JP2003072158A - Control circuits and electronic equipment - Google Patents

Abstract

(57) [Summary] (Modified) [PROBLEMS] To provide a control circuit that shares a control circuit and a memory for different devices such as a liquid crystal display device and a thermal print head. A control circuit for simultaneously controlling a liquid crystal display device and a thermal print head, comprising a memory for storing image data for one screen of the liquid crystal display device, and reading out image data for one horizontal line from the memory. The thermal print head latches the data for one line in the time required for the thermal print head, and allocates the time required to read the image data for one screen from the memory to the print time for one line of the thermal print head. A thermal print head control circuit for controlling the head; and a liquid crystal display device control circuit for controlling to display one screen of the liquid crystal display device in a time required to read one screen of image data from the memory. Control circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for controlling a liquid crystal display device and a thermal print head at the same time. Further, the control circuit of the present invention is provided to a system including the liquid crystal display device and the thermal print head. It is related to the electronic device.

[0002]

2. Description of the Related Art In recent years, the integration of devices has advanced, and a system having both a display function of a display device and a printer function of printing and outputting the display contents has appeared. In particular, for portable applications, a liquid crystal display device is mainly used as a display device, and a printer equipped with a thermal print head is mainly used in terms of downsizing and low power consumption of the device.

FIG. 4 schematically shows a liquid crystal display device. The liquid crystal display device includes a scanning substrate having a plurality of scanning electrodes 5 formed in parallel on a transparent substrate and a signal substrate having a plurality of signal electrodes 6 formed in parallel on a transparent substrate with nematic liquid crystal interposed. Thus, the liquid crystal cell 1 is obtained in which the scanning electrodes and the signal electrodes are arranged so as to be opposed to each other, and the scanning electrodes and the signal electrodes are provided so as to be orthogonal to each other, and the pixels 4 are formed at each intersection in a matrix.

Each scan electrode is connected to a scan driver 3,
Each signal electrode is connected to the signal driver 2. In the case of a color liquid crystal display device, R is placed on each of the three adjacent pixels.
Color display is performed by disposing color filters of (red), G (green), and B (blue). A backlight is provided as a light source on the back surface of the liquid crystal display device.

The liquid crystal panel is driven by various display controls and selection of a pixel to be turned on by a display data signal, and a driving voltage is applied to the selected pixel to drive the liquid crystal to display a screen.

The scan driver 3 sequentially selects scan electrodes from above and applies a scan electrode selection voltage. Signal driver 2
In accordance with the selection of the scanning electrodes, the ON voltage is applied to the signal electrodes of the columns of pixels to be lit and the OFF voltage is applied to the signal electrodes of the columns of non-lit pixels.

To describe each driving signal, the voltage applied to the liquid crystal is AC driven in which the polarity is reversed at an appropriate cycle in order to prevent deterioration of the liquid crystal.

The FRM signal is sent to the scan driver and the first
This is a signal that gives the scanning electrode selection, that is, the scanning start timing.

The LOAD signal is a signal which is sent to the scan driver and the signal driver and gives a timing for synchronizing and outputting both drivers. CP is a clock for fetching the display data signal into the signal driver. DF is a timing signal that gives an AC cycle for AC driving the liquid crystal. D0 to Dn are display data signals, and usually a plurality of bits are sent in parallel to the signal driver, and 1 bit gives ON / OFF information of 1 pixel. In addition, the power supply circuit 7
Is a scan electrode selection voltage for driving the liquid crystal and ON
A voltage and an OFF voltage are generated and supplied to each driver.

Next, the outline of the thermal print head portion will be described with reference to FIG. A plurality of heating elements 11 whose heat generation is controlled by voltage application are arranged in a line on the insulating substrate.
Each heating element is connected to the output of the drive circuit. The print data DI is serially transferred to the drive circuit, one row of data is fetched by the internal shift register 10 by the clock pulse CLK synchronized with each data, and then one row of data is temporarily fetched by the row latch pulse LAT. Latch inside. The latched data controls the switching element 8 by the strobe signal STB and applies a voltage according to the data to the heating element 11.

A system in which the above liquid crystal display device and a thermal print head are combined is shown in the block diagram of FIG. Reference numeral 17 is a liquid crystal display device, 12 is a thermal print head, and a control circuit and a memory are provided for the liquid crystal display device 17 and the thermal print head 12, respectively.

For the liquid crystal display device 17, a liquid crystal display control circuit 14 and a display memory 13 for storing display image data.
And the central processing unit of the system sends the display image to this display memory for storage, and the liquid crystal display control circuit 1
Reference numeral 4 reads the display image data from the display memory 13, performs gradation processing, and then converts it into a data bus signal of D0 to 7,
LCD panel FRM, LOAD, CP, DISP, DF
Sent with the control signal of. At this time, the time for processing data for one screen must be suppressed to a maximum of about 14 milliseconds, and one line is usually required to have a processing speed of several tens of microseconds. If it deviates from this range, flicker or the like occurs, which affects the display quality.

