JPH0689261A - Display system - Google Patents

Abstract

PURPOSE:To eliminate necessity for specially prepairing a communication program, etc., and to simplify configuration by mutually exchanging a communication end signal and executing data communication with a programable controller in order. CONSTITUTION:Plural display equipments D1, D2,...Dn are connected in parallel to a communication cable 2 extended from a link unit which is connected to the programable controller 1. By mutually exchanging the communication end signal with a communication line 7 among the display equipments D1, D2,...Dn, respective kinds of data communication between the plural display equipments D1, D2,...Dn and the programable controller 1 is executed in order. That is, data communication between the plural display equipments D1, D2,...Dn and the programable controller 1 is executed by time-division without prepairing a special communication program in the programable controller 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display system equipped with a programmable controller and a display for displaying various information under the control of the programmable controller.

[0002]

2. Description of the Related Art For example, in a machine tool or the like compatible with factory automation, a display is incorporated on the control panel surface to display an operation menu, an operating state, and an abnormal place. Such a display device includes, for example, a liquid crystal display panel and an image memory capable of storing image information.

Such a display device is connected to a programmable controller via a communication cable. Information corresponding to the contents to be displayed is given to the display from the programmable controller via the communication cable. As such a display device, a so-called programless type display device has recently been provided which allows the display device to access the memory in the programmable controller. That is, the display device reads out the contents written in the memory provided inside the programmable controller and displays based on the contents.

This programless type is connected to a programmable controller via a so-called link unit. The link unit is a communication device that acts as a mediator of data communication between the programmable controller and an external device. In a system in which a programless type display unit is connected to a programmable controller via a link unit in this way, data communication is performed exclusively in the link unit, so data exchange with each display unit is performed during the program executed by the programmable controller. You don't have to include a complicated communication program for. Therefore, there is an advantage that the work of creating the program executed by the programmable controller is significantly reduced.

[0005]

Due to the characteristics of the link unit, one display unit is connected to one link unit, so if a plurality of display units are to be associated with one programmable controller. In some cases, multiple link units are required. Therefore, if a large number of display units are connected in parallel to one programmable controller, a large number of link units are required, which causes a problem of high cost.

On the other hand, if the link unit is not used, it is necessary for the programmable controller to transmit data according to the communication procedure on the display side as described above. Therefore, in order to realize data communication with a plurality of display devices, it is necessary to prepare a complicated communication program in the programs executed by the programmable controller. Therefore, the preparation work for constructing the display system becomes complicated.

Therefore, an object of the present invention is to solve the above technical problems and to provide a display system in which a plurality of display devices can be connected to one programmable controller inexpensively and easily. .

[0008]

A display system according to claim 1 for achieving the above object is a programmable controller, a communication means for mediating data communication between the programmable controller and an external device, and this communication. A plurality of indicators connected in parallel to the means and individually performing data communication with the programmable controller;
And a communication line connecting between the plurality of display units, each display unit in response to a predetermined communication end signal is given from one display unit via the communication line, and the programmable controller And a means for transmitting a communication end signal to another display unit via the communication line after the end of the data communication.

The display system according to claim 2 is provided corresponding to each display device, and when the power supply to each display device is cut off,
It is characterized by further including signal transmitting means for transmitting the communication end signal from the one display unit to the other display unit as it is.

[0010]

According to the above construction, the plurality of display devices connected in parallel to the communication means can communicate with each other via the communication line. Then, each display receives a communication end signal from another display via the communication line, and starts data communication with the programmable controller in response to the communication end signal. When this data communication ends, the display unit gives a communication end signal to another display unit.
In this way, the plurality of display devices sequentially perform data communication with the programmable controller.

In this way, by connecting a plurality of display units in parallel to one communication means and exchanging a communication end signal between the plurality of display units, data communication between each display unit and the programmable controller is performed. It can be done without any trouble. If each display is equipped with a signal transmission means that transmits the communication end signal given via the communication line when the power is shut off to another display as it is, one of the displays will be in the power-off state. Even if there is, a communication end signal can be exchanged between the remaining displays. As a result, it is possible to favorably perform data communication between each power-on display unit and the programmable controller.

[0012]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a simplified configuration of a display system according to an embodiment of the present invention. This display system is used in, for example, a factory automation system, and a plurality of display devices D are connected to one programmable controller 1 by a communication cable 2 such as an RS422 communication cable.
1, D2, ..., Dn (n is a natural number of 2 or more.)
Are connected in parallel. More specifically, the programmable controller 1 is connected with a link unit 3 which is a communication means for mediating serial data communication with an external device, and the communication cable 2 is connected to the link unit 3.
Are connected. For this communication cable 2, so-called programless type displays D1, D2, ...
Dn are connected in parallel.

