JPH04331398A - Timer - Google Patents

Abstract

PURPOSE:To eliminate error due to delay time in filter process of a timer provided with a filter for removing noise which is given an external input signal, and obtain a high accuracy timer not affected by noise. CONSTITUTION:Regardless of normal start signal or noise, if an external input signal is given, timer motion 20 is started immediately. If it is judged 21 not to be normal start signal based on filter output, the timer motion is reset 22. If it is judged to be a normal start signal, the timer motion 20 is continued.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to timers, and more particularly to a high-precision timer equipped with a filter for removing noise from an external input signal input to start timer operation.

0002

[Prior Art] Generally, when a timer receives a regular start signal, it starts its operation, compares the elapsed time from this starting point with a preset time, and calculates the elapsed time as the set time. It is configured to time up and output a timer output when the timer matches the signal, and also removes noise from the external input signal to prevent the start of the timer operation from being caused by noise that is not a legitimate start signal. The timer operation is started after the processing by this filter is completed and the external input signal is determined to be a regular start signal. This filter is composed of, for example, a CR filter consisting of a resistor and a capacitor or a digital filter using software processing.

0003

[Problem to be solved by the invention] In this way, conventionally,
Since the timer operation starts after the processing in the filter is completed, the delay time caused by the filter, generally several ms to several tens of ms, becomes an error, which is an obstacle to improving the precision of the timer. ing.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a highly accurate timer that eliminates errors due to delay time caused by filters and is not affected by noise.

[0005]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention is constructed as follows.

That is, the present invention provides a timer provided with a filter for noise removal to which an external input signal is applied, which includes a timer that immediately starts the timer operation in response to the external input signal, and a determining means for determining whether or not the external input signal is a regular start signal based on the filter output; and based on the output of the determining means, when the external input signal is not a regular start signal, and reset means for resetting the timer operation of the time measuring means.

[0007]

[Operation] According to the above configuration, regardless of whether the external input signal is a regular start signal or noise, when the external input signal is applied, the timer operation is immediately started and the external input signal is applied. Based on the output of the filter, when it is determined that the start signal is not a regular start signal, the timer operation is reset, and when it is determined that the start signal is a regular start signal, the timer operation is continued.
Therefore, the delay time caused by the filter does not become an error unlike in the conventional case, and malfunctions due to noise can also be prevented.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram of a timer according to an embodiment of the present invention. Timer 1 of this embodiment includes an input circuit 2 to which various external input signals for control are applied, and a circuit for setting set values and modes. a key switch circuit 3 for the purpose of
It includes a CD reference voltage generation circuit 7, an LCD display 8, an output circuit 9 for timer and batch, a power supply circuit 10, a battery 11 for compensating operation when no power is applied, and a power failure detection circuit 12. There is.

The signal processing circuit 4 includes a ROM 13 and a RAM.
14, an LCD driver 15, and a CPU 16.

The input circuit 2 has a noise removal filter 17 to which an external input signal such as a start signal is applied, as in the conventional case, and this filter 17 is connected to a resistor 18 as shown in FIG. and a capacitor 19.

The output of this filter 17 is applied to the terminal 16b of the CPU 16 as in the conventional case, and in this embodiment, an external input signal is applied directly to the external interrupt terminal 16a of the CPU 16 without passing through the filter 17. It has become.

The signal processing circuit 4 of this embodiment has an external interrupt terminal 16 as shown in the functional block diagram of FIG.
counting basic clock pulse signals obtained by dividing the clock pulse signal generated by the system clock generation circuit 6 immediately activated by an external input signal input to a;
When the count value reaches the main setting value set by the key switch circuit 3, the clock means 20 drives the output circuit 9 to output a timer output, and the output of the filter 17 given to the terminal 16b is input to the external input signal. a determining means 21 for determining whether or not the filter continues even after the filter time has elapsed, that is, whether or not the external input signal is a regular start signal;
Based on the output of the discrimination means 21, if the start signal is a regular start signal, the timer operation by the timer means 20 is allowed to continue; if it is not a regular start signal but a noise, the timer operation by the timer means 20 (timekeeping operation) is allowed. )
It has a function as a reset means 22 for resetting the .

FIG. 4 is a flowchart of such control.

First, the process is started by inputting an external input signal (step S1), and a timing operation (timer operation) is immediately started (step S2), and a filter counter for measuring filter time is activated (step S3). .

[0016] Waits for a time equal to the filter time set in the filter 17 plus a predetermined time α (step S
4), it is determined whether the output of the filter 17 continues (step S5), and if it continues, it is assumed that the external input signal is a regular start signal, and the timing operation (
The timer operation continues (step S7), and when the set time is reached, the timer output is output.

In step S5, if the output of the filter 17 is not continuing, it is assumed that the external input signal is not a regular start signal, and the timing operation (timer operation) is performed.
(step S6), and prepares for inputting the next external input signal.

In this way, since the timing operation is performed immediately in response to the input of the external input signal, the delay time caused by the filter 17 does not cause an error in the timer 1, and moreover,
When the external input signal is noise, the time measurement operation is reset based on the output of the filter 17, so that it is not affected by noise.

[0019]

As described above, according to the present invention, regardless of whether the external input signal is a regular start signal or noise, when an external input signal is given, the timer operation is immediately started, and the filter When it is determined that the start signal is not a regular start signal based on the output of There is no time error, and malfunctions due to noise can be prevented, making it possible to realize a highly accurate timer.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a configuration diagram of a filter in the input circuit of FIG. 1;

FIG. 3 is a functional block diagram of the present invention.

FIG. 4 is a flowchart for explaining the operation.

[Explanation of symbols]

1 Timer 2 Input circuit 4 Signal processing circuit 17 Filter 20 Timekeeping means 21 Discrimination means 22 Reset means

Claims (1)

[Claims] 1. A timer comprising a noise removal filter to which an external input signal is applied, the timer comprising a timer for immediately starting a timer operation in response to the external input signal, and an output of the external input signal and the filter. a determining means for determining whether or not the external input signal is a regular start signal, based on the output of the determining means; A timer comprising: a reset means for resetting the timer operation.