JPS58184631A - Keyboard reading method - Google Patents

Abstract

PURPOSE:To perform secure detection in a short time, by storing key-stroke data obtained by performing a line-by-line scan on a keyboard having a matrix arrangement previously, and starting the 2nd scan at a line where a key-stroke is detected. CONSTITUTION:A CPU starts reading a keyboard input by an interruption signal Pt from a timer TC4, performs a successive scan on scanning lines S0-S7 to apply detected pulses, and fetches return data obtained from return lines R0-R7. Once the scan is executed once, a signal Pa is applied to the timer TC4 and the return data are stored in an RAM. When the interruption signal Pt is applied, the CPU reads the return data stored last and starts a scan at a scanning line corresponding to the data. Then, the period of the interruption signal Pt is set more than a debounce time. Consequently, the accurate detection is performed in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reading keyboard input signals in a device using a microprocessor.

Generally, a keyboard is used as an input device in devices using a microprocessor.

In this case, the method for reading keyboard input signals is as follows:
It generates an interrupt in the microprocessor, scans and monitors the contact status of the keyboard, and uses the response to determine whether a key has been pressed and reads it. At this time, in order to improve the reliability of reading, a method is used in which the keyboard scan is repeated twice or more, and when the data matches, it is read as an input signal. However, this method has the disadvantage that since the keyboard is always scanned in the same order, it takes a long time to detect a data match, that is, it takes a long time to interrupt the microprocessor.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a keyboard reading method that eliminates the drawbacks of the conventional methods as described above and can efficiently scan the keyboard and shorten the time required to interrupt the microprocessor.

The keyboard reading method of the present invention temporarily stores data obtained in response to keyboard presses when the keyboard is scanned, and in the next scan, starts scanning from the key whose press was detected last time. , the time required to detect data matching is shortened, and the interrupt time to the microprocessor is shortened.

Hereinafter, the keyboard reading method of the present invention will be explained using the drawings.

FIG. 1 is a block diagram showing an embodiment of a keyboard reading device to which the keyboard reading method of the present invention is applied. In the figure, CPU is a microprocessor, TCL is a timer that applies an interrupt signal Pt to the microprocessor CPU to start scanning, KEY is a keyboard,
SO~S7 are scan lines to which a detection pulse is applied to detect the pressed state of the keyboard KEY, and RO~
R7 is a return line in which return data :: is generated according to the pressed state of each key in response to the detection pulses applied from the scan lines SO to S7. Further, on the keyboard KEY, keys are arranged at the intersections of the scan lines SO to S7 and the return lines RO to R7, respectively.

The operation of the keyboard reading device configured as described above is as follows. Microprocessor CP
When U is applied with the interrupt signal Pt from the timer TCL,
The reading operation of the keyboard input is started, scan lines SO to S7 are sequentially scanned and detection pulses are applied, and return data obtained from return lines RO to R7 is taken in.

Furthermore, when one scan is completed, an end signal Pa is generated and applied to the timer TCL. FIG. 2 is a time chart showing this state, in which the timer TCL generates an interrupt signal Pt at regular time intervals, and the interrupt signal Pt is a termination signal Pt from the microprocessor CPU.
It is reset by a.

Now, when one scan is completed and the return data corresponding to the press of any key is obtained, the microprocessor CPU stores this return data in RAM etc. and generates the end signal Pa, and then the next scan is performed. Interrupt signal P
wait for t. After this, when the next interrupt signal f't is applied, the microprocessor CPU reads out the previously stored return data and starts scanning from the scan line corresponding to that data. Therefore, if the same key was pressed during the previous scan, the return data will match on the first selected scan line, and the keyboard input signal will be read at that point, and the scan will begin. ends.

Therefore, there is no need to scan subsequent scan lines, and the time that the microprocessor CPU is occupied for reading keyboard input can be shortened.

Here, the period at which the interrupt signal Pt is generated is called a debounce time, and is set in consideration of prevention of chattering in the keyboard KEY. That is, by detecting the pressed state of the keyboard KEY at time intervals equal to or longer than the debounce time, the influence of chattering at the key contacts can be removed.

In addition, in the above explanation, the case where one scan is performed within the debounce time is exemplified, but the scan interval is not limited to this, and the scan is repeated at a constant cycle regardless of the debounce time, and the return A similar operation can be performed by comparing data obtained at different debounce times. In this way, the debounce time is determined depending on how many times the comparison is performed,
The debounce time can be set by software on the microprocessor CPU side.

As explained above, in the keyboard reading method of the present invention, when the keyboard is scanned in response to an applied interrupt signal, data obtained in response to keyboard presses is temporarily stored, and Since the scan is started from the key whose press was detected last time, the time required to detect data matching is shortened, and the time required to interrupt the microprocessor can be shortened.

[Brief explanation of the drawing]

Figures 11 and 2 show - correction of implementation procedure - (method) of a keyboard reading device to which the keyboard reading method of the present invention is applied. 1. Indication of the incident: Patent Application No. 57-66625 2,
Title of the invention Keyboard reading method 3, relationship with the person making the amendment Applicant address 2-9 Nakamachi, Musashino-shi, Tokyo Name (670) Yokoretsu Electric Manufacturing Co., Ltd. 4, Agent

Claims (1)

[Claims] A keyboard in which multiple keys are arranged in a matrix is scanned line by line to obtain return data according to the pressed state of the keyboard, and this scanning is repeated and when the return data matches, the return data is converted into a key human input signal. In the keyboard reading method, the return data obtained in response to the keyboard press is temporarily stored when the keyboard is scanned, and when the keyboard is scanned, the return data obtained in response to the keyboard press is temporarily stored. A keyboard reading method characterized by starting scanning from .