JPH03198556A - Terminal equipment changeover device - Google Patents

Abstract

PURPOSE:To automatically change over a channel connected to a terminal equipment when an ER signal is set by using the ER signal keeping its ON state during data communication independently of data transmission and reception. CONSTITUTION:When a request of a terminal equipment 161 making data communication with an opposite station through a MODEM 11 takes place, its ER signal changes from OFF into ON. A receiver 109 receiving the ER signal attended therewith brings its logic output into '0'. A selector 101 is activated to select an RS-232C interface signal line of a MODEM connection connector 11 to a connector 141 of a channel A thereby establishing the connection between the terminal equipment 161 and the MODEM 11. Thus, the data communication with the opposite station through the terminal equipment 161 and the MODEM 11 is attained.

Description

[Detailed description of the invention] [Summary] Regarding a terminal switching device used when one line terminating device is used by multiple terminals, each terminal in a communicable state is automatically switched to one line terminating device. The purpose is to be able to switch between terminals automatically and to ensure the connection status of terminals during data communication. channel selection means for selectively switching the line termination device to the first ER multiplied signal channel turned on to enable only that channel; and after the channel selection is performed by the channel selection means, the ER multiplied signal and timer means for maintaining the active channel to which the terminal is connected in the connected state during the period when the ER multiplier signal is turned on and for a predetermined period of time from the time when the ER multiplier signal is turned off.

[Industrial application field]

The present invention relates to a terminal switching device used when a plurality of terminals utilize one line termination bag W (modem, etc.).

[Prior art] Standard serial interface (standard R3-2320)
In the case of a line termination device such as a modem used for small-capacity communications, it is rare for one terminal to use it exclusively, and usually the modem is used in a time-sharing manner to connect multiple terminals (PCs). In many cases, one modem is sufficient for each TTY terminal (TTY terminal, etc.).

Conventionally, as a terminal switching method for using such a modem with multiple terminals, for example, Japanese Patent Laid-Open No. 55-1
This terminal switching method, known from Publication No. 2778, etc., is
The terminal is selected using the R3 signal (request sent by the terminal to the modem) of the R5-232C interface as a trigger.

[Problem to be solved by the invention]

However, the method of switching terminals using the R3 signal has the following problems.

In other words, in the case of half-duplex communication (one-way communication), if the own station is sending data, the other station cannot send data.
The R3 signal of R3-232C specification used for this is:
It turns on only when sending data, and turns off while receiving data. Therefore, during half-duplex communication, when the R8 signal of the own station is turned off in order to transfer the transmission right to the other station, the switching means that maintains the connection between the modem and the terminal is returned to its initial state. Therefore, if another terminal turns on the R3 signal and is in a waiting state, the terminal in the connected state is in a communicating state waiting for return data from the other station. There was an issue where the device would switch to another device during communication.

The present invention has been made in view of the above-mentioned points, and makes it possible to automatically switch each terminal in a communicable state to a single line termination device, and also to ensure the connection state of terminals during data communication. The purpose is to guarantee that

[Means to solve the problem]

FIG. 1 is a principle block diagram of the terminal switching device of the present invention.

In the figure, the channel selection means 1 includes a plurality of terminals 16 .
．． The terminals 16, . ER of 16□
When the double signal is turned on, the line termination device 11 is selectively switched to the ER double signal channel that was first turned on, and only that channel is made effective.

The timer means 2 determines the period T during which the ER multiplication signal is on after the channel is switched by the channel selection means 1.
The active channel to which the terminal is connected is maintained in the connected state for a predetermined time T from the time when the ER signal and the ER signal are turned off.

[For production]

When the whole device is idle, the terminal 16° or 16
When the ER multiplied signal of □ turns on, the channel selection means 1 operates with the ER multiplied signal turned on first, and the line termination device 11 is switched and connected to the channel to which the terminal that issued the ER multiplied signal is connected.

After being switched -1, the timer means 2 corresponding to the channel in the valid state operates for a period Te during which the ER double signal is on, and for a predetermined time T from the time when the ER double signal is turned off. Even if the ER multiplier signal of a channel is turned on, it will not switch to another channel (the connection of the valid channel will be maintained).

Therefore, in the present invention, by using the ER double signal that remains on during data communication regardless of whether data is being sent or received, the channel connected to the terminal with the ER double signal turned on can be automatically switched. and guarantee the connection of valid channels.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is an overall configuration diagram showing the connection state between one line termination device and a plurality of terminals to which the terminal switching device of the present invention is applied, and FIG. 3 is a configuration diagram showing a specific example of an automatic terminal switching device. It is.

First, in FIG. 2, an automatic terminal switching device 10 includes one line termination device, for example, a connection port 10 for a modem 11, and a plurality of channels, for example, two terminal connection ports 101 and 102.

