JPH0610425Y2 - Keyboard controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention selectively drives a row of a key switch matrix by using an input / output port of a one-chip microcomputer. The present invention relates to a keyboard controller for detecting the on / off state of a key switch by inputting a row signal of

<Prior Art> Generally, when controlling a keyboard composed of key switches arranged in a matrix, a general-purpose 1
Often a chip microcomputer is used.

At this time, a plurality of input / output port circuits of a general-purpose microcomputer as shown in FIG. 2 are used. This input / output port circuit is composed of a signal output section o composed of a D flip-flop circuit f, an input buffer b, a NAND gate and an output driver circuit, and detailed description of the operation will be omitted. Accordingly, it can be used as an input port or an output port according to the data given through the internal bus B.

That is, when "L" is output to the internal bus B and latched by the D flip-flop circuit f at the timing of the clock pulse CL "H", the Q terminal output is "L" and the Q terminal output is "L".
H ″, the p-channel semiconductor element z1 is off, the n-channel semiconductor element z2 is on, and the p-channel semiconductor element z is
3 is turned off, and the port P output becomes "L".

On the other hand, when "H" is output to the internal bus B, the clock
The pulse CL "H" causes the D flip-flop circuit f to have a Q terminal output "H" and a Q terminal output "L", and the p-channel semiconductor element z1 is on during the clock pulse CL "H" and is an n-channel semiconductor. The element z2 is turned off, the p-channel semiconductor element z3 is turned on, and the port P output becomes "H".

When such an input / output port P is used as an input port, the input buffer b is enabled, and the n-channel semiconductor element z2 is turned off to input an external signal.

Utilizing the functions as described above, a plurality of input / output ports P are used to input the row signal of the key switch matrix to detect the on / off state of the key switch.

<Problems to be Solved by the Invention> However, when such an input / output port P is used as an input port, noise is mixed into the clock pulse CL to generate a pulse CL “H”, and If the signal state of the internal bus B, which is also used for the purpose, happens to be "L", the n-channel semiconductor element z2 is turned on and the port P output is held "L" and fixed, as described above. May be.

Then, the signal "L" is continuously applied to the input buffer b of this input port, and as a result, it seems that even the unpressed key switches on the keyboard are being pressed, which causes the malfunction. May be.

The following points can be cited as the cause of the external noise being superposed on the clock pulse CL given to the input / output port circuit used as the keyboard controller.

Electrostatic noise is more likely to occur than static electricity charged on the human body when the operator presses the key switch.

The row wiring of the key switch matrix usually has a long wiring length and high impedance and is easily affected by external noise.

As for the wiring pattern, the wiring pattern can be improved by using a double-sided wiring printed board, but the cost is increased. In the case of a keyboard, a single-sided wiring printed board is generally used because of the demand for cost reduction.

The problem to be solved by the present invention is that even if the above-mentioned transient external noise is generated, the key
The purpose is to detect a switch on / off state, and to realize a keyboard controller that can perform smooth operation.

<Means for Solving Problems> In the present invention which solves the above problems, the signal “L” on the internal bus is latched by the clock pulse “H” and its port output becomes “L” and becomes an output port. A signal "H" on the internal bus is latched by the clock pulse "H" to set its port output to "H", and at least two input / output ports serving as input ports by enabling an input buffer are provided. Using a chip microcomputer, each of the columns of the key switch matrix is selectively driven by the output "L" with the input / output port as the output port, and the input / output port as the input port. In a keyboard controller for detecting ON / OFF of a key switch by inputting a signal generated in each row of a matrix, the key switch A counter is provided which counts the key switches in the ON state during the column driving operation of the switch matrix and outputs a carry signal to the one-chip microcomputer when the counter value exceeds a certain value. When the carry signal is applied, the input buffer is valid and "H" is applied to the internal bus corresponding to the input / output port that is the input port, and the clock pulse is set to "H". Is a keyboard controller characterized by starting a column scan operation using as an input port.

<Operation> The keyboard controller of the present invention uses the input / output port of the one-chip microcomputer to sequentially drive the columns of the key switch matrix to input the row signal, and to determine the number of the key switches in the ON state. Counting is performed, noise is considered to have occurred when the number of counts exceeds a certain value, control is once made to output "H" level from the row input port, and the row input port is returned to the correct input port. Then, the column driving operation is started again.

<Embodiment> FIG. 1 is a diagram showing an example of a keyboard controller embodying the present invention.

In the figure, reference numeral 1 is a general-purpose one-chip microcomputer CPU, which has input / output ports P10, P11, P20,
Input / output ports P10 and P11 are used as row c0 and c1 input ports of the key switch matrix 2 and input / output ports P20 and P21 are used as column select signal output ports of columns r0 and r1.

