JP2552786B2 - Signal switching device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal switching device for switching connection states of various connecting devices such as a modem, an XY plotter, a personal computer and the like.

[0002]

2. Description of the Related Art The structure of a general signal switching device will be described. FIG. 15 is a conceptual diagram showing the structure of a signal switching device having, for example, four signal ports.
1 is a device main body, 2a to 2d are connected devices 3a to 3 respectively.
1st to 4th signal ports connected to d, 4 is the apparatus main body 1
The first signal port 2a and the second signal port 2
b, switching means for switching connection with any one of the third signal port 2c and the fourth signal port 2d.

With such a structure, the switching operation by the switching means 4 in the apparatus main body 1 is performed, whereby the first
The signal port 2a is connected to any one of the second signal port 2b, the third signal port 2c, and the fourth signal port 2d, that is, the connection device 3a is connected via the device main body 1,
It is adapted to be connected to any one of the connection devices 3b, 3c, 3d.

By the way, a signal switching device capable of command switching, such as an RS232C interface, in which a signal path switching operation is performed in accordance with a switching command from an external device, is conventionally constructed as shown in FIG. The portion corresponding to the switching means 4 of the interface LSIs 5a to 5d, the CPU 6 and the RAM 7
And ROM8.

That is, the interface LSIs 5a to 5d are arranged for the signal ports 2a to 2d, respectively.
The U6 temporarily receives all the signals arriving at the signal ports 2a to 2d, determines whether or not the received data corresponds to the switching command, and transmits the data to the transmission destination only when they do not correspond. When the received data corresponds to the switching command, the data is stored in the RAM 7 and the interface L is used based on the data.
The connection state between the SIs 5a to 5d is controlled to switch the signal path.

[0006]

However, such a conventional signal switching device capable of command switching has a complicated and expensive structure, and data that is a switching command is erroneously transmitted to a device as a transmission partner. There was a case where it was caused to cause an abnormal operation.

Further, in the conventional device shown in FIG. 16, an interface L is provided for each signal port (channel) 2a to 2d.
Since SI5a to 5d must be equipped, it is complicated and expensive, and the CPU 6 once receives a certain amount of data and then judges whether or not the command corresponds to the switching command, and then the data is sent to the other party. This is effective in a protocol such as a basic procedure that causes a delay in data transmission due to the transmission of data, causes flow control malfunction due to timing deviation, and does not send the next data until an acknowledgment code for confirmation is received. There is a problem in that the transmission speed is reduced and other adverse effects are caused.

Furthermore, since the conventional signal switching device cannot transmit signals other than the communication system, transmission speed, and format supported by the interface LSIs 5a to 5d, the signal line originally used by software has been used recently. In a high-speed file transfer program used by a unique method other than the usage method, there is also a problem that the device having the conventional configuration does not operate at all.

The present invention is intended to solve such a problem, and has a simple and inexpensive structure, and switches signal paths without causing erroneous transfer of switching commands, data transmission delay, and reduction in effective transmission rate. Another object of the present invention is to provide a signal switching device capable of reliably performing data transmission.

[0010]

In order to achieve the above object, a signal switching device of the present invention (claim 1) comprises an input / output /
In a system having at least three signal ports for either input or output and electrically switching and connecting each signal port, a fixed time is required after a first signal state change from the outside arrives at a predetermined signal port. When the second signal state change arrives within the predetermined signal port, removal means for suppressing signal transmission from the predetermined signal port to another signal port after the first signal state change is provided. It is characterized in that it is arranged between the other signal ports and provided with control means for controlling connection switching between the signal ports according to the change in the signal state removed by the removing means.

