that stores a plurality of types of fonts of 8 vertical dots and 5 horizontal dots. A font ROM is selected corresponding to the character code sent from the display RAM 13, and line data (segment data) of the font is selected. Is read as 3-bit data from the full-width / vertical double-angle switching circuit 15 and sent to the segment driver 17. The segment driver 17 latches the segment data of the same line for 16 characters and sends it to the segment signal line of the liquid crystal display 20.
[0014]
Reference numeral 20 denotes a dot matrix type liquid crystal display device which can display 16 characters in the horizontal direction and 2 characters in the vertical direction, that is, 16 characters per line for two lines. If one character is 8 dots long and 5 dots wide, the common driver 14 drives 16 common signal lines.
[0015]
When the switch 15a is switched to the side indicated by the solid line in FIG. 1, the full-width / vertical-double-angle switching circuit 15 described above has 4-bit data LSB to MSB (data for driving the common driver 14 and the data for driving the common driver 14). The lower 3 bits LSB to 3SB of the same) are sent to the font ROM 16 as LSB 'to MSB', and a specific font line among the 8 font lines of the specific font specified by the display RAM 13 in the font ROM 16 is sent. specify. At this time, the 4-bit data from the display digit counter 11 and the MSB of the common line counter 12 are sent to the display RAM 13 as they are, and a character code of a specific digit among the 32 character codes is selected. In other words, when the MSB of the common line counter 12 is “0”, the character codes from the first digit to the 16th digit (first row), and when the MSB is “1”, the character code of the 17th to 32nd digits (second row). Is selected.
[0016]
However, when the switch 15a is switched to the side indicated by the broken line, the upper 3 bits 2SB to MSB of the 4-bit data from the common line counter 12 are sent to the font ROM 16 as LSB 'to MSB'. The most significant bit MSB from the common line counter 12 is converted to “0” and sent to the display RAM 13. Therefore, the display RAM 13 repeatedly selects the first through sixteenth digits (first row) of the 32 character codes, and the seventeenth through thirty-second digits (second row) character codes are selected. Not selected.
[0017]
FIG. 2 is a diagram showing truth values of the 3-bit data LSB ′ to MSB ′ for selecting the font line of the font of the font ROM 16. When the switch 15a is on the solid line side, as shown in (a), the font lines 1 to 8 are sequentially selected when the common lines 1 to 8 are sequentially selected, and the font is also selected when the common lines 9 to 16 are sequentially selected. Lines 1-8 are selected sequentially. However, when the switch 15a is on the broken line side, as shown in FIG. 2B, when the common lines 1 to 16 are sequentially selected, the same font line is sequentially selected twice.
[0018]
When the switch 15a of the full-width / vertical double-angle switching circuit 15 is switched to the solid line side, the font ROM 16 selects the first font line of the 16 fonts sequentially designated by the display RAM 13, and the dot data. Is sent to the segment driver 17. At this time, since the first common line of the liquid crystal display 20 is selected by the common driver 14, a plurality of dots on the second line are selected by the segment driver 17 and driven simultaneously.
[0019]
Next, when the common line counter 12 advances by 1 count, the common driver 14 selects the second common line of the liquid crystal display 20, and the font ROM 16 selects the second font line of the 16 fonts and selects the segment. Since it is sent to the driver 17, a plurality of dots on the second common line are selected by the segment driver 17 and driven simultaneously.
[0020]
As described above, when the common driver 14 sequentially selects 16 common lines and the font ROM 16 sends segment signals for 16 font lines of a font of two lines (upper and lower two characters), one frame is sent. Is completed, and this is repeated.
[0021]
On the other hand, when the switch 15a of the full-width / vertical double-angle switching circuit 15 is switched to the broken line side, the MSB of the common line counter 12 remains “0”. Only the 16th digit character code is repeatedly selected. Further, the common driver 14 selects the common lines of the liquid crystal display 20 from the first to the 16th in order, and repeats the same. In the font ROM 16, the same font line is sequentially selected twice for one font, and this is repeated. Therefore, the liquid crystal display 20 displays the font character enlarged twice in the vertical direction.
[0022]
FIG. 3 is a flow when switching between full-width display and vertical double-angle display. As described above, in the present embodiment, two lines can be displayed in full-width, or the upper one line can be displayed in double vertical-width over two lines only by switching the switch 15a. Since no data rewriting is required, display control programs can be simplified.
[0023]
Further, since the common lines of the liquid crystal display 20 are sequentially selected and two lines are not selected at the same time, the contrast does not change.
[0024]
In addition, since a special font is not required as a font to be used, a conventional font ROM can be used as it is, and there is no cost problem such as an increase in chip size when the display drive control circuit is made into LSI.
[0025]
In the above description, the first to fourth bits are sent from the display digit counter 11 to the display RAM 13, and the fifth bit is sent from the MSB of the common line counter 12. The fifth bit is on the display digit counter 11 side. It may be created and sent via the switch 15a. Further, the case where two lines of characters or the like are displayed on the liquid crystal display 20 with 16 columns per line has been described as an example. However, the present invention is not limited to this, and the number of digits is arbitrary and the number of lines is 2 or more. The vertical double-angle display can be performed using any two lines. In this case, the data specifying the font line is changed every time the data specifying the common line is changed in full-width display, and the data specifying the common line is changed every time the data specifying the common line is changed twice in the vertical double-angle display. Data for designating the font line of the character for one line to be displayed in double angle may be changed once, and the character code for one line to be displayed in double vertical size may be selected twice in the display RAM. Further, the display is not limited to liquid crystal, and any dot matrix display can be applied.
[0026]
【The invention's effect】
As described above, according to the present invention, full-width display and double-high-angle display are performed without increasing the font, without the need to rewrite data when switching the display, and without simultaneously selecting two common lines. The advantage of being able to go up.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of a display drive control circuit according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of 4-bit data input to a font ROM from a full-width / vertical double-angle switching circuit.
FIG. 3 is a flowchart of full-width / vertical double-angle display switching according to the present embodiment.
FIG. 4 is an explanatory diagram of conventional vertical double-angle display.
FIG. 5 is a flowchart of conventional full-width / vertical double-angle display switching.
[Explanation of symbols]
10: display drive control circuit, 11: display digit counter, 12: common line counter, 13: display RAM, 14: common driver, 15: full-width / vertical double-angle switching circuit, 16: font ROM, 17: segment driver 20: liquid crystal display

Claims (1)

It sends data to sequentially specify the font line corresponding to the data to be sequentially designated the common line of the dot matrix display in the font memory, Ri send data for a particular line of the font that is selected by the display memory to a segment driver When full-width display is used, the data specifying the font line is changed every time the data specifying the common line is changed. When double-width display is used, the data specifying the common line is changed twice. In a display drive control circuit provided with full-width / longitudinal double-angle switching means for changing the data for designating the font line once and repeatedly selecting the character code for one line to be displayed in double-vertical double size in the display memory ,
When the data specifying the common line is 4 bits LSB, 2SB, 3SB and MSB, and the data specifying the font line of the font memory is 3 bits LSB ′, 2SB ′ and MSB ′, The vertical double angle switching means
For full-width display, LSB ′ = LSB, 2SB ′ = 2SB, MSB ′ = 3SB, and all character codes in the display memory are repeatedly selected,
In the case of double vertical display, LSB ′ = 2SB, 2SB ′ = 3SB, MSB ′ = MSB, and a character code for one line of the display memory is repeatedly selected twice. circuit.

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