GB2121224A - Function keyboard for a microprocessor system - Google Patents

Abstract

A self-contained add-on device (1) which may be connected into a general purpose computer system to provide an array of dedicated function keys (7). A single press of a key (7) on the device (1) will generate a sequence of data codes. The sequence associated with each key can be of any length pre-defined either during manufacture of the device or by the user using the device's own keys in a special programme mode. The device has provision for connecting into an existing computer system (VDU, CPU) having a keyboard, without affecting any existing data transfers between components in the computer system (via line 15), in such a way that the code sequences generated by the add- on device are interpreted by the computer system as if they had originated at the existing computer keyboard. <IMAGE>

Description

SPECIFICATION Function keyboard for a microcomputer system BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an add-on device which may be connected into a general purpose microcomputer system to provide a keyboard of dedicated function keys. This is a facility not normally available on general purpose keyboards.

The device is particularly useful when general purpose microcomputers are being used as word processors.

2. Description of the Prior Art Many general purpose microcomputer systems consist of a visual display unit (VDU), a central processing unit (CPU) and a printer. Each of these units is connected by a length of cable wired to conform to one of many interface standards. The most common standard for the connection of the VDU to the CPU is a serial data transfer standard known as RS232C or V24. The VDU consists of two main sections. Firstly, there is a keyboard laid out with alphanumeric keys like a standard typewriter. When a key is pressed by the operator a serial data code representing that key is transferred from the VDU to the CPU. Secondly, there is a display screen which will display alphanumeric characters representing any serial data codes sent by the CPU to the VDU.

SUMMARY OF THE INVENTION According to one aspect of the invention, in a microcomputer system which includes a visual display unit (VDU) and a central processing unit (CPU), one of which units includes a keyboard which has alphanumeric keys and a "control" key, the invention proposes the provision of an add-on device which comprises a housing, a plurality of additional keys exposed on a surface of the housing, respective electrical switches within the housing, one operatively linked to each of said additional keys, an input connection socket and an output connection socket on the housing, a first data link between one of said sockets and the VDU and a second data link between the other of said sockets and the CPU, and a programmable semiconductor device within the housing connected to said swithces and said sockets, which semiconductor device is adapted to leave the transfer of data between said units through the said links unaffected but to feed a different sequence of data characters to said output socket for each additional-key actuated on the device, at least one of said sequences corresponding to the sequence generated by said keyboard when the "control" key and at least one alphanumeric key thereon are pressed.

The proposed add-on device is a self-contained housing with an exposed surface (normally an angled top panel) on which there is an array of electrical switch-operating keys. On the housing (e.g. on the rear panel) there is a mains power connection cable, an input connection socket, an output connection socket, parameter setting switches, a mains power switch and a fuse holder.

The add-on device is connected into a microcomputer system by unplugging the serial data connecting cable between the VDU and the CPU, at the CPU and plugging it into the input connection socket of the add-on device. A cable wired to the same standard is then plugged into the output connection socket of the add-on device and into the now-vacant socket on the CPU.

When the add-on device is disconnected from the mains power source or switched off, data transfer between the VDU and the CPU is unaffected. When the add-on device is connected to the mains power and switched on there is still no affect on the data transfer from the VDU and CPU, if none of the additional keys on the add-on device is pressed. Pressing a single additional key on the add-on device causes the add-on device to send data to the CPU as if a sequence of keys has been typed on the VDU keyboard. The sequence may be any length and may contain any of the data codes, control or otherwise, allowed by the transfer standard. Thus a complex sequence of control codes can be generated from a single press of an additional key on the add-on device.

Internally the add-on device contains a programmable semiconductor devices which decodes which additional key thereon has been pressed and translates this into a sequence of data characters which are transmitted to the CPU. By reprogramming the internal semiconductor device, the add-on device may be used in any application requiring the addition of function keys to a standard VDU.

A preferred version of an add-on device according to the invention is one designed and built for use with a particular word processing programme.

.To operate a general purpose microcomputer as a word processor, requires that a specific computer programme be executed by the CPU.

There are many such programmes available, the most popular however is one sold by Micropro under the trade name "WORDSTAR".

All word processing programmes require to be given instructions as to what actions are required, for example when a word should be inserted or deleted from the text. Dedicated word processing microcomputer systems achieve this by having extended keyboards with extra keys specifically for these functions. "WORDSTAR" and similar programmes designed for use with general purpose alphanumeric keyboards on VDUs avoid the necessity for extra keys by recognising control codes as representing functions. Control codes are generated on such a standard keyboard by pressing one key marked "CONTROL" while simultaneously pressing one of the standard alphanumeric keys. This has the effect of slightly modifying the serial data sent to the CPU. It is analogous to the SHIFT key modifying the case of a letter.Unfortunately this does not provide enough separate functions, therefore sequences of two or more control codes are used for each function. For example to cause a line of text to be centred on the page, control-O then control-C must be typed.

The typist using the microcomputer system with a word processor programme therefore has to remember which sequence of control codes represent each function. This is inconvenient, particularly for typists not using the word processor programme regularly.

According to a further aspect of the invention an add-on device for a microcomputer system comprises a housing, a multikey keyboard exposed on the housing, a microcomputer device within the housing, means to link each separate key of the keyboard to the microcomputer device whereby depression of any key of at least some of the keys generates a unique sequence of standard codes, the lengths of the sequence of codes generated being different for at least two different key depressions.

Suitably there are 56 keys in the keyboard which automatically generate the more frequently required editing commands for a word-processing package in the ASCII code.

Since these editing commands normally require the depression of two keys simultaneously, a device in accordance with the invention can include a delay between each character sequence of codes which forms a component part of a full key-generated sequence - so that it more closely simulates the performance of a human operator having to generate the codes for the full sequence with a plurality of key depressions. A delay of the order of one tenth of a second has been found to be suitable.

BRIEF DESCRIPTION OF DRAWINGS One embodiment of add-on device in accordance with the invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic block diagram of the add-on device, Figure 2 shows the block diagram of Figure 1 in somewhat more detail, Figure 3 shows the complete arrangement of add-on device, CPU and VDU, and Figure 4 shows a plan of the keyboard of the add-on device.

DESCRIPTION OF PREFERRED EMBODIMENT The device shown in Figure 1 comprises a housing 1 supporting a keyboard 2, an input socket 3 and an output socket 4. Within the housing is a microcomputer device 5 and an ORgate 6.

Figure 2 shows the add-on device of Figure 1 in slightly more detail. The device generates asynchronous characters to the EIA RS232C specification which defines the voltage levels etc.

on the connecting wires and also which pin numbers on the sockets 3 and 4 are used for each function in the communications protocol. Each character generated by the device consists of 1 start bit, 8 data bits and 2 stop bits. Of the 8 data bits the 7 least significant are coded to the ASCII character coding standard. The individual keys 7 (see Figure 4) of the keyboard 2 act upon a different one of fifty-six swtiches 2b formed at the intersections of eight row wires (A-H) and seven column wires (1-0) connected to the microcomputer device 5 (e.g. an 8748-8 microprocessor).A crystal 10 controls the sequencing rate of the device 5, and a switch bank 11 permits a chosen number of resistors R, to be shorted out thereby selecting the rate at which the bits of each character are sent in "bits" per second" (baud) from the device to the CPU. In the add-on device described, the swithces in the bank 11 permit the baud rate to be 300, 600, 1200, #4OO, 4800, 9600, 19200 or 38400. A further switch 12 is provided to permit the transmitted code either to have its most significant bit zero or to ensure even parity of the 8 bits transmitted.

The code generated by the microcomputer device 5 is sent to the OR-gate 6 (constituted by two diodes 6a, 6b), and thus to the output socket 4 via a second part 13a of a voltage-level converting circuit 13a, 13b. This circuit 13a. 13b is required to adapt the 12 volt system used on the data link 15 between the VDU and the CPU to the 5 volt system used for the device 5.

A relay 14 connects the circuit 13a, 13b between the sockets 3 and 4 when the add-on device is in use but isolates the circuitry in the housing 1 when the add-on device is not connected to the mains (i.e. when the coil of the relay 14 is not energised). When the relay 14 is energised, any character codes generated at the VDU pass through the OR-gate 6 via both parts 1 3a, 1 3b of the voltage-adapting circuit and are thus forwarded without modification to the CPU.

A stabilised power supply (not shown) of conventional design is also included in the housing 1 and provides + 12 volt supplies and a + 5 volt supply.

The keyboard 2 can vary (depending on the application for the add-on device) but that shown in Figure 4 has been designed for use with the "WORDSTAR" word processing programme. It provides an array of 56 keys. Each key represents a single command in the word processing programme. The array of keys 7 is logically laid out so that related functions are in related positions. To further aid the typist, each key 7 is clearly labelled with its designated function and keys belonging to related functions are in different colours (not shown in Figure 4). The advantages of dedicated function keys are therefore acquired without any modification to the existing components in the microcomputer system or to the word processing programme.

The parameter switches 11, 12 which allow the add-on device to be selected for operation at different data transfer rates and also to select if parity bits should be added to the serial data stream can be provided on the back panel of the housing 1.

Figure 1 also shows (dotted) a modified circuit arrangement which gives a greater user flexibility.

Unit 9 is a non-volatile memory chip (e.g. an X 2804 A) which permits the user to programme the output sequence resulting from each key depression and thus allows the add-on device to be used for other applications than a specialist keyboard for a word-processing package. Unit 8 is a mode switch having three or more positions. In the first position the device behaves as the basic version of the device, i.e. each key press produces a fixed code sequence defined in the programme of the microcomputer device 5.

In the second position of the mode switch the device enters a programme mode in which sequences of key presses of the keys 7 are interpreted by the microcomputer device 5 as being the definitions of each of the sequences that are required to be generated from subsequent key presses. The sequences so defined are stored by the microcomputer device 5 in the non-volatile memory 9. In this mode, a special sheet of key designations is desirably provided to lay over the keys 7, to define the meaning of each key during the programme mode.

In the third and subsequent positions of the mode switch, the device will output, for each key press, one of the sequences of codes stored in the non-volatile memory. The exact sequence output will depend on the position of the mode switch, therefore one of two or more sets of predefined code sequence definitions can rapidly be selected.

Blank key designation sheets are provided, that can easily be marked with the key designations defined in the programme mode.

The switch 11 can be redefined as the mode switch 8, and the baud rate can be set using the keyboard 2, as part of the programming mode.

Claims (13)

1. An add-on device for a microcomputer system comprising a housing, a multikey keyboard exposed on the housing, a microcomputer device within the housing, means to link each separate key of the keyboard to the microcomputer device whereby depression of any key of at least some of the keys generates a unique sequence of standard codes, the lengths of the sequence of codes generated being different for at least two different key depressions.

2. An add-on device as claimed in claim 1, in which the keyboard is located on an angled top panel of the housing.

3. An add-on device as claimed in claim 1 or claim 2, in which there are 56 keys in the keyboard.

4. An add-on device as claimed in any preceding claim, in which the separate keys automatically generate the more frequently required editing commands for a word-processing package in the ASCII code.

5. An add-on device as claimed in claim 4, in which means is provided to introduce a delay between each character sequence of codes which forms a component part of a full key-generated sequence.

6. An add-on device as claimed in any preceding claim, in which the sequence of standard codes generated as a consequence of any respective key depression can be modified with the aid of a non-volatile memory means.

7. An add-on device as claimed in claim 6, in which a mode switch is included to permit a) the memory means to be programmed by user depressions of the keys and b) the preprogrammed sequences to be recalled.

8. A microcomputer system which includes a visual display unit (VDU) and a central processing unit (CPU), one of which units includes a keyboard which has alphanumeric keys and a "control" key, and an add-on device which comprises, a housing, a plurality of additional keys exposed on a surface of the housing, respective electrical switches within the housing, one operatively linked to each of said additional keys, an input connection socket and an output connection socket on the housing, a first data link between one of said sockets and the VDU and a second data link between the other of said sockets and the CPU, and a programmable semiconductor device within the housing connected to said switches and said sockets, which semiconductor device is adapted to leave the transfer of data between said units through the said first and second data links unaffected, but to feed a different sequence of data characters to said output socket for each additional key actuated on the device, at least one of said sequences corresponding to the sequence generated by said keyboard when the "control" key and at least one alphanumeric key thereon are pressed.

9. A system as claimed in claim 8, in which the keyboard is located on angled top panel of the housing, the housing including a switch means actuable to connect the two connection sockets together when the semiconductor device is not energised to generate data characters.

10. A system as claimed in claim 8 or claim 9, in which the semiconductor device is programmed to generate asynchronous characters to the EIA RS232C specification.

11. An add-on device for a microcomputer system substantially as hereinbefore described in Figure 1 but without integers 9, 11 and 12.

12. An add-on device as claimed in claim 11 having a keyboard substantially as shown in Figure 4.

13. A microcomputer system substantially as hereinbefore described with reference to the accompanying drawings.