The removing means may be constituted by a low-pass filter (claim 2), and a detecting means for detecting a change of an input signal from the outside to the predetermined signal port and a detecting means of the detecting means. Timing means for starting timing by output, delay means for delaying the input signal by at least the detection reaction time by the detection means, and the timing means arranged between the delay means and the other signal port It may be configured by a signal holding unit that stops the signal transmission and holds the signal state while the time is being counted.
(Claim 3). When the apparatus according to any one of claims 1 to 3 is used for signal switching for serial communication, the removing means is interposed in the state control signal line connecting the signal ports (claim 4).

Further, it is equipped with a mode switching detecting means for detecting a change in the signal state within a fixed time to be removed by the removing means, and thereafter, the detection information of the mode switching detecting means provides recovery information to the predetermined signal port. The signal transmission from the predetermined signal port to the other signal port may be stopped until the arrival of the signal (Claim 5). At this time, when the signal transmission from the predetermined signal port to the other signal port is stopped after the signal state change within a fixed time is detected by the mode switching detection means, it is the same as the signal for starting the mode switching. Alternatively, the inverted signal may be sent to the signal line of the predetermined signal port (claim 6), or the signal holding means for holding the signal state before the first signal state change. When a signal state change within a fixed time is detected by the mode switching detection means, the signal from the predetermined signal port is switched to the signal information held by the signal holding means and the other signal port. It may be configured to output to (Claim 7).

In the device of claim 3 or 7, the signal holding means is provided for at least every two signal lines, and all the signal holdings are carried out when a signal state change occurs in at least one signal line. The means may be configured to shift to the signal holding state (Claim 8).

Also, bypass means for directly connecting the predetermined signal port and the other signal port, and a bypass means for putting the bypass means in a bypass state by a command from a connecting device connected to the predetermined signal port. A termination condition monitoring means for monitoring information from the predetermined signal port in the bypass state and ending the bypass state when the predetermined information arrives may be provided (claim 9).

Further, a non-changing time measuring means which is initialized at the completion of the time counting when the signal change interval of the predetermined signal port becomes a predetermined time or more, and is initialized at any change of the signal state during the time counting. And a bypass means for directly connecting the predetermined signal port and the other signal port, and the non-change time measuring means may be configured to put the bypass means in a bypass state during the time measurement of a predetermined time. Good (Claim 10).

[0016]

In the above-described signal switching device of the present invention (claim 1), when the second signal state change arrives within a fixed time after the first signal state change externally arrives at a predetermined signal port. In addition, after the first signal state change, the removing means inhibits signal transmission from a predetermined signal port to another signal port. By using a low-pass filter as the removing means (claim 2), the device of the present invention can be realized very simply and inexpensively.

Further, in the apparatus of claim 3, when the detecting means detects the change of the input signal from the outside to the predetermined signal port, the time measuring means starts the time measuring, and during the time measuring of the time measuring means, The signal holding means stops the signal transmission and holds the signal state from the delay means.

When the apparatus of the present invention is applied to serial communication, the removing means is provided in the state control signal line connecting each signal port (claim 4). Change cycle is a fraction of that of data signal line
By utilizing the characteristic, the switching command can be issued even when the communication speed of the data communication line is close to the limit of the transmission path.

According to another aspect of the present invention, when the mode switching detecting means detects a change in the signal state within a fixed time period to be removed by the removing means, thereafter, until the restoration information arrives at a predetermined signal port. During this period, signal transmission from a certain signal port to another signal port is stopped, so even if a signal change that does not fall within a certain time is given, this signal is transmitted to another signal port and It does not adversely affect the connected equipment. In addition, when the signal transmission from a predetermined signal port to another signal port is stopped by the operation of the mode switching detection means, a signal that is the same as or a signal obtained by inverting the signal for activating the mode switching is the signal of the predetermined signal port. By configuring to send to the line (claim 6), it is possible to notify the connected device connected to the predetermined signal port that the switching has been completed. Further, the signal state before the first signal state change is held by the signal holding means, and the signal from the predetermined signal port is converted into the signal information held by the signal holding means in accordance with the operation of the mode switching detection means. By switching and outputting to another signal port (Claim 7), the device connected to the predetermined signal port and the signal connected to the other signal port are kept active. It becomes possible to exchange information with the switching device and then reconnect the predetermined signal port to another signal port.

