JPH01169501A - Switch signal reader - Google Patents

Abstract

PURPOSE:To neglect external noise and to accurately read out a switch signal by deciding the synchronism of a noise detecting signal with the output of a switch signal and reading out an output synchronizing with a noise detecting signal as a switch signal. CONSTITUTION:A noise detecting signal generating means 46 applies a noise detecting signal to the switch circuit 24. When a switch is in an OFF state, the noise detecting signal is not outputted from the circuit 24, but when the switch is turned to an ON state, outputted as a switch signal. If external noise is applied to an output line of the circuit 24, the noise is also outputted similarly to the switch signal. A synchronism deciding means 48 decides the synchronism of the noise detecting signal with the output of the circuit 24. A switch signal reading means 50 reads out an output synchronizing with the noise detecting signal in accordance with the decision. Thus, the switch signal can be accurately read out by neglecting the external noise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for reading switch signals while ignoring external noise.

2. Description of the Related Art In recent years, computer-applied equipment has become extremely popular and is used in various fields. All of these devices are equipped with a computer inside or outside, and the operating section is equipped with a switch circuit having keys and the like.

In such a switch circuit, when a key or the like is operated, chattering occurs in the switch signal. Therefore, a filter circuit 14 is usually interposed between the switch circuit 10 and the input/output board of the microcomputer 12, as shown in FIG. This filter circuit 14 consists of a resistor 16 that changes the voltage level of the switch signal from Hu to "[", a capacitor 18 that smoothes the signal voltage, and a Schmitt trigger integrated circuit 20 that shapes the waveform of the signal. Therefore, when the switch signal passes through the filter circuit 14, it is modified to remove the chattering, and the microcomputer 1
2 input/output port and is read by the CPU. As a result, if the operated key is, for example, a print key of a recorder, a predetermined process, such as recording measurement data on recording paper, is executed.

Problems to be Solved by the Invention However, in a switch signal reading device using such a filter circuit, if external noise, that is, noise caused by a strong external magnetic field, static electricity, etc., gets onto the output line of the switch circuit, , cannot be distinguished from the switch signal, resulting in malfunction.

For example, when the noise SO shown in FIG. 6B enters the input/output port (Ilo), the operation is the same as when the switch signal @S is input. By the way, the switch signal S has (a)
There is a switch-on operation that corresponds to a key operation as shown in the figure.

The present invention has been made in view of these conventional problems, and it is an object of the present invention to provide a switch signal reading device that can accurately read switch signals while ignoring external noise.

Means for Solving the Problems Means for achieving the above object will be explained below using FIG. 1 which clearly shows the present invention.

This switch signal reading device is equipped with a noise detection signal generating means 46 on the input side of the switch circuit 24 for supplying a noise detection signal to the switch circuit 24, and on the output side thereof, determining synchronization between the noise detection signal and the output of the switch circuit 24. The apparatus includes a synchronization determining means 48 and a switch signal reading means 50 for reading an output synchronized with the noise detection signal as a switch signal.

action The above means works as follows.

The noise detection signal generating means 46 provides a noise detection signal to the switch circuit 24. This noise detection signal is not output from the switch circuit 24 when the switch is in the off state, but is output as a switch signal when the switch is in the on state. At this time, if external noise is added to the output line of the switch circuit 24, that noise will also be output in the same way as the switch signal. The synchronization determining means 48 determines synchronization between the noise detection signal and the output of the switch circuit 24.

According to this determination, the switch signal reading means 50 reads the output synchronized with the noise detection signal as a switch signal.

Therefore, noise that is not synchronized with the noise detection signal will not be read as being indistinguishable from the switch signal.

Example Hereinafter, the present invention will be described in detail based on the accompanying drawings.