A connector 12 and a cable 1 are connected to the modem connection port 101.
A modem 11 is connected via 3.

Terminal connection port 10. ．． 10. For each connector 1
4. ．． 14□ and cable 15. ．． Terminals 16+ and 16z are connected via 15□.

Also, 17. ．． 17□ is a display element such as an LED that displays the switching and operating status of each channel, and the display element 171 or 17. Only the light is lit.

The automatic terminal switching device 10, as shown in FIG.
R3-232C specification channel A connector 14. , the channel B connector 14□ with the same specifications to which the terminal 16□ is connected, and the R connector to which the modem 11 is connected.
3-232C specification connector 12, this modem connection connector 12, and channels A and B connectors 14. ．． 1
A selector lot selectively switches and connects each R3-232C interface signal between 4□, and channels A and B.
Each connector 14. , 14□, and each timer counter 1
A clock pulse oscillator 104 is provided for supplying clock pulses to signals 02 and 103.

The timer counters 102 and 103 measure the connection time T with the modem 11 when the corresponding channels A and B are in a valid state.
+ (see Figure 3), and is composed of, for example, 8 stages of flip-flops, and has a clock input terminal C.
K, clock enable terminal CKEN, clear terminal C
LR, preset terminal PR that presets the counter to all "1" and output terminal Q8 that takes out the output of the final stage.
It is equipped with

Each output terminal Q8 of the timer counters 102 and 103 has
The display element 17 . ．． 17
□ are connected to each other. Further, a clock pulse oscillator 104 is connected to each clock input terminal CK. Furthermore, each output terminal Q8 has a corresponding timer counter 1.
It is connected to the clock enable terminal CKEN of 02 and 103, and when the output of the output terminal Q is "1", the timer counter is disabled and counting operation is prohibited, and when the output of Q8 is 0"', it is enabled. This is to enable counting by a clock.

Each clear terminal CLR of timer counters 102 and 103
The receiver 109 and the OR gate 110 are connected in cascade.
Alternatively, the receiver 111 and the OR gate 112 are each connected. The receivers 109 and 111 receive and receive the ER double signal (terminal ready signal) of the corresponding terminal 161 or 16
In this case, the outputs of inverters 117 and 116 that invert the corresponding ER multiplied signal, each Q, and the output are powered by two people, and this turns on the ER multiplied signal and outputs the receiver 109 or 1.
When the logical output of channel 11 is 0'', the corresponding timer counter 102 or 103 is cleared, and the corresponding timer counter is restarted from the time when the ER double signal turns off, and when one channel is valid, the other There is a method to prevent the timer counter 102 or 103 of the channel from being cleared by the ER multiplication signal.

Further, a power-on reset signal is applied to each preset terminal PR of the timer counters 102 and 103, and when this power-on reset signal is turned on, each of the timer counters 102 and 103 Preset all to "1".

In addition, in FIG. 3, the timer counters 102 and 103
and receiver 109, 111, or gate 110.11
2 corresponds to the timer means 2 in FIG.
01 corresponds to channel selection means 1.

Next, the operation will be explained.

First, when the power is turned on to the terminal switching device and the power-on reset signal is turned on, all the flip-flops in each stage of the timer counters 102 and 103 are preset to "1°" and put into an idle state. At this time, the Q and output of each timer counter 102 and 103 are “
1", each display element 17., 17□ is held in the off state, and each clock enable terminal CK
Clock input from the oscillator 104 is prohibited by disabling EN.

In such a state, for example, the terminal 16. When a request for data communication with a partner station is issued through the modem 11, the ER signal changes from OFF to ON as shown in FIG. Along with this, the receiver 109 received the ER double signal.
sets its logical output to 0''.At this time, since the output of the inverter 117 is "0", the output of the OR gate 110 which receives this Ryokawa power as input becomes "0". When the output becomes '0', the clear terminal CLR which takes negative logic becomes 'L' and the timer counter 1
Clear 02. When the timer counter 102 is cleared, its Q8 output becomes "0'°, so the selector 101 that receives this output signal operates and connects the R3-232C interface signal line of the modem connection connector 11 to the channel A connector. Switch to 14., terminal 1
6+ and modem 11 are established. This enables data communication between the terminal 161 and the other party's station via the modem 11.

Note that each connector 14. ．． The symbols with 14 and 11 are defined in the R3-232C specification, and include ER: terminal ready, DR: modem ready, R3: terminal transmission request,
C3: modem transmission enabled, CD: carry detection, SD: transmission data, RD: reception data, SG: signal ground.