According to an eighth aspect of the invention, in the apparatus of the third or seventh aspect, the signal holding means is provided for at least every two signal lines, and when a signal state change occurs in at least one signal line. All the signal holding means are transferred to the signal holding state.

According to the ninth aspect of the present invention, the termination condition monitoring means causes the bypass means to directly connect the predetermined signal port to another signal port in response to a command from the connection device connected to the predetermined signal port. Meanwhile, the information from the predetermined signal port in the bypass state is monitored, and when the predetermined information arrives, the bypass state is ended.

In the apparatus according to the tenth aspect, the predetermined signal port and the other signal port are directly connected by the bypass means while the non-change time measuring means measures the predetermined time. The effect of signal delay can be reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a signal switching device (corresponding to claim 1) as a first embodiment of the present invention.
In FIG. 1, 1A is the apparatus main body of the first embodiment, and 2a.
2d are first to fourth signal ports provided in the apparatus main body 1A and connected to the connection devices 3a to 3d, 9 are transmission data signal lines, 10 and 11 are other signal lines, and these signal lines 9 Reference numerals 11 to 11 connect between the connection devices 3a to 3d and the apparatus main body 1A (each signal port 2a to 2d).

Further, 12 is a delay circuit for delaying the signal from the transmission data signal line 9 of the first signal port 2a by a detection reaction time by a short-term signal change detection circuit 13 described later, and 1
3 is a short-term signal change detection circuit (detection means) for detecting a signal change less than the minimum change time of data in communication between devices when it is received by the transmission data signal line 9 of the first signal port 2a, and 14 is a short-term signal change. A timer circuit (time measuring means) for starting time measurement by the detection output from the detection circuit 13, 15 is connected to the output side of the delay circuit 12 and is driven to open during the time measurement by the timer circuit 14 and shut off in the closed state at other times. This is a switch, and the delay circuit 12, the short-term signal change detection circuit 13, the timer circuit 14 and the cutoff switch 15 constitute a removing means 16.

This removing means 16 has a first signal port 2a.
When the second signal state change arrives within a fixed time after the first signal state change arrives from the outside, the first signal port 2a to the other signal ports 2b through after the first signal state change. The signal transmission to 2d is suppressed, and the first signal port 2a and the other signal ports 2b-2
It is arranged between d and.

The delay time by the delay circuit 12 is set to the time (detection reaction time) from when the signal reaches the short-term signal change detection circuit 13 to when the cutoff switch 15 is opened.

Further, 17a is a changeover switch for changing the connection between the cutoff switch 15 and the transmission data signal line 9 of each of the signal ports 2b to 2d, and 17b and 17c are the first signal port 2a and the second to fourth signal ports. 2b to 2d is a changeover switch for switching and connecting each of the signal lines 10 and 11, and the transmission data signal line 9 of the connection device 3a includes a delay circuit 12, a cutoff switch 15, and a changeover switch. While being connected to the connection devices 3b to 3d via 17a, the other signal lines 10 and 11 are connected to the connection devices 3b to 3d via the changeover switches 17b and 17c.

Reference numeral 18 denotes changeover switches 17a to 17 based on a signal from the transmission data signal line 9 of the first signal port 2a.
c is a control unit for interlocking switching control, and this control unit 18 is composed of a CPU, ROM, RAM, and a start-stop synchronization interface circuit of 76800 bps for decoding information of the transmission data signal line 9, and is connected from the connection device 3a. A signal conforming to the 76800 bps format is received as changeover information, and the changeover switch 17
a to 17c, which functions as a control means for controlling connection switching between the first signal port 2a and the other signal ports 2b to 2d in accordance with the change in the signal state removed by the removing means 16. Is.

