JPH0572588B2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention is directed to a light emitting diode (hereinafter referred to as LED).
This invention relates to a time-division lighting device for a plurality of various display elements.

Conventional configuration and its problems Figure 1 shows an example of a conventional microcomputer-applied LED divided into four parts. 1 is the parent microcomputer, and 2 is the child that receives an external interrupt from the parent microcomputer 1. The microcontroller 3 is the output port COM1 to COM4 of the child microcontroller 2, where the time division drive waveform is generated, and the LED 4 is turned on only when the potential of the output port SEG 5 becomes "LOW". I can do it. Figure 2 shows each port of 3 from COM1 to
It shows the temporal change in the terminal potential appearing on COM4, and is shifted by 1/4 period. Here, t
is the first slot time, and 4t is one frame time composed of four slots. Then, in synchronization with the output waveform of each point COM1 to COM4 of 3,
A desired LED can be turned on by lowering the terminal potential of port SEG5 in FIG. 1 to "LOW". Figure 3 shows the flowchart, and at step 8, the common side drive output command causes COM1
Set the port "HIGH" to "HIGH" and set the SEG port "LOW" by the segment data output command at step 9.
Make it. 10 is a loop counter to buy time.

However, in the conventional method described above, when external interrupts occur frequently, the time required to process the external interrupts becomes large, and the time t for one slot in FIG. 2 increases significantly. In other words, if the time required for an external interrupt is τ seconds, and if an external interrupt occurs n times during t seconds, the time for one slot will be (t + nτ) seconds, which is different from the case where no external interrupt occurred. , there was a problem that the LED would flicker after nτ seconds.

OBJECT OF THE INVENTION The present invention solves the above conventional problems, and provides a lighting device that can prevent flickering of lighting even when an external interrupt occurs, especially when lighting is performed by software using a microcomputer. The purpose is to provide

Structure of the Invention In order to achieve the above objects, the present invention provides a lighting program that generates a time-division drive waveform, an external interrupt processing program, and a time required for one loop in the external interrupt processing program.
A microcontroller is equipped with a loop counter program to prevent flickering corresponding to the time required for one processing operation, and when an external interrupt occurs, the count number of the register in the loop counter is manipulated according to the number of external interrupts. The time-division driving time of the display element is kept constant.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below based on the drawings. In Figure 4, assuming that the register used in the loop counter is the R register, step 11 decrements the R register by 1, step 12 determines whether the R register is smaller than a certain number, and step 13 initializes the value of the R register. ing. The important point is that the loop where 11 and 12 meet is designed to be τ seconds. In Fig. 5, the time required for an external interrupt is τ seconds, and at 15, 1 is input from the R register.
Another important point is that

In other words, no matter how many times external interrupts occur, 1 is always subtracted from the R register at 15 in Figure 5 when returning, so the number of loops at 14 in Figure 4 is reduced by 1, and the difference is The pull becomes zero. To express it mathematically, if the number of external interrupts is n, then t + nτ - nτ = t,
The drive time of one common side will be kept at t seconds, and the drive time of the LED will be constant.
This eliminates unevenness in the drive waveform and prevents flickering.

Effects of the Invention The present invention, when lighting a display element such as an LED by time-division driving, can reduce the time delay caused by an external interrupt by manipulating a register in a loop counter. The time-division driving time is kept constant, as if no such phenomenon occurred, which helps prevent flickering of display elements such as LEDs and reduces eye fatigue.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a parent microcomputer and a child microcomputer that performs time-division driving, Fig. 2 is an example of waveforms during time-division driving, Fig. 3 is a general flowchart, and Fig. 4
5 show an embodiment of the present invention, FIG. 4 is a flowchart of a loop counter processing subroutine, and FIG. 5 is a flowchart of a main part of an external interrupt processing subroutine. 1...Parent microcomputer, 2...Child microcomputer, 3
...Common side output port, 4...LED, 5...
...Segment output port, 8...Common side drive output command, 9...Segment data output command,
10... Loop counter, 11... Instruction to subtract 1 from R register, 12... Determining whether R register is smaller than a certain number, 13... Initial setting of register, 14... 1 loop time τ seconds, 15 ……
Instruction to subtract 1 from R register.

Claims (1)

[Claims] 1. A lighting program that generates a time-division drive waveform, an external interrupt processing program, and a flicker prevention loop whose time required for one loop corresponds to the time required for one processing operation in the external interrupt processing program. - A lighting device that is equipped with a microcomputer that has a counter program, and that maintains the time-division driving time of the display element constant by manipulating the count number of the register in the loop counter according to the number of external interrupts when an external interrupt occurs. .