GB2234104A

GB2234104A - Computer workstation network

Info

Publication number: GB2234104A
Application number: GB8915698A
Authority: GB
Inventors: Alan Bradford
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-07-08
Filing date: 1989-07-08
Publication date: 1991-01-23
Anticipated expiration: 2009-07-08
Also published as: GB8915698D0; GB2234104B

Abstract

A plurality of computer workstations (2) are linked by a common data bus to a master console (6). The master console (6) is operable to tap into a selected work station and to monitor secretly the video signals being produced by the work station (2). The master console (6) is also operable to use a master work station (8) to transmit video signals to one or more selected work stations (2) for viewing on the screen in place of any locally generated video signals. <IMAGE>

Description

COMPUTER WORKSTATION NETWORKS The present invention relates to computer workstation networks.

Teaching and industrial organisations employ networks of computer workstations. Each workstation may comprise a personal computer (P.C.) at which selected individuals perform selected tasks.

Instead each P.C. may be programmed to perform an industrial process.

Such workstations are often linked or networked to enable communication between selected P.C. '5.

Such networking of workstations is often limited in scope.

It is an object to provide an improved computer work station network.

According to the present invention there is provided a computer workstation network comprising a plurality of separate computer workstations, a master station and a data bus connected to said master station, each said work station being linked to said bus and incorporating logic means which can be selectively addressed by said master station in a monitoring mode, to cause video data generated by selected work station to be transmitted to along said bus to the master station, thereby to enable the master station to monitor the video signals generated by the selected work station, and which logic means can also be addressed by said master station in a display mode to cause video data generated by the master station and transmitted along said bus to enter said computer work station for display on a video screen therein.

A computer workstation network will now be described, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a block diagram of the network; Figure 2 is a flow chart for a work station as connected to a data bus; Figure 3 is a circuit diagram of the work station of Figure 2; Figure 4 is a plan of the keyboard of a master console; Figure 5 is a flow chart of the master console of Figure 4; and Figure 6 is a circuit diagram of the master console of Figure 5.

Figure 1 shows an array of fifteen P.C.

workstations 2 linked by a common bus 4 to a master console 6 having an integral VDU 6A, and an associated master work to station 8. The master console 6 and master work station 8 together form a master station.

In operation each of the fifteeen P.C workstations is manned by an indepedent operator who is operating the P.C. on the basis of individual instructions. The master work station 8 may also be manned by an operator when not required for use in a transmit mode by the master console 6.

Using the master console 6 a supervisor can tap into selected work station and cause the video signals (in digital form) being generated, to be transmitted along the bus 4 to the VDU 6a of the master console 6 where they can be viewed on a screen. This can be done in total secrecy without the operator of the work station 2 being aware that he is being monitored.

The master console 6 also has the facility to select one or more of the work stations 2 and to interrupt the locally generated video signals and instead cause a video signal generated by the master work station 8 to be displayed on the screens of the selected work station or stations.

Since the master console 6 can selectively switch each work station 2 between transmit and receive modes it will be appreciated that two way communication between the master console 6 (including the master workstation 8) and each workstation 2 can take place.

Figure 2 is a flow chart showing the flow of data between the workstation and the common bus 4.

The data bus 4 has four basic channels; a data channel 10 for transmitting digital video signals between the master work station 8 and work station 2 and between each work station 2 and the master console 5, a transmit address channel 12 for actuating a selected workstation into a reception mode, a receive address channel 14 for enabling a selected workstation to operate in a sending mode, and a logic channel 16 (consisting of a receive and transmit logic sub channels (16A and 163) for conditioning the logic circuitry of the work station, selected by commands transmitted along one of the two address channels 12 and 14.

Each work station has a VDU (Visual Display Unit) connector 20 which feeds a VDU (not shown).

The output of a keyboard (not shown) of the VDU feeds a graphics controller card of the VDU, and the output connector 24 of the graphics controller card is coupled to the connector 20 through a buffer 26. The connector 20 is also connected to the channel 10 via a bidirectional buffer 22.

In the channel 10 just downstream (with respect to the master console 6) of the point at which the connector 20 is connected to the channel, is a bidirectional buffer 30.

Each buffer 22 and 30 can be switched by logic circuitry into one of three modes namely a first mode in which signals are allowed to pass in one direction and are amplified at the same time, a second mode in which signals are allowed to pass in the opposite direction and are amplified at the same time and a third mode in which the passage of all signals is blocked.

