JP2749417B2 - Priority control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Overview] Regarding a priority control circuit for performing priority control of a transmission request signal from a data terminal device, it is possible to flexibly respond to various system needs without wasting the circuit. It is an object of the present invention to provide a priority control circuit that has a plurality of ports to which transmission request signal lines of a plurality of data terminal devices are respectively connected, and among the internal transmission request signals supplied from each transmission request signal line, A priority control circuit that selects only an internal transmission request signal of a predetermined port at a time, and outputs the selected transmission request signal as a selected transmission request signal. A selection circuit that outputs an internal transmission request signal supplied from a corresponding port as a selection transmission request signal, and a connection unit that can be connected to a pair of other ports; Receiving the selection transmission request signal output from the selection circuit of the other port supplied from the port and supplying a selection signal indicating output prohibition to the selection circuit, the output of the selection circuit and the selection request signal of the other port, And a priority circuit for supplying a logical sum signal to the other connection unit.

The present invention relates to a priority control circuit that performs priority control of a transmission request signal from a data terminal device.

A DC branching device is provided between the data terminal device and the data transmission device. The DC branching device receives at least transmission data (SD) and a transmission request signal (RS) from the data terminal device, It outputs a transmission permission signal (CS) to the terminal device, is connected to a plurality of data terminal devices, combines transmission data from the plurality of data terminal devices into one, and transmits the data to a data transmission device or a circuit. It has a function of receiving received data (RD) from a data transmission device and passing the received data to a plurality of connected data terminal devices as received data.

As the DC branching device, for the reception data, the reception data from the data transmission device may be passed to a plurality of data terminal devices connected unconditionally, but in the transmission data, the transmission data of the plurality of data terminal devices may be transmitted. To combine them, only transmission data from one data terminal device can be sent at a time.

In a multipoint system, which is a type of data transmission system, data is normally transmitted from one data terminal device to a host by a procedure between the host and the data terminal. There is a case where the transmission request signals of a plurality of data terminal devices are simultaneously turned on due to the control of the transmission request signal of the terminal device.

When such a state occurs, in order to prevent transmission data from a plurality of ports from collapsing and destroying the transmission data, only one data terminal device is required for transmission requests from a plurality of data terminal devices. Has the function of passing the transmission data from the data terminal device that has permitted the transmission to the data transmission device at the same time as permitting the transmission to only the data transmission device. A transmission request signal priority control circuit for returning the transmission permission signal to only one data terminal device in accordance with the priority order is required.

[Prior Art] As a conventional priority control circuit for performing priority control of a transmission request signal, there is, for example, one shown in FIG.

The priority control circuit shown in FIG. 3 receives a transmission request signal RS and a control signal E from a data terminal device (not shown) and, depending on the state of the control signal E, determines whether the state of the transmission request signal RS from the data terminal device is OFF or not. Output any one of the states
The outputs of the fifth selection circuits 1 to 5 and the selection circuits 1 to 5 other than the own port are input, and the result of ORing them is output. And first to fifth OR circuits 6 to 10 which are input as control signals E of five selection circuits 1 to 5.

Now, when the transmission request signal RS is input to the port 3 from the data terminal device, the third OR circuit 8 is supplied to the third selection circuit 3.
When the control signal E is not input from the
Is sent to the port 3 internal circuit as it is,
The first, second, fourth, and fifth OR circuits 6, 7, 9, 10 are input to the
The control signal E is input to the first, second, fourth and fifth selection circuits 1, 2, 4, and 5, respectively. Therefore, in this state, even if, for example, the transmission request signal RS is input to the port 2 from the data terminal device, the second selection circuit 2 outputs the off state. Thus, the priority control of the transmission request signal RS is performed.

Outputs of the first to fifth selection circuits 1 to 5 are input to an internal circuit of the port, and after a predetermined process is performed in the internal circuit based on this signal, a transmission permission signal is sent to the data terminal device.

This embodiment is a configuration example of a priority control circuit of a DC branching device having five connected ports.

[Problems to be Solved by the Invention] However, in the conventional priority control circuit, if the number of ports of the DC branching device is different, the circuit configuration has to be changed. For this reason, the data terminal device connected to the DC branching device differs depending on the system, so that by preparing more ports than the connection ports required by the system, it has become possible to meet various needs. In addition, there is a problem that the circuit scale is wasted and that the number of ports cannot be increased later.

In some cases, a multiplexing device is provided between the data transmission device and the DC branching device depending on system needs. In this case, among the plurality of data terminal devices connected to the DC branching device, 1 to N ports are used. In this case, it is necessary to perform grouping of data terminal devices to be connected, for example, by performing DC branching at the remaining ports and performing DC branching at the remaining ports, so that the circuit configuration is further complicated, and it is not possible to respond to system needs. there were.

