JPS6010325A - Key scanning system - Google Patents

Abstract

PURPOSE:To improve the reliability by discriminating it as the presence of key input when the key input is detected as absence, presence, and presence. CONSTITUTION:Presence/absence information of key switch depression is inputted to a shift register SR (0) at each prescribed time, and the shift register is shifted from (0) to (2) in order. Thus, the oldest information is stored in the (2) and the newest information is stored in the (0). Since the shift registers SR (0) and (1) are connected to inputs of an AND logic circuit LG1, when they are both logical 1, an exclusive OR circuit LG2 goes to logical 1. Since other input of an exclusive OR LG2 is connected to the shift register SR (2), when this input is logical 0, logical 1 is outputted to an output OUT. Thus, when the key input is present, the key input just before is present and further, the preceding key input is absent, then the output terminal OUT goes to logical 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to a key scan method that reliably determines whether or not there is any human power on a key when operating a key switch provided on a keyboard.

(2) Prior art and problems The one connected to the central processing unit CPU and called the numeric keypad
A keyboard that inputs numbers using 0 keys, or 1
Keyboards for inputting numbers using zero or more keys are well known. As shown in Figure 1, this means that the bus from the central processing unit is connected to the digital output DO and digital input
are connected to each other, and are provided with four output lines DO to D3 and input lines po to p3, respectively. Also DO~D3 and PO
~P3 are orthogonal to each other, a key switch is connected to the intersection point, and they are labeled as Of, 02-, and D
O to D3 are connected to a positive power supply via a pull amplifier resistor. D3. D2. “11” on each line of DI and DO
Apply a 10'' pulse and check the outputs of PO to P3.

When no key switch on the DO line is pressed, all outputs of PO-P3 become "1111". When there is a pressed key, the output at that position becomes "O". At the next timing, "1101" is applied to check whether or not a key on the D1 line has been pressed. Furthermore, it sequentially sends "1011" and "0111", and during the first round, it sees "O"1" of PO-P3, knows the position of the key to be pressed, and presses the key with the ° code assigned in advance. Key The chattering lasts about 3 milliseconds, so a filter may be used to prevent this or to prevent malfunctions due to noise.However, due to the characteristics of chattering and the habits of the operator, the filter used may be It had the drawback of not being sufficiently effective considering its size and price.

(3) Object of the Invention An object of the present invention is to improve the above-mentioned drawbacks and to provide a key scanning method that repeats key scanning at predetermined time intervals and reliably determines whether or not the key is operated manually.

(4) Structure of the Invention The structure of the present invention to achieve the above-mentioned object is to determine whether or not a key is pressed based on changes in the pulses received by the central processing unit, which sends pulses to the key switches of the keyboard at predetermined time intervals. In the key scan method, when it is determined that the key is powered at the time, the previous two states are referred to, and if the previous state is that the key is not powered, the key is powered, or the key is powered, the key The final decision is whether human labor is required.

(5) Embodiment of the Invention FIG. 2 is a diagram showing the configuration of an embodiment of the invention, which is inserted between the digital input section DI of FIG. 1 and the central processing unit CPU. SR is stored in a shift register for a predetermined time (for example, 10
Information on whether or not the key switch is pressed is stored every millisecond (milliseconds), and shifted sequentially in the direction of the arrow. Therefore, (2) stores the state two scan times ago, (1) stores the previous state, and (0) stores the current state. When there is a key switch input in the shift register (0), that is, when the switch is pressed, the presence or absence of an output from the second logic operation circuit LG2 is checked. It is the first logic operation circuit L when both (0) and (1) have input.
The output of GI becomes "1", and (2) shows the output OU of the second logic operation circuit LG2 (exclusive OR circuit) when it also serves as an input.
T becomes "1". Therefore, the output OUT of LG2 becomes "1".
”, there is currently a switch input, the previous time there was a switch input, and the previous time there was no switch input.In that case, the output of the logic circuit LG2 is used to send the current switch input to the central processing unit CPU. Take in.

FIG. 3 shows a flowchart in a case where the above operations are executed by software as another embodiment of the present invention. When it is determined that there is no key press, the key signal is set to FF, and when it is determined that the key is pressed, the key signal is set to that number. Let the key signal of the latest scan be the key (0), the key signal of one cycle before (one scan before) be the key (1), and the key signal two cycles ago be the key (2).

Initially, it is determined whether the key (0) is FF. If yes, there is no key personnel available, so the decision is over.

If it is not FF, it means that the key has been pressed for the first time or has been pressed continuously from before, so proceed to the next step.

It is determined whether the key signal (2) is FF. If the answer is no, the decision is over and the decision is over. If YES, it is determined whether the key signal (0) is the same as the key signal (1). If YES, a key flag F is set to capture the key signal. If no, there is a possibility of malfunction, so the process is terminated.

6) Effects of the Invention As described above, according to the present invention, it is possible to reliably determine whether or not a key press operation has been performed using relatively simple means, thereby increasing reliability in information processing.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating key signal extraction by key scanning, FIG. 2 is a partial diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is an operational flowchart of another embodiment of the present invention. Do...-Digital output section Dl--Digital input section SR...Shift register Patent applicant Fujitsu Limited Agent Patent attorney Eisuke Suzuki

Claims (1)

[Claims] In the key scanning method, in which the central processing unit, which sends pulses to the key switches of the keyboard at predetermined intervals, determines whether there is human key force based on changes in the received pulses, if it is determined that there is human key force at the time of 1, then the previous 2 The key scan method is characterized in that, by referring to the previous state, when the previous state is that the key is not powered, the key is powered, or the key is powered, it is finally determined whether the key is powered.