Reference numeral 2 denotes a key switch matrix, and four key switches sw00, sw01, sw10, sw11 are arranged at each intersection of row c and column r for the sake of simplicity.

Reference numeral 3 is a counter connected to the CPU 1. CPU1
Outputs a pulse from the terminal Pout when a key switch in the ON state on the key switch matrix 2 is detected, the counter 3 counts this pulse, and when the counter value exceeds a certain value, the CPU outputs from the terminal C to the CPU 1 The carry signal is output to the Cin terminal of. This counter 3 is CP
When the column drive of the key switch matrix of U1 has completed one cycle, the reset reset signal is given from the CPU1.

Input / output ports P10, P11, P2 in the CPU 1
The configurations of 0 and P21 are similar to those of the input / output port circuit shown in FIG.

Now, the keyboard controller of the present invention thus constructed operates as follows.

The CPU 1 normally outputs a column drive select signal "L" from the output ports P20, P21 to selectively drive each column of the key switch matrix 2 sequentially as r0, r1, r0, .... When the column drive select signal is output and the drive of the column is settled, the on / off state of the key switch installed in the column input from the input ports P10 and P11 is checked. By repeating this operation, it is possible to detect all on / off states on the key switch matrix 2.

At this time, the CPU 1 outputs a pulse from the terminal Pout each time the key switch in the ON state is detected. The counter 3 counts this pulse output, and the reset signal RESET provided when the column driving operation of the CPU 1 completes one cycle.
It is reset by and the count operation becomes possible again.

Therefore, the counter 3 holds the number of key switches in the ON state. Then, when the counter value exceeds a predetermined value, for example, the number of columns, a carry signal is output to the terminal Cin of the CPU 1.

When the carry signal is input, the CPU 1 causes the internal bus B to "H" by the firmware set in advance.
And clock pulse CL “H”,
The input ports P10 and P11 are controlled to output "H" level.

That is, noise is generated at one of the input ports,
The "L" level output is fixed, and it is determined that the correct key switch operation cannot be read out, and the function of these input / output ports as the input port is restored.

Then, after that, the scan of the key switch matrix 2 is started again.

For example, when the row cO becomes the “L” level due to the influence of transient noise, these key switches sw01, sw01, sw01, irrespective of the on / off states of these switches.
It looks like sw11 is on, but at this point counter 3
When a carry signal is output from the CPU 1, the CPU 1 once outputs "H" level to the ports P10 and P11, and then the key switch matrix 2 starts to scan, and the key switch matrix scan operation is newly started. can do.

In the example shown in this figure, the external circuit, that is, the counter 3 is used as the function of counting the key switches in the ON state of a certain value or more, but it can be realized by software using the counting function of the CPU 1. it can.

In this way, the keyboard controller of the present invention detects that the key switch of a certain value or more is turned on during the column drive select operation, and the CPU once outputs the “H” level to the input port. The influence of noise can be eliminated by setting the scan operation start state.

<Effects of the Invention> The keyboard controller of the present invention uses the input / output ports of the one-chip microcomputer to sequentially drive the columns of the key switch matrix to input the row signals and to turn on the key switches in the ON state. The number is counted, and when the counted number exceeds a certain value, it is considered that noise has occurred, and once the row input port is output "H" level and the column driving operation is restarted, transient noise occurs. Also, the on / off state of the key switch can be detected without being affected by this, and a keyboard controller that operates smoothly can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a keyboard controller embodying the present invention, and FIG. 2 is a configuration diagram of input / output ports of a general-purpose one-chip microcomputer. 1 ... Central processing unit CPU, 2 ... Key switch matrix, 3 ... Counter.

Claims (1)

[Scope of utility model registration request] 1. A signal "L" on an internal bus is latched by a clock pulse "H" and its port output is set to "L" to become an output port. The signal "H" on the internal bus is clock pulsed. It has at least two input / output ports that are latched at "H" to set the port output to "H" and enable the input buffer to become input ports.
Using a chip microcomputer, each of the columns of the key switch matrix is selectively driven by the output "L" with the input / output port as the output port, and the input / output port as the input port. In a keyboard controller for detecting ON / OFF of a key switch by inputting a signal generated in each row of the matrix, the key switch in the ON state is counted during the column drive operation of the key switch matrix, and a counter value is obtained. Is provided with a counter that outputs a carry signal to the one-chip microcomputer when
The one-chip microcomputer applies "H" to the internal bus corresponding to the input / output port which is the input buffer and is the input port when the carry signal is applied, and the clock pulse is applied. A keyboard controller characterized in that a column scan operation is started by setting the input / output port to "H" and using the input / output port as an input port.