Electric power from the commercial AC power source 5 is supplied to each of the display devices D1, D2, D3, ..., Dn via a power supply line 8, and the display device D1 is turned on by turning on a switch SW1. This switch SW is powered on
When the switch 1 is in the conductive state, the switches SW2, SW3, ...
.... When SWn is turned on, the indicators D2 and D respectively
Power supply to Dn is achieved. Further, a DC voltage (for example, 24 V) for signal generation is supplied from the DC power supply 6 to each of the indicators D1, D2, ..., Dn.

The display units D1, D2, ..., Dn are connected by a communication line 7 in a ring shape. Explaining in more detail, the communication line 7 includes the indicators D1, D2, ...
.., Rn as signal transmission means provided in association with Dn are connected in series. Then, the relay units R1, R2, ...
, Rn are connected to a communication end signal input terminal T _IN and a communication end signal output terminal T _OUT , which are respectively provided in the display devices D1, D2, ..., Dn. Relay unit R
1, R2, ..., Rn are the indicators D1, D2 ,.
The connection state changes when the power of Dn is turned on / off. The details will be described later.

FIG. 2 shows an indicator Di (where i = 1, 2,
..., n. 2) is a block diagram showing the electrical configuration of FIG. The display device Di includes a liquid crystal display unit 11 that displays an image by a dot matrix method. An illumination unit 12 is provided in association with the liquid crystal display unit 11 and illuminates the liquid crystal display unit 12 from behind. The entire operation of the display device Di is controlled by a CPU (central processing unit) 13.
The CPU 13 is connected to a bus 14, and the bus 14 has a program memory 15 storing an operation program of the CPU 13, a computer memory 16 functioning as a work area of the CPU 13, and a liquid crystal display unit 1.
A memory card 17 that stores screen data and the like to be displayed on 1 and the like, a screen data memory 18 that stores the screen data, and the like are connected. Bus 14
Further, a communication control circuit 20 connected to the communication cable 2 and an input / output port 21 are connected to the.

The input / output port 21 includes an operation section 22 provided on the front surface of the display Di and the input / output terminals T _IN ,
T _OUT is connected. Furthermore, this input / output port 2
A display drive circuit 23 for driving the liquid crystal display unit 11 is connected to 1, and a display data memory 24 for storing data to be displayed is connected to the display drive circuit 23. The display drive circuit 23 creates a drive signal based on the data stored in the display data memory 24 and applies it to the liquid crystal display unit 11.

FIG. 3 is a block diagram showing a configuration related to data communication on the display Di. Each display Di
Performs data communication with the programmable controller 1 via the communication cable 2, respectively, reads out the content to be displayed from a memory (not shown) in the programmable controller 1, and displays it on the liquid crystal display unit 11. For example, when the communication cable 2 is an RS422 communication cable, this communication cable 2 is composed of four lines. Two of them are output lines L _OUT to which the data from the display device Di are transmitted, and the other two are the display line D _OUT.
The data to be captured in i is the input line L _IN derived from the link unit 3. The output line L _OUT and the input line L _IN are connected to the gate circuits 31 and 32, respectively. The gate circuit 32 corresponding to the input line L _IN can always take in the input data inside, and the gate circuit 31 corresponding to the output line L _OUT is supplied with the opening / closing control signal. Therefore, data can be sent to the output line L _OUT only for a limited period.

On the other hand, the relay unit Ri is provided with a relay coil 33 which is connected to the commercial AC power source 5 (see FIG. 1) via the switch SWi and is excited / demagnetized by turning on / off the power of the display Di. ing. That is, the relay coil 33 is excited when the switch SWi is turned on and the display Di is powered on, and the switch SWi is shut off or the power supply line is disconnected, so that the power to the display Di is not supplied. It is degaussed when cut off.

Excitation / demagnetization of the relay coil 33 switches the relay contact 34. Specifically, when the power is cut off, the input / output terminal T of the communication end signal to the relay coil 33
1 and T2 are short-circuited (indicated by a broken line in FIG. 3). Therefore, the upper display D is connected via the communication line 7.
The signal given from (i-1) is given to the lower-order display D (i + 1) as it is.

On the other hand, when the power is turned on, the relay coil 33
Is excited, and the relay contact 34 enters the state shown by the solid line in FIG. 3, that is, the signal from the input terminal T1 is output to the output terminal T3.
It is given to the communication end signal input terminal T _IN indicator Di via a signal from the communication end signal output terminal T _{OU T} is given from the input terminal T4 to the output terminal T2. FIG. 4 shows an indicator Di
3 is a timing chart for explaining a signal led to a communication end signal output terminal T _OUT . 4A shows the communication end signal, and FIG. 4B shows the data communication timing of the display Di. The display Di raises the communication end signal to a high level before opening the gate circuit 31 and deriving the data to the output line L _OUT of the communication cable 2. After that, data communication is performed with the programmable controller 1 via the output line L _OUT and the input line L _IN . Then, when the data communication ends, the display unit Di lowers the communication end signal to the low level.

This communication control signal is output to the output terminal T._OUTFrom
Via the relay unit Ri to the lower display D (i + 1)
Given. This display D (i + 1) has its input end
Child T _INThat the communication end signal given to
The higher display unit Di is a programmable controller
It is determined that the data communication with 1 has been completed. In addition, also
However, the power supply of the lower display D (i + 1) is cut off.
If so, the communication end signal is transmitted to the relay unit R (i + 1).
Pass it and give it to the next relay unit R (i + 2)
Will be done.

FIG. 5 is a timing chart for explaining the data communication operation between the plurality of displays D1, D2, ..., Dn and the programmable controller 1 immediately after the power is turned on. 5 (a), (b), (c), and (d) show the timings at which the displays D1, D2, D3, and Dn communicate with the programmable controller 1, respectively. At least the display D when the switch SW1 and the like are turned on.
When a plurality of display devices including 1 are turned on, for example, at time t0, the respective display devices D1, D2, ..., Dn become operable.

Then, in the period from time t1, first, the uppermost display D1 performs data communication with the programmable controller 1. When the data communication on the display device D1 ends, the communication end signal falls, and in response to this, the display device D2 performs data communication with the programmable controller 1 in the period from time t2. Further, when the data communication on the display D2 is completed, the display D2
Lowers the communication end signal derived to its output terminal T _OUT . In response to this, the display device D3 starts data communication in the period from the time t3. When the data communication on the display device Dn ends, in response to this,
During the period from time t (n + 1), the display D1 again performs data communication with the programmable controller 1.

Such a communication operation is, so to speak, a communication in which the uppermost display device D1 is a main station and the lower display devices D2 to Dn are subordinate stations subordinate to the display device D1. That is, immediately after the power is turned on, the display device D1 always performs the data communication first, so that the subsequent data communication can be performed without any trouble. Moreover, in the configuration of FIG. 1, since the display D1 is always powered on, the data communication can be surely started.

As described above, according to the display system of this embodiment, the communication cable 2 extending from the link unit 3 connected to the programmable controller 1 is provided with a plurality of indicators D1, D2, ..., Dn. Are connected in parallel.
, Dn are transmitted and received between the display devices D1, D2, ..., Dn via the communication line 7, and the plurality of display devices D1, D2 ,. Each data communication with 1 will be performed in order. That is, data communication between the plurality of display devices D1, D2, ..., Dn and the programmable controller 1 is performed in a time-division manner even if a program for communication is not prepared in the programmable controller 1, Two
A situation in which one or more indicators Di simultaneously send data to the communication cable 2 does not occur.

As described above, according to this embodiment, a plurality of indicators D1, D2, ...
By connecting Dn in parallel, individual data communication between the programmable controller 1 and the plurality of displays D1, D2, ..., Dn can be performed without any trouble. Therefore, the number of link units can be reduced by (n-1) units as compared with the conventional case. Thus, with a low-cost configuration, a plurality of display devices D1,
D2, ..., Dn can be connected.

Moreover, since it is not necessary to prepare a special program for communication in the programmable controller 1, complicated preparation work is not required when constructing the display system. The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments.

For example, as a method of starting data communication immediately after power-on, there are some methods other than the method of providing the main station as described above. One of them is each display Di
This is a method in which the standby time from power-on to communication start is different for each. More specifically, immediately after the power is turned on, when data communication is sequentially performed from the first display unit D1, the time t required for the i-th display unit Di to start communication t
(I) is stored in the internal memory of each display unit Di or set by a switch. However, t (1) <t (2) <t (3) <... <t (n). Then, after the power is turned on, the upper display D (i-1)
Therefore, when the time T when the communication end signal is not given becomes T ≧ t (i), the i-th display unit Di starts data communication. As a result, the upper display devices D1 to D (i-
Even when the power of 1) is not turned on, the first data communication between the programmable controller 1 and the display unit group can be performed.

In this case, since it is not necessary to provide a main station, the power switch SW corresponding to the display D1 is used.
1 may be interposed in a line 9 drawn from the power supply line 8 to the display D1. In addition, a random number value R (t) is generated for each display unit Di based on the time t, and the time T during which the communication end signal is not given from the upper display unit D (i-1) after the power is turned on, When T ≧ R (t), the display Di may start communication. However, the random number value R (t) needs to be generated differently for each display device Di.