FIG. 2 is a circuit diagram showing the configuration of a switch signal reading device for a recorder to which the present invention is applied. In the figure, 22 is a recorder switch signal reading device, 24 is its switch circuit, 2
6 is a device equipped with a CPU. This switch circuit 24
is one of a number of switch circuits in the operation section of the recorder, and consists of a bush switch 32 with a key interposed between input and output lines 28 and 30, and a ground resistor 34 connected to its output line 30. . Note that a slide switch or the like may be used instead of the bush switch 32.

These input/output lines 28, 30 are connected to a device 26 equipped with a CPU, as well as an A-D converter that converts measured analog values such as voltage and current into digital values, and a recording device that records measured data.

The device 26 equipped with such a CPU includes, for example, a CPU.
<Central processing unit) 36, ROM (read-only memory)
38, a RAM (readable/writable memory) 40, an input/output port 42, a pass line 44, etc., is used. The CPU 36 corresponds to the central brain of the microcomputer, and according to instructions from the program, controls the entire system, performs arithmetic and logical operations, and temporarily stores the results.

It also controls peripheral devices. ROM3
8 is a control program for controlling the entire recorder;
A switch signal reading processing program and the like are stored.

Further, the RAM 40 stores data such as calculation results by the CPtJ 36. A switch circuit 24 is connected to the input/output port 42.
An input/output line 28, an A-D converter, a recording device, etc. are connected thereto.

The path lines 44 include address bus lines, data bus lines, control path lines, etc. for connecting them.

Next, the operation of this embodiment will be explained.

FIG. 3 is a flowchart comprising steps P1 to P4 showing an example of a switch signal reading processing program. In this program, first, Pl is the input/output port (Ilo>
It is determined whether there is an input to 42, that is, whether there is an output from the switch circuit 24. If YES, go to P2. I1 in P2
It is determined whether the 0 input is synchronized with the clock signal which is the noise detection signal. However, in order to make such a determination, the clock signal shown in FIG.
Input line 2 of the switch circuit 24 from the input/output port 42
I will send it out on 8th. Then, operate the key and press switch 3.
2 is turned on as shown in FIG. Therefore, I10
It is determined whether the input is synchronized with the I10 output by comparing the rising or falling edges of both pulses for an appropriate number of times. Y
In the case of ES, it is determined that the switch is on and the normal operation is performed, and the process is read and goes to P3. In P3, if the operated key is, for example, a print key of a recorder, a predetermined process is executed, such as recording measurement data such as voltage and current in waveforms on recording paper. If NO, the process goes to P4, where it is determined that the input is erroneous due to external noise, and the input is ignored. This is because (c) even if external noise CO as shown in the figure comes in, it will not synchronize with the clock signal. Note that not only the clock signal but also other signals that can be clearly distinguished from noise may be used as the noise detection signal.

Further, the noise detection signal is not necessarily sent out from the input/output port 42, but may be given to the input line 28 from another source.

According to the present invention, which has been described in detail, a switch signal can be accurately read while ignoring external noise.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a switch signal reading device according to the present invention. FIG. 2 is a circuit diagram showing the configuration of a switch signal @reading device for a recorder to which the present invention is applied. FIG. 3 is a flowchart showing a switch signal reading processing program used in the switch signal reading device. FIG. 4 is a diagram showing the correspondence between the operating states of the switches and the input/output states of the input/output ports in the switch signal reading device. FIG. 5 is a circuit diagram showing the configuration of a conventional recorder switch signal @reader. FIG. 6 is a diagram showing the correspondence between the operating states of the switches and the input states of the input/output ports in the switch signal reading device. 22...Switch signal reading device 24...Switch circuit 26...Equipped with CPU @ 28.30...
・Input/output line 32...Switch 36...CP
U42...Input/output port 46...Noise detection signal generation means 48...Synchronization determination means 50...Switch signal reading means

Claims (1)

[Claims] Noise detection signal generation means for supplying a noise detection signal to the switch circuit, synchronization determination means for determining synchronization between the noise detection signal and the output of the switch circuit, and switch signal reading means for reading the output synchronized with the noise detection signal as a switch signal. A switch signal reading device comprising: