JPH07101877B2 - Terminal device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] The present invention relates to a terminal device having a function of receiving data from an external control device or through-passing to the next stage, and for the purpose of efficiently and inexpensively receiving data. In a system in which a plurality of terminal devices that communicate with each other are connected by sharing a common transmission line, a receiving unit that receives data from the control device for each of the plurality of terminal devices, and the receiving unit. And a holding circuit for holding the polling signal received by the receiving means, and whether the data from the control device received by the receiving means is to be passed through to the predetermined terminal device of the next stage and thereafter, and only when the own data is transmitted. The output is set to the mark state, and after the data transmission is completed, the polling signal from the holding circuit is output to the predetermined terminal device at the next stage and thereafter, and the first selection circuit itself transmits to the control device. A data transmission circuit that generates data and transmission data from itself to the control device or from the predetermined terminal device in the next stage or later are selected, and the data generated by the data transmission circuit is selected only when the data is transmitted by itself. And a second selection circuit for outputting to the control device.

[Industrial application field]

The present invention relates to a terminal device, and more particularly to a terminal device having a function of receiving data from an external control device or through-passing to the next stage.

[Conventional technology]

In a system in which multiple terminal devices share a common transmission line to send and receive information, a control method to avoid data collision on the transmission line is required, and the token passing method is well known as this control method. Has been.

In this token passing system, a plurality of terminal devices are connected to a ring-shaped transmission path, and one special frame called a token (identifier) is regenerated and relayed by each terminal device and circulates along the ring. Since the terminal device having the transmission data is configured to have the transmission right only when the token is received by itself, the data collision can be avoided.

[Problems to be Solved by the Invention]

However, in this token passing method, each terminal device has to transmit the received data to the terminal device in the next stage while detecting the token, and the cost is high due to complicated control performed by hardware. There is.

The present invention has been made in view of the above points, and an object of the present invention is to provide a terminal device that can efficiently perform data transmission at low cost.

[Means for Solving the Problems]

FIG. 1 shows the principle configuration of the present invention. In the figure, reference numeral 21 is a receiving means, which receives data from the control device. A holding circuit 22 holds the polling signal received by the receiving means 21. A first selection circuit 23 selects whether to pass through the data from the control device to the predetermined terminal device of the next stage and thereafter, sets the output to the mark state only when transmitting its own data, and holds the circuit after the data transmission is completed. The polling signal from 22 is output to the predetermined terminal device after the next stage.

A data transmission circuit 24 generates data to be transmitted to the control device. 25 is a second selection circuit, usually a control device
Data to be transmitted to itself or from a predetermined terminal device after the next stage to 10 is selected, and data generated in the data transmission circuit 24 is selected only when the data is transmitted by itself and output to the control device.

[Action]

Terminal apparatus according to the present invention are each of the terminal devices 20 ₁ to 20 _n in the system as shown in Figure 2. In the figure, 10 is a control device, which transmits a polling signal and the like, and the terminal devices 20 _{1 to} 20 _n
Communicate with. The terminal devices 20 _{1 to} 20 _n are connected by sharing a common transmission line.

Each of the terminal devices 20 _{1 to} 20 _n has a principle configuration as shown in FIG. 1, and normally, the data sent from the control device is received by the receiving means 21 and passed through the first selecting circuit 23. And transmits the data sent from the terminal device of the next stage to the control device 10 through the second selection circuit 25. The final stage (farthest from the control device 10)
In the terminal device 20 _n of the second output terminal of the first selection circuit 23,
Is connected to the input terminal of the selection circuit 25.

Therefore, normally, the data sent by the control device 10 are simultaneously received by the terminal devices 20 _{1 to} 20 _n in the loop, and this data is returned to the control device 10 via all the terminal devices 20 _{1 to} 20 _n. Come on.

Here, since the terminal device with the data transmission request sets the output of the first selection circuit 23 to the mark state, the polling signal is not transmitted to the terminal devices after the terminal device with the data transmission request, and the data transmission is not performed. It is held by the holding circuit 22 in the requested terminal device.

The terminal device with a data transmission request is then sent to the transmission circuit 24
The data generated by
To the holding circuit via the first selection circuit 23.
The polling signal held in 22 is transmitted.

Therefore, in the present invention, the polling signal is transmitted to a plurality of terminal devices 20.
Out of _{1 to} 20 _n, the terminal device that does not request data transmission is through-passed, and the terminal device with the data transmission request closest to the control device 10 is received, and the transmission of polling signals to the next terminal device is blocked, and data transmission is performed. Data communication with the control device 10 can be performed with a simple configuration of later releasing the mark state and sending a polling signal.

〔Example〕

FIG. 3 shows a block diagram of an embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 3, reference numeral 30 denotes a control circuit, which controls the entire terminal device. The receiver (RV) 31 and the receiving circuit 32 constitute the receiving means 21, and the holding circuit 33 constitutes the holding circuit 22. 34 and 37 are multiplexers (MPX), which constitute the selection circuits 23 and 25, and the transmission circuit 36 constitutes the data transmission circuit 24.

Data from the control device 10 is input to the receiver (RV) 31 directly or via another terminal device. Assuming that this terminal device has no data request, the control circuit 30
At the same time as setting X34 to the output data passing state of RV31, MPX37 is controlled to the output data passing state of receiver (RV) 38. Therefore, in this case, the data taken out from the receiver 31 is received by the receiving circuit 32, while the MPX 34 and the driver (D
V) 35 and sent to the next terminal. Also, in this case, the data from the next terminal device input to the RV38
It is transmitted to the control device (10 in FIG. 2) through the MPX37 and DV39. Therefore, when there is no data request, the terminal device passes the data from the control device 10 and sends it to the next terminal device, while the data from the next terminal device goes through and sends it to the control device 10.