In the above two methods, there is a possibility that two or more display devices simultaneously send data to the communication cable 2 at the beginning of communication. In order to prevent this problem, the display unit that has transmitted the data has its own standby time based on the absence of a response signal for data reception from the programmable controller 1 or an error response from the programmable controller 1. t (i), R
Data may be transmitted again after the elapse of (t).

FIG. 6 shows another example of the communication end signal for transmitting the end of communication to the lower display. In this example, a pulsed signal is output in response to the end of data communication. The lower-level display device starts communication with the programmable controller 1 in response to the pulse signal being given to the communication end signal input terminal T _IN .

Further, FIG. 7 shows another example of the connection form with the communication cable 2. In this example, an RS485 communication cable is used as the communication cable 2. That is, in this modification, the communication cable 2 is composed of two lines L that also serve as input / output lines. An input gate 41 and an output gate 42 are connected to the input / output line L.
Are connected and selectively opened by the switching control signal.

Further, in FIG. 8, a plurality of indicators D1 and D are shown.
2, ..., Dn show other connection modes for mutual communication. In this modified example, each display unit Di has a pair of input terminals x1 and x2 and output terminals y1 and y2. The output terminal y1 is connected to the input terminal x1 of the lower display D (i + 1) via the communication line 7A, and the output terminal y2 of the lower display D (i + 1) is connected to the communication line 7B. It is connected to the input terminal x2 of the display unit Di. However, in the display device D1, the input terminal x1 and the output terminal y2 are connected, and in the display device Dn, the input terminal x2 and the output terminal y1 are connected.

In such a connection mode, the signals indicating the end of communication are D2 → D3 → ...
D (n-1) → D (n-2) →
・ ・ ・ ・ → D3 → D2 → D1 With such a configuration as well, the data communication between the plurality of display devices Di and the programmable controller 1 can be performed in order, so that the data communication between the programmable controller 1 and the plurality of display devices Di can be favorably performed. .

Further, in the above-mentioned embodiment, the relay unit Ri for passing the communication control signal through when the power supply of each display unit Di is cut off is provided, but the power supply of all the display units Di is always turned on. If so, this relay unit Ri is not always necessary. In addition, the relay unit R
It goes without saying that an equivalent electric circuit may be provided in the device instead of externally attaching i to the display device Di.

Further, in the above embodiment, each display Di is
Although the power switch SWi is provided for each display unit, it is not necessary to provide a switch for each display unit Di when power is supplied to all the display units Di all at once. Further, although the programless type display device has been described as an example in the above-described embodiments, the present invention can be applied to a case where the display system is configured using a display device other than the programless type display device.

Further, in the above embodiment, the link unit 3 is connected to the programmable controller 1. However, the present invention is composed of a programmable controller having a communication means corresponding to the link unit and a display. It can be easily applied to a display system. In addition, various design changes can be made without changing the gist of the present invention.

[0038]

As described above, according to the display system of the present invention, a plurality of display devices connected in parallel to the communication means exchange data with the programmable controller by exchanging communication end signals with each other. Communication is done in order. Therefore, a plurality of display devices can be associated with one communication means without preparing a communication program or the like in the programmable controller. As a result, the configuration is simplified and the display system can be constructed at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a display system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of a display device.

FIG. 3 is a block diagram showing a configuration related to data communication of each display unit.

FIG. 4 is a timing chart showing the relationship between data communication and a communication end signal.

FIG. 5 is a timing chart for explaining the operation immediately after the power is turned on.

FIG. 6 is a timing chart showing another example of a communication end signal.

FIG. 7 is a block diagram showing an example of a connection mode between a communication cable and a display.

FIG. 8 is a block diagram showing another connection mode for communication between a plurality of display devices.

[Explanation of symbols]

1 programmable controller 2 communication cable 3 link unit 5 commercial AC power supply 7 communication line D1, D2, ..., Dn indicator R1, R2, ..., Rn relay unit T _IN communication end signal input terminal T _OUT communication End signal output terminal 7A, 7B communication line

Claims (2)

[Claims] 1. A programmable controller, a communication unit for mediating data communication between the programmable controller and an external device, and a plurality of units connected in parallel to the communication unit for individually performing data communication with the programmable controller. Display unit and a communication line connecting between the plurality of display units, and each display unit responds to a predetermined communication end signal given from one display unit via the communication line. And a means for starting a data communication with the programmable controller, and a means for transmitting a communication end signal to another display device via the communication line after the end of the data communication. Display system. 2. A signal transmitting means which is provided corresponding to each display unit and which transmits the communication end signal from the one display unit to the other one display unit as it is when the power supply of each display unit is cut off. A display system, further comprising: