JPH0125982Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a display device using a light emitting diode (LED) or a fluorescent display tube (FLD).
In particular, the present invention relates to a display device with a large number of displays and a large number of display types.

(B) Prior art In general, in alphanumeric display or dot matrix display using LEDs or FLDs, one electrode is used as a digital electrode, and the other electrode common to each digital electrode is used as a segment electrode, and dynamic drive is used. Display devices are known. In such a display device, the display drive circuit is
In the case of a circuit that stores a large amount of display data, such as a microcomputer, the display drive circuit extracts the display data as needed and generates digital drive signals and segment drive signals based on the display data. was outputting. However, if a display that exceeds the display data storage capacity is required, the display data must be imported from outside. FIG. 1 shows a specific example.

In FIG. 1, each digit D ₁ ,
D _{2 ...} D _X are driven by digital drive _{signals DS 1 to DS} Driven by segment drive signals S ₁ to Sn.
The type of display displayed by this display body 1 is
If the capacity of the built-in memory of the microcomputer 2 is exceeded, the display data is stored in the external memory 3, and the display data is stored in the external memory 3 each time the display is performed.
I was importing display data from. However, the first
In the example shown in the figure, since display data is captured each time a display is performed, the number of displays that can be displayed simultaneously is increased depending on the transfer processing speed of the display data and other controls performed by the microcomputer 2. There is a drawback that it cannot be done.

(c) Purpose of the invention The present invention has been made in view of the above-mentioned points, and is a display device that has a large number of displays and a wide variety of display types, and has the capacity to perform processing other than display. It provides:

(d) Structure of the invention The invention provides a display body having a plurality of digital electrodes and a plurality of segment electrodes, a digital drive signal for dynamically driving the plurality of digital electrodes, and a segment drive signal for driving the plurality of segment electrodes. a main display control circuit that outputs a segment drive signal; and a sub display control circuit that receives a synchronization signal output from the main display control circuit in synchronization with the digital drive signal and outputs a segment drive signal based on the synchronization signal. The segment drive signal of the sub-display control circuit is applied to the display body through the same signal line as the segment drive signal of the main display control circuit.

(E) Embodiment FIG. 2 is a block diagram showing an embodiment of the present invention. The display body 4 is made of, for example, a fluorescent display tube,
Y digits from D ₁ to D _Y and each digit
It has n segments common to D ₁ to D _Y.
The main microcomputer 5, which is the main display control circuit, is a 4-bit one-chip microcomputer with built-in ROM and RAM, and dynamically controls each digit D ₁ to D _Y of the display 4 according to a program stored in the ROM. Digital scan signals DS ₁ to DS _Y for driving digital scan signals DS ₁ to DS _Y
At the same time, segment drive signals S ₁ -Sn corresponding to the digit scan signals DS ₁ -DS _Y are created using the display data stored in the RAM and applied to the segments of each digit D ₁ -D _Y. Also,
In addition to driving the display 4, the main microcomputer 5 performs arithmetic processing according to the program in the ROM, or outputs a control signal 6 to control an external device.

On the other hand, a sub-microcomputer 7 which is operated in parallel with the main microcomputer 5 is provided as a sub-display control circuit. The sub-microcomputer 7 is a 4-bit one-chip microcomputer, and transmits and receives data to and from the main microcomputer 5 via the data bus 8 according to a program stored in a built-in ROM. A synchronization signal 9 output from the main microcomputer 5 in synchronization with the output of the digital scan signals DS ₁ -DS _Y is input, and this synchronization signal 9 causes the digital scan signals DS ₁ -DS _Y to be output.
The segment drive signal is detected based on the display data stored in the built-in RAM.
Output S′ ₁ to S′n. The terminals to which the segment drive signals S' ₁ to S'n of the sub-microcomputer 7 are output are connected to the signal lines 10 to which the segment drive signals S ₁ to Sn of the main microcomputer 5 are output, ₁ to S'n are applied to the segments of the display 4 using the same signal line 10. Furthermore, the sub-microcomputer 7
Perform calculations according to the ROM program,
Alternatively, it also has a function of outputting a control signal 11 to control an external device.

Next, the operation of the embodiment shown in FIG. 2 will be explained using the waveform diagram in FIG. 3.

