GB2187012A - Data input device - Google Patents

Abstract

A data input device comprises a keyboard (6), a control unit (1), an input/output control data buffer (2), an input data buffer (3), an interface control circuit (4), a key state output circuit (5), a scanning address register (7), a symbol code memory (8), a key state detection circuit (9), a multiplexer (10), a key code output circuit (11) and an output data buffer (12). Keys of the keyboard (6) are each connected to the control unit (1) and to a respective input of the multiplexer (10). A clock signal from the control unit (1) is fed to the multiplexer (10) when a key is depressed. When that key is selected by the scanning address register (7), the multiplexer outputs a signal which is detected by the key state detection circuit (9). The key state detection circuit (9) controls operation of the key code output circuit (11) to read out a code, corresponding to the depressed key, from the symbol code memory (8), which code is stored in the output data buffer (12) for transmission to an external processing device via the interface control circuit (4). <IMAGE>

Description

SPECIFICATION Data input device This invention relates to a data input device such as a keyboard unit applicable in professional and personal computers, in micro- and mini-computers,terminal stations, operator desks, data preparation devices, specialized word processing devices and for the processing of economic information.

Awell known type of data input device is a keyboard unit having a keyboard and a control unit comprising scanning circuits and circuits for detecting a pressed or released key or button. The keyboard unit is unidirectionallyconnectedto an output buffer and to a connection circu it for connecting to a user's processing device such as a computer. An example of such a data input device is disclosed in Proceedings of the Scientific and Technological Conference on "Bulgarian Office Equipment - Structures, technologiesand Design", Silistra, 17-19 May 1978.

The disadvantages of such keyboard units are the inability to connect them to differenttypes of processing devices, the fixed layout and type of symbols on the keyboard, and limitations concerning the number of keys or buttons which can be pressed simultaneously.

According to the present inventionrthere is provided a data input device, comprising a keyboard, a control unit, an input/output control data buffer, an input data buffer, an interface control circuit, a key state output circuit, a scanning address register, a symbol code memory for storing codes corresponding to key symbols, a key state detecting circuit, a multiplexer, a key code output circuit, and an output data buffer; wherein the control unit is: bidirectionally connected via the input/output control data buffer to an external processing device; bidirectionally connected to the input data buffer; and unidirectionally connected to the external processing device, the keyboard, the interface control circuit, the key state output circuit and the scanning address register; the scanning address register is connected to the symbol code memory, the key state detecting circuit, and the multiplexer; the multiplexer has a plurality of inputs connected to respective keys of the keyboard, and an output connected to the key state output circuit, the key state output circuit having an output connected to the key state detecting circuit;; the key state detecting circuit has an output connected to an input of the key code output circuit, the key code output circuit having another input connected to the symbol code memory and an output connected to the output data buffer; and the output data buffer has an input connected to the interface control circuit, the interface control circuit being connected at an output to the external processing device and to the input data buffer.

An embodiment of the present invention may provide a data input device enabling the connection of processing devices to different types of interfaces, having any arbitrary layout of symbols on a keyboard of the data input device and having the ability to respondfullyto multiple depressed keys on the keyboard.

A data input device embodying the invention may comprise a control unit, bidirectionally connected to an input/output buffer for data control which is bidirectionally connected to an external processing device and a data input buffer, and unidirectionally connected to the processing device, to an interface control circuit, to a key state output circuit for outputting the state of a key or button of the data input device, and to a scanning address register.

The scanning address register is also connected to a symbol codememoryfordefininga keylayouton the keyboard, a ci rcuit which detects the state (depressed or released) of a key, and a multiplexer.

The inputs ofthe multiplexer are connected to the keyboard and the output of the multiplexer is connected to the key state output circuit, the output of which is connected to the key state detecting circuit.

The output of the key state detecting circuit is connected to the key code output circuit, and its input is connected to the symbol code memory which stores symbol codes and their layout on the keyboard.

Furthermore, the key code output circuit is connected to an output data buffer which is connected via the interface control circuit to the external processor and to the input data buffer, which is also connected to the processor.

An embodiment of the present invention may provide, in the interface control circuit, a shift register with parallel input and parallel and/or in-series output, information (data) inputs of which are connected to the output data buffer and control inputs of which are connected to the control unit, its outputs being connected to unidirectional data retrieval buffers. The outputs of the data retrieval buffers are connected to the processing device and their control inputs to the control unit.

An embodiment of the present invention may provide a data input device having a controllable interface, giving it the ability to modify the interface to enable the connection of different types of interfaces to external devices, the possibility of arbitrarily set- ting the symbol codes and their layout on the keyboard, and guaranteeing full operation even when a number of buttons are depressed simultaneously.

Reference is now made, by way of example, to the accompanying drawings illustrating an embodiment of a data input device in accordance with the present invention. In the Figures: Figure 7 shows the circuitry of the data input device; and Figure2shows a structural diagram of an interface control circuit.

Referring to Figure 1, the data input device comprises a control unit 1, which is bidirectionally connected along a data bus to an external user's processing device, via an input/output control data buffer 2. The control unit 1 is also connected bidirectionally to an input data buffer 3, and there is further provided a unidirectional connection (interruption line 20) direct from the processing device into the control unit 1. Unidirectional connections extend from the control unit 1 to an interface control circuit 4, a key state output circuit (enabling circuit) 5, a keying means 6 such as a keyboard orkeypad equipped with keys and/or buttons (henceforth, keyboard), and a scanning address register 7.

The scanning address register 7 is connected to a symbol code memory 8 which stores the arrangement of symbols on the keys of the keyboard 6, to a key state determination circuit 9, and to a multiplexer 10. The multiplexer 10 has inputs connected to re- spective keys ofthe keyboard 6, and an output connected to the key state enabling circuit 5. The output ofthe key state output circuit 5 is connected to an input of the key state determination circuit 9, whose output is connected to a key code output circuit (enabling circuit) 11. The key code output circuit receives another input from the symbol code memory 8, and provides an output to an output data buffer 12.

The output data buffer 12 provides an output to the interface control circuit4, whose output is fed both to the external processing device to the input data buffer 3.

The control unit (Figure 1) comprises a clock pulse generator 13, a microprocessor 14, a permanent store 15, a primary memory 16, and an address decoder 17. The output of the clock pulse generator 13 is fed to the keyboard 6 and to the microprocessor 14, which by means of address busbars is connected to the permanent store 15, the primary memory 16, the scanning address register 7 and the address decoder 17. The address decoder 17 is connected in turn to the scanning address register 7, to the key state output circuit 5, to the interface control circuit 4, to the input data buffer 3 and to the input-output buffer 2. The microprocessor is further connected by means of data busbars to the permanent store 1 the primary memory 16, the input data buffer 3 and the input-output control data buffer 2.

The interface control circuit 4 (Figure 2) comprises a shift register 18, the data inputs of which are connected to the output data buffer 12, and a control inputofwhích is connectedto the control unit 1. The outputs of the shaft register 18 are connected to unidirectional data retrieval buffers 19, which have con- trol inputs connected to the control unit 1, and outputs connected to the input data buffer3 and to the external processor.

The operation of the data input device is as follows. The clock pulse generator 13 emits a series of clock pulses which enter one of the contacts of each key or button on the keyboard 6. The other contact of each key is connected to a respective inputofthe multiplexer 10. In this way a signal is fed through, whilst a key is depressed,to the respective input of the multiplexer 10; after the key is released, no signal is fed through to the multiplexer. Switching of the multiplexer 10's inputs to its output is achieved by means of a scanning address which the control unit 1 records in the scanning address register 7 and continually updates. The recording of each subsequent scanning address is done by a control signal from the control unit 1.In this way control unit 1 performs scanning in a consecutive, or preselected or random orderofallthekeysonthe keyboard 6.

Wheneverthe currently-scanned key is depressed, there is a closed connection from the clock generator to the input of the multiplexer 10 selected by the scanning address, and so a key-presssignal istrans- mitted through the key state output-circuitS to the key state determining circuit 9. The key state detecting circuit 9 determines, on the basis of the scanning address, what is the currently selected key at that moment, and it updates information on the current state ofthat key on the basis of the information arriving from multiplexer 10 to indicate either a depressed or released key.Each button mistaken to be depressed (or released) when it has been detected as depressed (or released) during two consecutive scannings, the time between which is determined by the time required for attenuation of the mechanical oscillations of the contact system of the key or button. Thus, a signal indicating either a depressed or released key is provided at the output of the key state detecting circuit 9.

It should be noted that by this method of detecting the depression of a key on the keyboard, it is possible for the data input device to correctly respond to key depressions even when several keys are depressed simultaneously.

The key state signal from the key state detecting circuit 9 is sent to the key code output circuit 11, and causes the transmission of a code corresponding to that key to the output data buffer 12. The code ofthe selected key has been previously stored in symbol memory8forsetting a desired setofsymbols and a desired arrangement ofthose symbols on the keyboard 6. Asymbol code is recorded in this memory8 for each scanning address. Itis possible to alterindividual codes,forchanging specific symbols on the keyboard orforchanging the layout of symbols on the keyboard, by means of re-recording the data stored in this memory 8. Of course, it is also desirable to change the symbols marked on the keys of the keyboard accordingly.

Afterthe code corresponding to the currentlyselected key is found, and it has been determined whether the key is pressed down or released, the code is recorded in the output data buffer 12 from which it is fed to the interface control circuit 4. Under control of a signal from the control unit 1, the code is stored in the shift register 18 whence it is fed to the external processor via unidirectional data retrieval buffers 19 The data retrieval buffers 19 may be arranged either in series or in parallel, depending on the type of interface provided in the external processing device. The data retrieval buffers 19 are also controlled by a signal from the control unit 1. The control unit 1, by means of input data buffer 3, is able to receive the data transmitted from the data retrieval buffers, and hence to follow the transmission process in the interface to the external processing device.

The data input device provides a controllable inter facetothe user's processing device which can contain bidirectional data busbars, bidirectional control data busbars and an input interrupt line. The data busbars are buffered to the user's interface by means ofthe data retrieval buffer 19, and by the input data buffer3 to the control unit 1. The control data busbars (commands, state) are buffered by means of the input-output control data buffer 2. An interrup tion line 20 from the user's device connects directly to the control unit 1. This enables operation of the data input device to be carried out in cooperationn with the external processor either by internal synchronisation or by following an external clocksignal provided by the external processor.

As mentioned above, a data input device embodying the present invention comprises a keyboard (6), a control unit (1), an input/output control data buffer (2), an input data buffer (3), an interface control circuit (4), a key state outputcircuit (5), a scanning address register (7), a symbol code memory (8), a key state detection circuit (9), a multiplexer (10), a key code output circuit (11) and an output data buffer (12).

Keys of the keyboard (6) are each connected to the control unit (1 ) and to a respective input ofthe multiplexer (10). Aclocksignal from the control unit (1) is fed to the multiplexer (10) when a key is depressed.

When that key is selected by the scanning address register (7), the multiplexer outputs a signal which is detected by the key state detection circuit (9). The key state detection circuit (9) controls operation of the key code output circuit (11 ) to read out a code, corresponding to the depressed key, from the symbol code memory (8), which code is stored in the output data buffer (12) for transmission to an external processing device via the interface control circuit (4).

Claims (7)

1. A data input device, comprising a keyboard, a control unit, an input/output control data buffer, an input data buffer, an interface control circuit, a key state output circuit, a scanning address register, a symbol code memory for storing codes corresponding to key symbols, a key state detecting circuit, a multiplexer, a key code output circuit, and an output data buffer; wherein the control unit is: bidirectionallyconnectedvia the input/output control data buffer to an external processing device; bidirectionally connected to the input data buffer; and unidirectionally connected to the external processing device, the keyboard, the interface control circuit, the key state output circuit and the scanning address register; the scanning address register is connected to the symbol code memory, the key state detecting circuit, and the multiplexer; the multiplexer has a plurality of inputs connected to respective keys of the keyboard, and an output connected to the key state output circuit, the key state output circuit having an output connected to the key state detecting circuit; the key state detecting circuit has an output connected to an input of the key code output circuit, the key code output circuit having another input connected to the symbol code memory and an output connected to the output data buffer; and the output data buffer has an input connected to the interface control circuit, the interface control circuit being connected at an output to the external processing device and to the input data buffer.

2. A data input device as claimed in claim 1, wherein the interface control circuit comprises a shift register and a plurality of data retrieval buffers, the shift register having parallel inputs connected to the output data buffer, control inputs connected to the control unit, and parallel outputs or a serial output connected to the data retrieval buffers, and the data retrieval buffers having control inputs connected to the control unit and parallel outputs or a serial output connected to the external processing device and to the input data buffer.

3. A data input device as claimed in claim 1 or2, wherein the control unit comprises an address dec oder for supplying address information to the input/ output control data buffer, the input data buffer, the interface control circuit, and the scanning address register.

4. A data input device as claimed in claim 1, or 3, wherein the control unit comprises a clock gener atorfor supplying a clock signal to the keyboard.

5. Adata input device as claimed in claim 1 or2, wherein the control unit comprises an address decoder, a clock generator, a microprocessor, a permanentstore, and a primary memory.

6. Adata inputdevice as claimed in claim 1, wherein the interface control circuit has a shift registerwith input in parallel and output in parallel and in series, its information (data) inputs being connected to the output data buffer and its control inputs being from the control unit and its outputs are connected to the unidirectional buffers for data retrieving which by input are connected to the control unit and by output to the input data buffer and the user's device.

7. A data input device, substantially as herein before described with reference to the accompany- ing drawings.