On the other hand, the thermal print head 12 is also TP
An H control circuit 15 and an image memory 16 are provided. The central processing unit of the system sends print data for printing to the image memory, and the TPH control circuit 15 reads the image data from the image memory 16 and performs gradation processing. After that, the data signal DI
Is transferred to the thermal print head 12 together with LP, CLK, and STB control signals. At this time, the time required for processing one line is at least about 3 msec in view of print quality.

[0014]

As described above, the conventional system has a constitution in which different individual devices such as a liquid crystal display device and a thermal print head are arranged, and individual control circuits are structurally combined with each other. As a result, the time required for processing one screen and one line is greatly different, and it is difficult to share the control circuit and the memory. As a result, the size and shape of the entire system are increased and the cost is increased. .

The present invention has been completed in view of the above circumstances, and an object thereof is to provide a control circuit in which a control circuit and a memory are shared by different devices such as a liquid crystal display device and a thermal print head.

Another object of the present invention is to provide an electronic device of a display-printer integrated system which achieves downsizing and cost reduction for a system including a liquid crystal display device and a thermal print head.

[0017]

A control circuit of the present invention is a control circuit for controlling a liquid crystal display device and a thermal print head at the same time, and a memory for storing image data for one screen of the liquid crystal display device, and a memory for storing the image data. The time required to read the image data for one horizontal line from the memory by latching the data for one line in the thermal print head at the time required to read the image data for one horizontal line from the memory A thermal print head control circuit for controlling the thermal print head so as to allocate the printing time for one line and the time required to read the image data for one screen from the memory are displayed for one screen of the liquid crystal display device. And a liquid crystal display device control circuit for controlling in this manner.

The electronic equipment of the present invention is characterized in that the control circuit of the present invention is arranged in a system including a liquid crystal display device and a thermal print head.

According to the present invention, with the above configuration,
Regarding the processing time required for the liquid crystal display device and the thermal print head, the processing time is largely different from each other, and the prescribed memory required for each is shared.

To further describe this point, the liquid crystal display device and the thermal print head have conventionally required a memory capable of storing one screen of image information, and both devices read and read image information from the memory. According to the information, a liquid crystal display device converts into a display signal for display, and a thermal print head converts into a print signal for printing.

However, in the liquid crystal display device, it is necessary to constantly display one screen (read out image information) at high speed so as to prevent flicker, whereas the thermal print head is sufficient for heating for printing. It took a long time to print one screen (read image information) at a low speed.

In short, when the same image content is displayed on the liquid crystal display device and also printed on the thermal print head, the image information for one screen is the same, but the image information of different addresses is different. Was needed.

Therefore, in order to use a common memory, even if a single memory is used for both the liquid crystal display device and the thermal print head, data at different addresses cannot be read out at the same time. Even when the thermal print head tried to read the print data of the third line from the memory when displaying the display data of the second line, it could not be read by the single memory.

On the other hand, according to the present invention, with the above-mentioned configuration, even if there is a large difference in processing time, the control is performed so that the memory addresses of the required image data are the same. Is common.

[0025]

1 is a block diagram showing a configuration of an electronic device of the present invention, FIG. 2 shows an internal block of a control circuit of the present invention, and FIG. 3 is a timing chart of the control circuit of the present invention.

First, according to the electronic apparatus shown in FIG. 1, the control circuit 20 is connected to the oscillation circuit 18 and the memory 19, and the liquid crystal display device 2 is supplied with a signal from the control circuit 20.
1 and the thermal print head 22 are controlled.

According to the control circuit 20 shown in FIG. 2, the timing control circuit 23 sends a data read control signal from the memory 19 in synchronization with the clock from the oscillation circuit 18. The memory 19 transfers the held image data to the control circuit 20 based on the read control signal. The image data is composed of a plurality of bits of data having gradation information for each pixel. The read image data is converted by the frame gradation control circuit 24 into data suitable for controlling the gradation of the liquid crystal display device, and based on the timing signal from the timing control circuit 23, the liquid crystal control signal generation circuit. It is transferred to the liquid crystal display device 21 together with each liquid crystal control signal generated in 25. At the same time, the image data read from the memory 19 is converted into the print data DI of the thermal print head 22 by the THP gradation control circuit 26, and based on the timing signal from the timing control circuit 23, the TPH control signal generation circuit. It is transferred to the thermal print head 22 together with the thermal print head control signal generated at 27.

Next, the control circuit and control method of the present invention will be described in detail with reference to the timing chart shown in FIG.

In this example, a screen composed of 320 × 240 dots having 320 horizontal dots and 240 vertical lines will be described.

Image data for one screen of 320 × 240 is stored in the memory 19, and display information of several dots per address is stored in several bits. For example, if the display information is 256 colors for one dot per address,
Each address has a structure of 8 bits.

The control circuit 20 reads from the memory from the image data of 320 dots of the first line located at the top of the screen, and sequentially reads the second line, the third line, ..., The 240th line. Do line and read. In this example, since the screen configuration is 240 lines in the vertical direction, the second
By the time the 40 lines have been read, the data corresponding to exactly one screen has been read.

After that, the procedure returns to the reading of the first line, and the same operation is repeated.

The time required to read the data for one screen is set from the refresh time of the liquid crystal display device 21. That is, the liquid crystal display device 21 includes the memory 19
One screen of data is displayed in synchronization with the reading of one screen of data.

In order to maintain the display quality of the liquid crystal display device 21, it is necessary to operate one screen at 70 to 120 Hz and refresh it. In this example, 7
Assuming that it is operated at 0 Hz, 1 from the memory 19
If the readout time for the screen is t (f), then t (f) = 1/70
= 14.2 milliseconds, and if the time required to read one line is t (l), t (l) = 1 / (70 × 240)
= 59.5 milliseconds.

At this time, the thermal print head 22
Latches the data of the first line during a period in which the first one-screen data is read from the memory, that is, when the first-line data of the LCD first screen display period is read.

From the subsequent second line to the second 1 of the memory
The period until the reading of the first line of the LCD second screen display period, in which the data for the screen is read, is completed
It is assigned to the printing time of the image data of the line.

Further, when the data of the second line in the LCD second screen display period is read, the data of the second line is latched, and the second line of the LCD third screen display period is read from the subsequent third line. The period until completion is assigned to the printing time of the image data of the second line.

By repeating the same operation, the printing of the image data of the 240th line is completed by the 240th line of the LCD 241 screen display period. At this point, the thermal print head 22 completes the printing of one screen.

According to this operation, the time required for printing the thermal print head 22 is 1 per line, which is sufficient.
It can take 4.2 milliseconds.

[0040]

As described above, according to the control circuit of the present invention, the liquid crystal display device and the memory of the thermal print head can be used in common, whereby the system can be downsized and the cost can be reduced.

That is, the memory, which is an IC, is one of the expensive parts in the system circuit, and the external size and the number of terminals are not small at all. Therefore, by sharing the memory IC, the number of uses can be increased. The cost of IC is reduced by halving, and the PCB size required for IC mounting and wiring is also reduced (miniaturization).
As a result, downsizing and cost reduction of the system were achieved.

Further, according to the present invention, downsizing and cost reduction can be achieved even in an electronic device in which the control circuit of the present invention is arranged in a system including a liquid crystal display device and a thermal print head, and particularly the system itself. However, in a small product such as a portable application, the area and space occupied by the memory for the system become large, so that a sensible effect is achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a control device of the present invention.

FIG. 2 is a diagram showing an internal block of a control circuit of the present invention.

FIG. 3 is a diagram showing a timing of a control circuit of the present invention.

FIG. 4 is an explanatory diagram showing a structure of a liquid crystal display device.

FIG. 5 is an explanatory diagram showing a structure of a thermal print head unit.

FIG. 6 is a block diagram of a conventional system in which a liquid crystal display device and a thermal print head are combined.

[Explanation of symbols]

1. ． ． Liquid crystal cell 2. ． ． Signal driver 3. ． ． Scan driver 4. ． ． Pixel 5. ． ． Scanning electrode 6. ． ． Signal electrode 7. ． ． Power supply circuit 8. ． ． Switching element 9. ． ． Latch register 10. ． ． Shift register 11. ． ． Heating element 12, 22. ． ． Thermal print head 13. ． ． Display memory 14. ． ． Liquid crystal display control circuit 15. ． ． TPH control circuit 16. ． ． Image memory 17, 21. ． ． Liquid crystal display 18. ． ． Oscillator circuit 19. ． ． memory 20. ． ． Control circuit 23. ． ． Timing control circuit 24. ． ． Frame gradation control circuit 25. ． ． LCD control signal generation circuit 26. ． ． TPH gradation control circuit 27. ． ． TPH control signal generation circuit

Claims (2)

[Claims] 1. A control circuit for simultaneously controlling a liquid crystal display device and a thermal print head, the memory storing image data for one screen of the liquid crystal display device, and reading image data for one horizontal line from this memory. The thermal print head latches data for one line in the time required for printing, and the time required for reading one screen of image data from the memory is allocated to the thermal print head for one line of printing time. A thermal print head control circuit for controlling the print head and a liquid crystal display device control circuit for controlling to display one screen of the liquid crystal display device within a time required to read out one screen of image data from the memory. A control circuit provided. 2. An electronic device in which the control circuit according to claim 1 is arranged in a system including a liquid crystal display device and a thermal print head.