The present invention has been made in view of such a conventional problem, and even if a port is added, the existing circuit is substantially kept as it is, and the priority control circuit can be easily added. It is an object of the present invention to provide a priority control circuit that does not have any problem and can flexibly respond to various system needs.

[Means for Solving the Problems] FIG. 1 is an explanatory view of the principle of the present invention.

In FIG. 1, a selection circuit 21 outputs, as a selected transmission request signal, an internal transmission request signal supplied from a corresponding port to each port in response to a selection signal for permitting or prohibiting the output of the selected transmission request signal. 24 has a connection portion 22, 23 that can be connected to a pair of other ports, receives a selection transmission request signal output from a selection circuit of another port supplied from one other port, and outputs a selection signal indicating output inhibition to the selection signal. Selection circuit
And a logical sum signal of the output of the selection circuit 21 and the selection request signal of the other port.
Is a unit priority control circuit provided by the selection circuit 21 and the priority circuit 24.

[Operation] In the present invention, the unit priority control circuits of a plurality of ports connected to a plurality of data terminal devices have the same circuit configuration and are connected according to the number of required ports. There is no need to prepare more ports than the connection ports required by the system, and there is no waste in circuit scale. Further, even if the number of ports is increased, it can be easily handled.

Also, when it is necessary to group connected data terminal devices, it is possible to easily perform grouping according to the number of required ports, and to flexibly respond to system needs without complicating the circuit configuration can do.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

 FIG. 2 shows an embodiment of the present invention.

First, the configuration will be described. In FIG. 2, reference numeral 11 denotes a circuit of its own port to which the transmission request signal RS is input from the data terminal device 14, and 12 denotes a first other port to which the transmission request signal RS is input from the data terminal device 14. Is a circuit of the second other port to which the transmission request signal RS is input.

The circuit 11 of the own port includes first to third selecting circuits 15 to 17 and first to third OR circuits 18 to 20, and the circuit 12 of the first other port similarly has the first to third selecting circuits 15 to 17. And the first to third OR circuits 18 to 20, and the second other port circuit 13 is similarly configured. Thus, the circuits 11 to 13 all have the same configuration, and the circuits 11 to 13
The connection between them is made via a second selection circuit 16 and a third selection circuit 17 whose states are determined in advance by setting.

The transmission request signal RS from the data terminal device 14 and the control signal F from the first OR circuit 18 are input to the first selection circuit 15, and the first selection circuit 11 transmits the transmission signal RS depending on the state of the control signal F. The state of the request signal RS or the state of OFF as the signal A is referred to as the internal circuit of the DC branching device, the second OR circuit 19 and the third OR circuit.
Is output to the OR circuit 20.

A control signal B from the circuit 12 of the first other port and a control signal whose state is determined in advance are input to the second selection circuit 16, and the second selection circuit 16 receives the control signal B according to the state of the control signal.
The state of the control signal B or the unconditionally OFF state is output to the second OR circuit 18 and the third OR circuit 20 as a signal D.

The control signal C from the circuit 13 of the second other port and a control signal whose state is determined in advance are input to the third selection circuit 17, and the third selection circuit 17 receives the control signal C according to the state of the control signal. The state of the control signal C or the state of being unconditionally off is used as a signal E as the first OR circuit 18 and the second OR circuit 19.
Output to

The first OR circuit 18 receives the signal D from the second selection circuit 16 and the signal E from the third selection circuit 17 and calculates the logical sum of the signals to obtain the signal F. Output to 15.

The second OR circuit 19 receives the signal A from the first selection circuit 15 and the signal E from the third selection circuit 17, performs an OR operation, and inputs the result to the circuit 12 of the first other port. A signal G serving as the signal C is output.

The third OR circuit 20 receives the signal A from the first selection circuit 15 and the signal D from the second selection circuit 16, and becomes a signal B to be input to the circuit 13 of the second other port. H is output.

 Next, the operation will be described.

Here, the circuit 11 of the own port and the circuit of the first other port
12 is connected and disconnected from the circuit 13 of the second other port.

That is, the second selection circuit of the circuit 12 of the first other port
16 is set to output the OFF state unconditionally, and the third selection circuit 17 is set so that the signal C is output as it is as the signal E. Also, the circuit of the own port 11
The second selection circuit 16 is set so that the signal B is output as it is as the signal D, and the third selection circuit 17 is set so as to output the OFF state unconditionally. Also,
The second selection circuit 16 of the circuit 13 of the second other port is set so as to output the OFF state unconditionally.

Here, a case is considered where the transmission request signal RS is input to the data terminal device 14 or the circuit 11 of the own port, and then the transmission request signal RS is input to the circuit 12 of the first other port.

The transmission request signal RS from the data terminal device 14 is input to the first selection circuit 15 of the circuit 11, but since the first selection circuit 15 does not receive the signal F from the first OR circuit 18, , The first selection circuit 15 outputs the signal A to the internal circuit of the DC branching device, and also outputs the signal A to the second OR circuit 19 and the third OR circuit 20.

The second OR circuit 19 does not receive the signal E from the third selecting circuit 17 and outputs the signal G. The signal G is used as the signal C as the third selecting circuit of the circuit 12 of the first other port. Enter 17 The third selector 17 outputs the signal E to the first OR circuit 18.
And the third OR circuit 20 outputs the signal F to the first selection circuit 15. Therefore, the circuit 12 of the first other port
However, even if the transmission request signal RS from the data terminal device 14 is input, the transmission request signal RS is not output and the OFF state is output. When there is no input of the transmission request signal RS to the circuit 11 of the own port, the transmission request signal RS to be input to the circuit 12 of the first other port is output.

 Thus, the priority control of the transmission request signal RS is performed.

The circuits 11 to 13 constitute each unit priority control circuit, and the circuit configurations are all the same, and the circuits 11 to 13 may be connected by the number of connection ports required in the system, so that no circuit is wasted. . Even if there are additional ports, it can be easily handled.

In addition, by setting the second selection circuit 16 and the third selection circuit 17 in a predetermined state in advance, the ports can be easily grouped according to the number of necessary ports, thereby complicating the circuit configuration. Without any need, it can flexibly respond to various system needs.

[Effects of the Invention] As described above, according to the present invention, the unit priority control circuits of the ports to which the transmission request signals from the data terminal devices are input have the same circuit configuration, and the required number of ports are connected. Therefore, there is no waste in circuit scale. Further, even if the number of ports is increased, it can be easily handled.

Also, when it is necessary to group connected data terminal devices, it is possible to easily perform grouping according to the number of required ports, so that it is possible to meet various system needs without complicating the circuit configuration. It can respond flexibly.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing a conventional example. In the figure, 11: circuit of own port, 12: circuit of first other port, 13 ...
Circuit of second other port, 14 ... data terminal device, 15 ... first
, A second selection circuit, 17 a third selection circuit, 18 a first OR circuit, 19 a second OR circuit, 20
... third OR circuit, 21 ... selection circuit, 22,23 ... connection part, 2
4… Priority circuit, 25… Unit priority control circuit.

Claims (2)

(57) [Claims] An internal transmission request signal supplied from each transmission request signal line has a plurality of ports to which transmission request signal lines of a plurality of data terminal devices are respectively connected. A priority control circuit that selects only a transmission request signal and outputs the selected transmission request signal as a selected transmission request signal, and is supplied to each port from a corresponding port according to a selection signal that permits or inhibits the output of the selected transmission request signal. A selection circuit (21) for outputting an internal transmission request signal as a selection transmission request signal; and connection portions (22) and (23) that can be connected to a pair of other ports. Receiving a selection transmission request signal output from the selection circuit and supplying a selection signal indicating output inhibition to the selection circuit (21);
A unit priority control circuit (25) comprising a priority circuit (24) for supplying a logical sum signal of the output of the selection circuit (21) and the selection request signal of the other port to the other connection part (23)
A priority control circuit, comprising: 2. The circuit (11 to 13) of a plurality of ports connected to a plurality of data terminal devices has the same circuit configuration and is connected according to the required number of ports. A transmission request signal RS and a control signal F from the data terminal device are input, and the state of the transmission request signal or the off state is controlled by a control signal A.
A first selection circuit (15), which outputs a control signal B from the same circuit (12) of the first other port, and a control signal whose state is determined by a preset setting, and outputs the state of the control signal B Alternatively, a second selection circuit (16) that outputs an OFF state as a signal D, a control signal C from the same circuit (13) of a second other port, and a control signal whose state is determined in advance are input. A third selection circuit (17) that outputs the state of the control signal C or the off state as a signal E; and the signal D and the signal E are input, and the logical sum of the signals is taken to perform the first selection. A first OR circuit (18) that outputs a signal F serving as the control signal to be input to a circuit (15); a control signal A and the signal E that are input; Outputs a signal G serving as the control signal C to be input to the circuit (12) of another port That the second OR circuit (19)
And a third OR circuit for receiving the control signal A and the signal D, performing an OR operation on the control signal A and the signal D, and outputting a signal H serving as the control signal B to be input to a circuit (17) of a second other port. A priority control circuit comprising (20).