JP2532463Y2 - Dynamic display circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dynamic display circuit which enables alarm display of, for example, a CPU (Central Processing Unit).

[Conventional technology]

Conventionally, in this type of dynamic display, a current several times higher than that in a normal stack display is applied to each digit of a plurality of arranged seven-segment LEDs (light emitting diodes), and the display is performed while switching the LED digits. It uses an afterimage on the retina of an image reflected by the human eye so that all digits are displayed.

These days, the CPU is used for switching this digit, and RTC (real
This processing is performed by an interrupt signal called time clock).

By the way, when the CPU is stopped, the current that is several times the normal
Because it flows statically to the ED, a mono-multi vibrator that selects the digit of each LED, turns off the display when the CPU does not start it, and operates in a fail-safe manner.

[Problems to be solved by the invention]

However, even if the CPU finds its own alarm, for example, a RAM (ram) error or a ROM (rom) total check error, another display is required to display this as an alarm [see, for example, -251446-Device for monitoring execution of program of invention name].

Here, an object of the present invention is to provide a dynamic display circuit capable of displaying an alarm on the same display unit in order to solve the above problems.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a multi-digit dynamic lighting display operation by a plurality of display elements based on a control signal from a CPU, and when the CPU is stopped, the multi-digit dynamic lighting display operation. In a dynamic display circuit for stopping the operation, a current output means for detecting an abnormal stop of the CPU and outputting a current, and a current output means connected to a display element of a specific digit of the plurality of digits, and outputting a current from the current output means. A current limiting resistor for limiting, when an abnormality occurs in the CPU, by statically lighting only the display element of the specific digit, an alarm display indicating that an abnormality has occurred in the CPU is performed. It is characterized by that.

[Action]

According to the above configuration, when an abnormality occurs in the CPU, the current from the current output means is supplied to only the display element at a specific digit via the current limiting resistor. That is, the display operation of the display element of the other digit is stopped, and only the display element of this specific digit is statically lit and an alarm is displayed. Therefore, with a simple circuit configuration in which only the current output means and the current limiting resistor are added, an alarm can be displayed when an abnormality occurs in the CPU.

〔Example〕

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

This embodiment is a mono-multi vibrator [HC423 re
Transistor array [TD62781AP / F] 8 from output terminal Q bar of triggerable monostable maltiviburator] 5
The connection to the 7-segment light-emitting element 40 of the specific digit, here LED0, through the resistor 9 and the resistor 9 therefrom is a signal circuit added to the circuit for normal dynamic / static lighting.

Here, the dynamic lighting operation will be described. The CPU (not shown) gives the data write signal / WRO6 and writes the display data of the N-th segment to the flip-flop 1. At this time, the signal of / WRO6 is cleared by clearing the latch circuit 7 which has selected the N-1 digit, and the display of the N-1 digit disappears.

Further, the CPU writes data for selecting the Nth digit to the latch circuit 7 with / WRO7. As a result, +5 V is applied to the Nth digit LED from the transistor array 8, only the Nth digit LED can be turned on, and only the Nth digit segment specified by the flip-flop 1 is turned on.

Such an operation is performed for each real time clock RTC. For example, if one digit is displayed after five digits, each digit is lit only for the period of the RTC, but all the digits are lit due to the afterimage phenomenon. Digits appear to be lit. Then, the mono multivibrator 5 is simultaneously activated by / WRO7. The cycle of this mono multivibrator 5 is RTC
Longer.

By the way, if there is an abnormality in the CPU and ▲ ▼ is not performed, the Q output of the mono-multi vibrator 5 becomes L after a predetermined time, the latch circuit 7 is cleared, and
LED will not be displayed.

However, in the present invention, as described above, the circuit configuration marked with a star in the figure, that is, the transistor array 8 (current output means) and the resistor 9 (current limiting resistor) are added. When not displaying all the LEDs, the Q bar output of the mono multivibrator 5
The 7-segment light emitting element 40, which is a specific LED, is energized so as to flow a normal current through the current limiting resistor 36 and the added current reducing resistor 9.

As a result, the CPU writes the alarm of the CPU to the mono-multi vibrator 5 so that it can be displayed on a specific LED even after the HALT stop.

In the drawing, the circles marked on the input and output of each element indicate the inversion of the signal phase there, Vcc is the DC power supply voltage, D1
D6 is a display number signal from the CPU to the 7-segment light emitting element (40 to 44), ▲ ▼ is a reset signal from the CPU to the flip-flop 1, 6 is an OR circuit, 51 is a resistor, and 52 is a resistor. Capacitors 30 to 36 are so-called LED current limiting resistors.

[Effect of the invention]

Thus, according to the present invention, the severity of the alarm display is increasing with the advancement of the system, and the alarm code is required in any failure mode. Therefore, the addition of a simple circuit configuration enables the alarm code at the time of an abnormal CPU stop to be reliably displayed on the LEDs without extinguishing the display of all LEDs, which is extremely advantageous in terms of cost, and It is clear from the LED display whether the device has stopped or the CPU has stopped abnormally, indicating a remarkable effect on improving the reliability of the display circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention. 1 Flip-flop 2,8 Transistor array 30-36 Current limiting resistor 40-44 7-segment light-emitting element 5 Monomultivibrator 51 Resistor 52 Capacitor 6 OR circuit 7 ... Latch circuit 9 ... Resistance.

Claims (1)

(57) [Scope of request for utility model registration] 1. A dynamic display circuit for performing a dynamic lighting display operation of a plurality of digits by a plurality of display elements based on a control signal from a CPU, and stopping the dynamic lighting display operation of a plurality of digits when the CPU is stopped. A current output unit that detects an abnormal stop of the CPU and outputs a current, and a current limiting resistor that is connected to a display element of a specific digit of the plurality of digits and that limits a current from the current output unit. When an abnormality occurs in the CPU, only the display element of the specific digit is statically lit, whereby the CPU
A dynamic display circuit for displaying an alarm indicating that an abnormality has occurred.