Next, a case where this terminal device has a data request will be described. In this case, the control circuit 30 sets the output of the MPX 34 to the mark state (holds the predetermined logical value) and switches the MPX 37 to the output data passing state of the transmission circuit 36. As a result, although the polling signal transmitted from the control device 10 is received by the receiving circuit 32 via the RV 31, the MPX 34 blocks the transmission to the next terminal device. The polling signal received by the receiving circuit 32 is held by the holding circuit 33 connected via the bus 40 under the control of the control circuit 30.

Next, under the control of the control circuit 30, the data to be transmitted is transmitted from the transmission circuit 36 and is transmitted to the control device 10 via the MPX 37 and the DV 39, respectively. When this data transmission is completed,
The control circuit 30 switches the MPX 34 to the output signal passing state of the holding circuit 38 and switches the MPX 37 to the output signal transmitting state of the RV 38. Therefore, the polling signal held in the holding circuit 33 is sent to the next terminal device through the MPX 34 and the DV 35, respectively. After transmitting the polling signal, the control circuit 30
Return the MPX34 to the normal state of the RV31 output passing state.

Next, the operation sequence in the case where the terminal device of the present embodiment having the above configuration were respectively used to the terminal apparatus 20 ₁ to 20 _n of FIG. 2 with Figure 4. FIG. 4 shows an example in which the number n of the terminal devices 20 _{1 to} 20 _n shown in FIG. 2 is set to “3”, and the terminal device 20 ₂ has a data transmission request and the terminal devices 20 ₁ and 20 ₃
Indicates that there is no data transmission request.

The post-natal device 10 transmits a gate control (GC) signal notifying the polling timing before starting polling. The GS signal is received simultaneously in all of the terminal devices 20 ₁ to 20 _3, as shown at 41 in FIG. 4, returns to the control device 10. A terminal device that has received a GC signal and has a data transmission request
20 ₂ is the mark state output of MPX34 as shown at 42 in Figure 4.

On the other hand, the control device 10 that has received the GC signal transmits a polling signal after a predetermined time has elapsed from the time when the GC signal was received. This polling signal passes through the terminal device 20 ₁ as shown by 43 in FIG. 4, is received by the terminal device 20 ₂ , and is not transmitted to the terminal device 20 ₃ . When the terminal device 20 ₂ receives the polling signal,
As shown at 44 in FIG. 4, the holding circuit 33 holds the polling signal, and the transmitting circuit 36 transmits data through the MPX 37. This transmission data is sent to the terminal device as indicated by 45 in FIG.
It is received by the controller 10 through the 20 _1.

When the terminal device 20 ₂ ends the data transmission, as shown at 46 in FIG. 4, MPX34 and D than the holding circuit 33 a polling signal
It is sent to the terminal device 20 ₃ via V35. This transmission polling signal is returned by the terminal device 20 _{3 as} shown at 47 in FIG. 4, further passes through the terminal devices 20 ₂ and 20 _{1, respectively,} and is transmitted to the control device 10 where it is received. The control device 10 is configured not to generate the next polling signal until the transmitted polling signal is folded back and received, and the GC signal of the timing notification of the next polling signal transmission is not received until the polling signal is received. Is ready to be sent.

In the case where the data transmission request issued for the terminal is two or more of 20 ₁ to 20 _3, the above operation sequentially from the nearest terminal to the controller of the data communication request There the terminals are repeated.

In this way, according to this embodiment, data transmission between a plurality of terminal devices and the control device 10 can be sequentially performed without data collision.

〔The invention's effect〕

As described above, according to the present invention, a terminal device with a data transmission request has a simple configuration of blocking the passage of a polling signal to the next terminal device, releasing the mark state after data transmission, and sending a polling signal. Since data can be transmitted between the terminal and the terminal device, even if there are a plurality of terminal devices, the data transmission can be performed efficiently and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing a system to which the present invention can be applied, FIG. 3 is a block diagram showing an embodiment of the present invention, and FIG. 4 is a view showing an embodiment of the present invention. It is an operation sequence diagram of a system including a terminal device. In the figure, 10 is a control device, 20 _{1 to} 20 _n are terminal devices, 21 is a receiving means, 22 is a holding circuit, 23 is a first selection circuit, 24 is a data transmission circuit, and 25 is a second selection circuit. .

Claims (1)

[Claims] 1. A system in which a plurality of terminal devices (20 _{1 to} 20 _n ) communicating with a control device (10) are connected by sharing a common transmission line, the plurality of terminal devices (20). _{1 to} 20 _n ), receiving means (21) for receiving data from the control device (10), holding circuit (22) for holding the polling signal received by the receiving means (21), It is selected whether the data from the control device (10) received by the receiving means (21) is to be passed through to the predetermined terminal device of the next stage and thereafter, and the output is set to the mark state only when the data is transmitted by itself. After completion of data transmission, a first selection circuit (23) for outputting a polling signal from the holding circuit (22) to the predetermined terminal device at the next stage and thereafter, and data to be transmitted to the control device (10) by itself. And a data transmission circuit (24) for generating Alternatively, the transmission data from the predetermined terminal device of the next stage and thereafter is selected, and the data generated in the data transmission circuit (24) is selected only when the data is transmitted by itself and is output to the control device (10). Selection circuit (2
5) and a terminal device characterized by comprising the following.