First, the RAM of main microcomputer 5
A large amount of data to be displayed is stored in the sub-microcomputer 7, and necessary data to be displayed by data transfer with the main microcomputer 5 has already been stored in the RAM of the sub-microcomputer 7. Then, the main microcomputer 5 outputs digital scan signals DS ₁ to _DSY according to a predetermined cycle. digital scan signal
As shown in FIG. 3, DS ₁ to DS _Y are signals in which pulses that are "H" for a predetermined period are sequentially output at predetermined intervals (planking period); The digit to which that signal is applied is selected. Therefore, when displaying display data stored in the RAM of the main microcomputer 5, the main microcomputer 5 sends digital scan signals DS ₁ to DS _Y as shown in a of FIG.
The data to be displayed stored in the RAM is retrieved without outputting the synchronization signal 9 that is synchronized with the data, and based on this data, the segment drive signals S ₁ to Sn are output at the same time as the digital scan signals DS ₁ to D _Y are output. . On the other hand, since the synchronizing signal 9 is not applied to the sub-microcomputer 7, the sub-microcomputer 7 does not perform a display operation and does not output the segment drive signals S' ₁ to S'n. That is,
The terminals of the sub-microcomputer 7 that output the segment drive signals S' ₁ to S'n are in a high impedance or floating state. Therefore, the display body 4 is driven by the segment drive signals S ₁ to Sn outputted from the main microcomputer 5 to perform display.

On the other hand, when displaying display data stored in the RAM of the sub-microcomputer 7, the third
As shown in figure b, the main microcomputer 5
outputs the synchronization signal 9 synchronized with the digital scan signals DS ₁ to D _Y , and outputs the segment drive signals S ₁ to
Sn does not output, and its output terminal is in a high impedance or floating state. The sub-microcomputer 7 to which the synchronization signal 9 is applied is
It counts the pulses of the synchronization signal 9, detects the rise and fall of the pulses, and recognizes the status of the digital scan signals _DS1 to _DSY output by the main microcomputer 5, that is, which digit is selected. Based on the display data stored in the RAM of the sub-microcomputer 7, segment drive signals S' ₁ to S'n are output.
Therefore, the display 4 displays a display based on the display data stored in the RAM of the sub-microcomputer 7.

Furthermore, as shown in FIG. 3c, the main microcomputer 5 outputs the synchronization signal 9 and also outputs segment signals S ₁ to Sn based on the display data stored in the RAM of the main microcomputer 5. It is also possible for the sub-microcomputer 7 to output segment drive signals S' ₁ to S'n based on display data stored in the RAM in accordance with the synchronization signal 9. In this case, the display shows segment drive signals S ₁ to Sn and segment drive signals
The display intended by the main _{microcomputer} 5 and the display intended by the sub microcomputer 7 overlap. In other words, multiple display is performed. In this multiplex display, one segment drive signal, for example, S ₁ to Sn, has a pulse duty that is smaller than that of the other segment drive signal, S' ₁ to S'n, for example, 1/2 or 1/4. By doing so, the brightness of the display displayed by the segment drive signals S ₁ to Sn is reduced, and it is possible to distinguish one display from the other display. For example, in the case of multiplexing graphic display and character display, the segment drive signal S ₁ ~
By displaying figures using Sn and displaying characters using segment drive signals S′ ₁ to S′n with large duty, high-brightness character display is multiplexed into low-brightness graphic display, and both The two displays can be identified together.

(f) Effects of the invention As described above, according to the invention, a display device with a large number of displays and many types of displays can be used with a display control circuit that has a limited storage capacity and operates at low speed. This is something that can be achieved. Furthermore, since the sub-display control circuit does not need to output a digital scan signal, it has the advantage of saving terminals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a timing diagram showing the operation of the embodiment shown in FIG. Explanation of main figure numbers, 4...Display body, 5...Main microcomputer, 7...Sub microcomputer, 8...Data bus, 9...Synchronization signal.

Claims (1)

[Scope of utility model registration request] a display body having a plurality of digit electrodes and a plurality of segment electrodes; a main display control circuit that outputs a digit drive signal for dynamically driving the plurality of digit electrodes and a segment drive signal for driving the plurality of segment electrodes; a sub-display control circuit that receives a synchronization signal output from the main display control circuit in synchronization with the digital drive signal, and outputs a segment drive signal synchronized with the digital drive signal based on the synchronization signal; A display device characterized in that the segment drive signal of the sub-display control circuit is applied to the display body via the same signal line as the segment drive signal of the main display control circuit.