With the above-described configuration, in the signal switching apparatus of the first embodiment, when the connection device 3a is communicating with any of the other connection devices 3b to 3d at a start-stop synchronization of 2400 bps, the minimum change time interval of data. That is, since the signal state change of less than 1/2400 second is not detected, the short-term signal change detection circuit 13 and the timer circuit 14 are inactive, and the cutoff switch 15 is closed. Therefore, the transmission data signal input from the connection device 3a to the transmission data signal line 9 of the first signal port 2a is delayed by the delay circuit 1
2, while being sent to any of the connection devices 3b to 3d of the other party via the cutoff switch 15 and the changeover switch 17a, and input from the connection device 3a to the other signal lines 10 and 11 of the first signal port 2a. Signal is sent via the changeover switches 17b and 17c, respectively, to the connected device 3 of the other party.
b to 3d.

At this time, the transmission data signal input to the transmission data signal line 9 of the first signal port 2a is also sent to the control section 18 at the same time.
Since the interval between signal state changes is sufficiently wide, the stop bit is not received by the asynchronous interface circuit, and this signal state change becomes invalid data.

When the connection device 3a changes the data transmission speed for switching and sends the switching information of 76800 bps, a signal state change of less than 1/2400 second occurs in the signal of the transmission data signal line 9, resulting in a short-term signal. Change detection circuit 13
Detects this and notifies the timer circuit 14. As a result, the timer circuit 14 immediately starts clocking and opens the cutoff switch 15 during clocking.

The switching information is delayed by the delay circuit 12 by the time from when the signal reaches the short-term signal change detection circuit 13 to when the breaking switch 15 is opened, and the switching information is output from the delay circuit 12. At that time, the cutoff switch 15 is opened, and the timer circuit 14 cuts off the cutoff switch 15 until all the switching information is discharged from the delay circuit 12.
The switching information is not transmitted to the other party's connected devices 3b to 3d because the open state of No. 2 is continued.

The control unit 18 receives the switching information from the connection device 3a and terminates the reception as normal data in the start / stop synchronization interface circuit. Therefore, this is judged to be valid data, and the changeover switches 17a to 17 are accordingly detected.
The switching control of c is performed.

As described above, according to the first embodiment of the present invention, the transmission data signal line 9 of the first signal port 2a is changed within 2 hours within a fixed time after the first signal state change from the connection device 3a. When the signal state change of the first time arrives, the removing means 16 suppresses the signal transmission of the transmission data signal line 9 from the first signal port 2a to the other signal ports 2b to 2d after the first signal state change. Information
The erroneous transfer of the (switch command) is prevented, and the signal path can be switched and the data can be transmitted reliably.

Next, referring to FIG. 2, a signal switching device (corresponding to claim 2) as a second embodiment of the present invention will be described. FIG. 2 is a block diagram showing its configuration. As shown in FIG. In the device body 1B of the second embodiment,
Instead of the removing means 16 of the first embodiment, a low-pass filter 19 which transmits data of 2400 bps or less is provided. That is, the transmission data signal line 9 of the signal port 2a connected to the connection device 3a is connected to the connection devices 3b to 3d via the low-pass filter 19 and the changeover switch 17a.
The other signal lines 10 and 11 are connected to the first
Similar to the embodiment, each of the connection devices 3b to 3d is connected via the changeover switches 17b and 17c.

With the configuration described above, in the signal switching apparatus of the second embodiment, when the connected device 3a is communicating with any of the other connected devices 3b to 3d in the asynchronous mode of 2400 bps, the low-pass filter 19 does this. Because it is transparent,
The transmission data signal is sent to any of the connection devices 3b to 3d of the other party via the low-pass filter 19 and the changeover switch 17a, and the connection device 3a outputs the first data signal.
The signals input to the other signal lines 10 and 11 of the signal port 2a are sent to any of the connection devices 3b to 3d of the other party via the changeover switches 17b and 17c, respectively.