Each buffer 26, 22 and 30 is controlled by a respective logic element 32, 32 and 36.

Each workstation has a transmit decoder 38 which is coupled directly to the transmit address channel 12. The decoder 38 feeds an address select switch 40 which generates an output only when the received address matches the unique address programmed into the switch 40.

A logic element 42 coupled to the transmit logic channel 163, is responsive to an enable signal to enable the transmit decoder 38. The element 42 is also responsive to another logic element 50 to latch the decoder 38 in an enabled state.

Each work station has a receive decoder 44 which is coupled directly to the receive address channel 14. The decoder 44 feeds an address select switch 44 which generates an ouput only when the received address matches the unique address programmed into the switch 46. A logic element 48 coupled to the receive logic channel 16A is responsive to an enable signal to enable the receive decoder 44.

Logic elements 50 and 52 coupled to the outputs of the respective address units 40 and 46 respond to received signals to control the three logic elements 32, 34 and 36.

A buffer amplifier 60 is provided in the receive address channel 14 and receive logic channel 16A just downstream of the coupling to the workstation, and a buffer amplifier 62 is also provided in the transmit address channel 12 and the transmit logic channel 16B just downstream of the coupling to the work station.

In operation if a selected work station is required by the master console to adopt a send mode so that the operator of the master console can monitor what is appearing on the screen of the selected work station, then the address of the selected work station is transmitted along the receive address channel 14 and simultaneously a logic enabling signal is transmitted along the transmit logic channel 16A.

The logic unit 44 of all the workstations will respond and enable the transmit decoder 44 in each station. However, only the address selection switch 46 having an address corresponding to that transmitted along the receive address channel 12 will respond with an output. The logic element 52 responds to operate the logic elements 36 and 34.

The logic element 36 when operated switches the bidirectional element from a normally open into a blocking state so that no data can be transmitted to any work station downstream of the selected work station. The logic element 34 when operated changes the bidirectional buffer 22 from a normally blocking state into an open state. Thus data generated at the output terminal 24 of the keyboard passes through the normally open buffer 26 and is fed to the VDU and simultaneously through the now open buffer 22 to be transmitted along the data channel 10 to the master console 6.

Similarly if a selected work station is required by the master console 6 to adopt a reception mode so that the operator of the console can transmit data to appear on the screen of a selected work station, an enable signal is transmitted to the transmit logic channel 16B and an address signal corresponding to the address of the selected work station is transmitted along the receive address channel 12.

Each workstation will decode the address with its transmit decoder 38 following enablement by the logic element 42 responding to the transmit logic channel 163 but only the workstation with the same unique address as the transmitted address will respond and cause the logic element 50 on the one hand to latch the logic element 42 and on the other hand to act on the logic elements 36 ,34 and 32. The logic element 32 will cause the normally open buffer switch 26 to adopt a blocking mode, will cause the normally blocked buffer switch 22 to adopt an open mode and will not effect the normally open bidirectional switch 30. Thus any data fed to the data channel 10 from the master work station 8 will pass through the buffer switch 22 and appear on the screen of the VDU (not shown). Locally generated video signals will be blocked by the buffer 26.

The circuit diagram of the described system is more clearly shown in Figure 3. As can be seen two integrated circuits 60 and 62 are respectively connected to channel pairs 14,16A; and 12, 163. When the work station is operating normally (without being actively engaged with the master console or with the master workstation) both integrated circuits 60-and 62 are disabled.

Each integrated circuit is coupled to two eight way DIP switches which are programmed to respond only when the correct address appears on a corresponding data channel.

The remainder of the circuit will be apparent to those skilled in the art.

The master work station 8 differs from the work station 2 in that the elements 38, 40, 42 and 50 are omitted and an additional logic element (not shown) is included to cause the buffer 22 to operate in its first mode (ie to pass signals from the connector 20 to the bus 10) when a signal appears in the transmit select logic bus 163.

The master console 6 is provided with a keyboard 70 (see Fig 4) to enable desired communication to take place.

The keyboard has sixteen receive keys 72 each with an associated pilot light 74, a receive key 76 and a NORMAL key 77.

Also provided are sixteen transmit keys 78, each with an associated pilot light 80, a transmit key 82 and a clear key 84.

The flow chart associated with the keyboard 70 is more clearly shown in Figure 5.

Operation of any of the keys 76 (Receive), 77 (Normal) and 82 (Transmit) will be decoded into digital form by a key encoder 86. A logic circuit 88 responds to the output of the key encoder 86 by generating or discontinuing a signal on a corresponding one of the two logic channels 16A and 16B. Where the Transmit key 82 has been operated, the logic circuit 88 also causes a logic element 90 to enable a key encoder 92 coupled to the keys 78.

Where the Receive key has been operated the logic circuit also causes a logic element 94 to enable a key encoder 96 coupled to the keys 72.

If with the Transmit key 82 depressed, a key 78 is depressed, then the encoder 92 will produce a digital address signal corresponding to the key depressed and cause the signal to be transmitted to the transmit address channel 14.

If with the receive key 76 depressed a selected key 72 is depressed, the encoder 96 will respond to generate the receive address of the corresponding work station on the receive address channel 14.

A decoder 100 is connected to the output of the encoder 96 to energise a corresponding pilot lamp 74 through a buffer amplifer 102.

A multiplexer 104 is connected to the output of the encoder 92 to energise one or more of the corresponding pilot lamps 80 via a latch 106 and a buffer amplifier 108. The clear button 84 is operable to release the latch 106 and so extinguish the pilot lamps 80.

The multiplexer 104 is provided in the event that more than one key 78 is operated, when the operator of the master console requires to transmit data to more than one work station. A special key 78A is provided to enable the addresses of all work stations to be transmitted simultaneously along the transmit address channel 12.

In the case of the receive keys 72 since only one work station can be monitored at any one time, the key encoder 96 is so organised that only one address is transmitted on the receive address channel 14.

The system has been described with sixteen work stations and one master console. However, it will be appreciated that an expansion unit can be coupled to the master console to allow the master console to control another sixteen work stations all coupled to their own data bus. In this way the master console can monitor any one of the thirty two work stations and can transmit data to, upto thirty two work stations simultaneously. This can be expanded further in a similar manner to add an indefinite number of multiples of sixteen work stations.

Figure 6 shows a circuit diagram of the master console.

Claims

1. A computer work station network comprising a plurality of separate computer workstations, a master station and a data bus connected to said master station, each said workstation being linked to said bus and incorporating logic means which can be selectively addressed by said master station in a monitoring mode, to cause video data generated by the selected work station to be transmitted along said bus to the master station thereby to enable the master station to monitor the video signals generated by the selected work station, which logic means can also be addressed by said master station in a display mode to cause video data generated by the master station and transmitted along said bus to enter said computer workstation for display on a video screen therein.

2. A computer work station network according to Claim 1 wherein said data bus includes a logic channel for supplying the logic means of each work station with a command signal for conditioning the work station to transmit or receive data.

3. A computer work station network according to Claim 1 or to Claim 2 wherein said data bus includes a first address channel for transmitting address data to selectively address the transmission sections of the work stations through their logic means and a second address channel for transmitting the address data to selectively address the receiving sections of the work stations through their logic units.

4. A computer work station network according to any preceding claim wherein said data bus includes a data channel for transmitting video data to and from each station, the data channel containing for each station a bidirectional buffer switch located on the downstream side of the channel, with respect to the master control station from the connection point with that work station, the logic means of that station responding to signals in other channels of the data bus to selectively set the buffer switch in a blocking or transmission mode whereby to block or allow the transmission of data along the data bus to work stations downstream thereof.

5. A computer work station network according to any preceeding claim wherein the logic means includes transmit and receive decoders respectively coupled to transmit and receive address channels of the data bus, transmit and receive address selection switches respectively connected to receive the outputs the transmit and receive decoders and responsive to the output thereof only when the address received matches the unique address programmed therein.

6. A computer workstation network according to Claim 5 including logic units responsive to the output of said transmit address selection switch to inhibit locally generated video signals and to direct video signals transmitted along the data bus to the video display unit of the selected work station.

7. A computer workstation network according to Claim 5 including logic units responsive to the output of said receive address selection switch to tap into the locally generated video signals and supply them to the data bus for transmission to the master station.

8. A computer workstation network substantially as hereinbefore described with reference to the accompanying drawings.