When the timer counter 102 is cleared by turning on the ER multiplication signal, the timer counter 102 maintains the clear state and the channel A also maintains the connection state with the modem 11 during the period Te during which the ER multiplication signal is on. Further, the display element 17° lights up to indicate that channel A is in use. At this time, since the output of the inverter 116 on the channel A side is '°1', the OR gate 112 which takes this output as one input disables the clear terminal CLR of the timer counter 103, thereby Even if the ER multiplication signal of the connected terminal 16z is turned on, the timer counter 103 is activated by this ER multiplication signal.
is prohibited from being cleared.

On the other hand, terminal 16. When the ER multiplied signal Te time (this time changes depending on the amount of communication data and is random) returns to off, the timer counter 102 that was kept in the clear state restarts and counts the clock from the oscillator 104. Begin to. As a result, the state of the timer counter 102 is all "1", that is, the time T shown in FIG.
When it counts until it reaches 1, its Q output becomes “1”.
”, the timer counter 102 enters the disabled state, prohibits the clock input from the oscillator 104, and returns to the idle state. Then, after T, the ER multiplier signal of the other terminal 16□ turns on. Then, in response to this, the switch 10 is switched to the channel B side in the same manner as in the above case.

Note that T and time are determined by the oscillation frequency f of the oscillator 104. Incidentally, in the case of this embodiment, T is TI=128/f (sec). Further, this T must be appropriately adjusted depending on the characteristics of the terminal, the response of the modem, the settings, etc., but is usually about 3 seconds.

In this way, when the automatic terminal switching device 10 is in the idle state, the modem 11
interface line is connected, and after that, the ER double signal is on for a period of Te, and the terminal remains in communication state for T3 hours from the time the ER double signal turns off, without switching to another channel even if other channels turn on the ER. and will maintain the connection with the modem.

That is, each terminal 16. ．． Since channel switching of the modem 11 to 162 is performed by the ER double signal, which is kept on during data communication regardless of whether data is being sent or received, it is possible to switch the channel of the modem 11 to However, it can solve the problem of suddenly switching to another terminal, and the terminal 16. ．． The switching of the modem 11 to 16□ can be performed automatically and reliably.

In addition, by guaranteeing the connection of the T3 time valid channel from the time the ER double signal is turned off, for example, if the terminal wants to continue data communication, but the ER signal is turned off momentarily at a data break for the purpose of clearing the data. Even if the terminal is in a waiting state by turning on the ER signal, the connection between the modem and the terminal that is attempting to continue data communication can be maintained without fail.

In addition, in the above embodiment, the case where the number of switching between the modem, that is, the line termination device and the terminal is 1:2, is described, but the present invention is not limited to this, and when increasing the number of channels, the number of switches is 1:2.
This can be realized by installing hardware that follows the same principle as shown in the figure for each channel.

〔Effect of the invention〕

As explained above, according to the present invention, for the terminal that first turns on the ER double signal, the line termination equipment is switched to the channel to which this terminal is connected, and after that, the ER double signal is turned on and the ER double signal is turned off. For a predetermined time T1 from the point in time, even if the ER multiplier signal of another channel is turned on, the connection of the active channel to the line termination equipment is maintained without switching to the other channel, so there is no need for human intervention. It is possible to automatically switch terminals in a communicable state to one line terminating device without any need, and it is also possible to stably and reliably guarantee the connection state of terminals during data communication.

[Brief explanation of drawings]

FIG. 1 is a principle block diagram of a terminal switching device according to the present invention. FIG. 2 is a configuration diagram showing the connection relationship between a terminal and a modem to which the present invention is applied. FIG. 3 is a block diagram showing an embodiment of an automatic terminal switching device according to the present invention. FIG. 4 is an explanatory waveform diagram of the ER multiplied signal in this embodiment. In the figure, 1 is a channel selection means, 2 is a timer means, 10 is an automatic terminal switch, 11 is a modem (line termination device), 12 is a modem connection connector, 14, . 14□ is a terminal connection connector, 16, . 16□
is a terminal, 101 is a selector, 102.103 is a timer counter, 104 is an oscillator, 109.111 is a receiver, 110.112 is an OR gate, 116.117 is an inverter, 171.17□ is a display element, 107.108 is a buffer be.

Claims (1)

[Claims] (1) Serial interface specifications (RS-23) corresponding to multiple terminals (16_1, 16_2)
2C), and the terminals (16_1, 16_
2) When the ER signal from
a channel selection means 1 for selectively switching a line termination device 11 to a signal channel to enable only that channel; and after the channel selection means 1 performs channel switching, the ER signal is turned on. During period Te and a predetermined time T_1 from the time when the ER signal is turned off,
A terminal switching device comprising: timer means 2 for maintaining a channel in a valid state to which the terminal is connected in a connected state.