At this time, the transmission data signal input to the transmission data signal line 9 of the first signal port 2a is sent to the control unit 18 at the same time as in the first embodiment.
In the control unit 18, since the interval of the signal state change is wide enough, the stop bit is not received by the start / stop synchronization interface circuit, and this signal state change becomes invalid data.

When the connection device 3a changes the data transmission speed for switching and sends the switching information of 76800 bps, this signal state change becomes the cut-off frequency of the low-pass filter 19, so that the switching information is connected to the other party. It is not transmitted to the devices 3b to 3d. In addition, the control unit 18
In this case, since the switching information from the connection device 3a is received and the reception is completed as normal data in the start / stop synchronization interface circuit, this is determined to be valid data, and the switching control of the changeover switches 17a to 17c is performed accordingly.

As described above, according to the second embodiment of the present invention, it is possible to obtain the removing means simpler and cheaper than the first embodiment, and obtain the same effect as that of the first embodiment. . In particular, the device of this embodiment is effective when the transmission line including the driver and the receiver can be driven at a frequency sufficiently higher than that of normal operation.

Next, a signal switching device (corresponding to claim 3) as a third embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a block diagram showing its configuration, and FIG. 4 is its operation. 3 is a timing chart for explaining FIG.
As shown in FIG. 7, the apparatus main body 1C of the third embodiment is provided with a removing means 16A having a structure different from that of the removing means 16 of the first embodiment.

The removing means 16A includes a delay circuit 12A,
Signal change detection circuit 13A, timer circuit (time measuring means) 14A
And a D latch (signal holding means) 20. The delay circuit 12A transmits the transmission data signal from the transmission data signal line 9 of the first signal port 2a to the signal change detection circuit 1
The signal change detection circuit 13A detects the state change of the transmission data signal from the transmission data signal line 9 of the connection device 3a.

The timer circuit 14A is a 200 μs retriggerable circuit which operates when a signal state change is detected by the signal change detection circuit 13A.
0 has its Q terminal connected to the changeover switch 17a, its D terminal receives the transmission data signal delayed by the delay circuit 12A, and its T terminal receives the output from the timer circuit 14A. The transmission data signal line 9 of the signal port 2a connected to the connection device 3a is connected to the connection devices 3b to 3d via the delay circuit 12A, the D latch 20 and the changeover switch 17a.

When the signal change detection circuit 13A detects a change in the state of the transmission data signal line 9, the information is output to the timer circuit 14A to activate the timer circuit 14A. As a result, the timer circuit 14A turns on the output and causes the D latch 20 to hold the data.
If the next change in the signal line does not arrive within a fixed time, the timer circuit 14A completes the time measurement, makes the D latch 20 transparent, and sends the output of the delay circuit 12A to the changeover switch 17a.

The above-mentioned D latch 20 functions as a signal holding means for holding the signal transmission in the stop signal state while the timer circuit 14A keeps time until a predetermined time. The configuration other than the removing means 16A described above is exactly the same as that of the first embodiment.

By the way, when the low pass filter 19 is used as the removing means as in the second embodiment, it is necessary to use an expensive high-order filter when the difference between the passing frequency and the blocking frequency cannot be made large. To do. Further, as shown in FIG. 4, unless the duty of signal change within a fixed time period of interruption is set to 50%, the low-pass filter 19 transmits this difference in duty as a low-frequency signal. The line change must be taken into consideration so that the duty becomes 50%, which becomes a burden when changing the signal state of the transmission data signal line 9 by a program. The device of the third embodiment solves such a problem with a small number of gates.

With the configuration described above, in the signal switching apparatus of the third embodiment, when the connection device 3a is communicating with any of the other connection devices 3b to 3d at the start-stop synchronization of 2400 bps, the transmission data signal line 9 is connected. Each time the state changes, the signal change detection circuit 13A and the timer circuit 14A operate,
The D latch 20 is caused to hold the information before the change. 240
Since the minimum signal line change time at 0 bps is about 417 μs, the timer circuit 14A waits 20 times after the signal state change.
Time measurement is completed after 0 μs, and the D latch 20 is set to the transparent state. As a result, the transmission data signal is transmitted to the changeover switch 17
The signals that are sent to any of the other connected devices 3b to 3d via a and are input from the connected device 3a to the other signal lines 10 and 11 of the first signal port 2a are respectively changed over to the changeover switch 17b. , 17c, and is sent to any of the connected devices 3b to 3d of the other party.

At this time, the transmission data signal is sent to the control section 18 at the same time as in the first embodiment.
In the control unit 18, since the interval of the signal state change is wide enough, the stop bit is not received by the start / stop synchronization interface circuit, and this signal state change becomes invalid data.

When the connection device 3a changes the data transmission speed for switching and sends the switching information of 76800 bps, the switching information is completed in a maximum of about 130 μs with a 10-bit structure including the start bit and the stop bit. Therefore, when the apparatus main body 1C of the present embodiment receives the switching information, the timer circuit 14A operates by the start bit to cause the D latch 20 to hold the information before the change, and in this hold state, the timer circuit 14A measures the time. At the time of completion, that is, from the last signal line state change including the stop bit to 200 μs, and after 200 μs has elapsed, the switching information has been transmitted, so the switching information is transmitted to the connection devices 3b to 3d of the other party. It will not be done. Further, the control unit 18 receives the switching information from the connection device 3a and terminates the reception as normal data in the start / stop synchronization interface circuit, so determines this as valid data and controls the switching of the changeover switches 17a to 17c accordingly. Do.

As described above, according to the third embodiment of the present invention, the connection device 3a is connected to the connection devices 3b to 3d of the other party while maintaining the transmission data signal line 9 in the communication state with the device main body 1C. It becomes possible to send control information.

If the connected device 3a sends the next control information before the timer circuit 14A completes the timekeeping, the connected device 3a is held when the control information is first sent to the connected devices 3b to 3d. Since the signal line status continues to be sent, it is possible to continuously send control information as well.
As in the case of using the low-pass filter 19 as in the second embodiment, part of the control information will not be transmitted to the connected devices 3b to 3d of the other party due to the duty of the signal of the control information.

Further, the delay time to be delayed in the delay circuit 12A is only a short time from the detection of the signal change to the activation of the timer circuit 14A, and the number of gates is suppressed to be small when the delay circuit is composed of a shift register. It will be possible.

Next, referring to FIG. 5, a signal switching device (corresponding to claim 4) as a fourth embodiment of the present invention will be described. FIG. 5 is a block diagram showing its configuration. Connected devices 3a to 3d are connected by RS232C,
The device of the present invention is applied when signal switching is performed for serial communication.

As shown in FIG. 5, the apparatus main body 1D of the fourth embodiment has substantially the same structure as that of the first embodiment, but in this fourth embodiment, 12B is the first signal port 2a. Delay circuit for delaying the signal from the CTS signal line (state control signal line) 9A by the detection reaction time by the short-term signal change detection circuit 13B, 13B is less than the minimum change time of data in inter-device communication, for example, 1/900 A short-term signal change detection circuit for detecting a signal change at an interval of less than a second when it is received by the transmission data signal line 9 of the first signal port 2a, and 14B starts timing by the detection output from the short-term signal change detection circuit 13B. The breaker switch 15 is a timer circuit, and like the first embodiment, the cutoff switch 15 is driven to be opened during the time counting by the timer circuit 14B and is kept closed at other times. . The delay circuit 12B, the short-term signal change detection circuit 13B, the timer circuit 14B, and the cutoff switch 15 constitute the removing means 16B of this embodiment.

The delay time by the delay circuit 12B is set to the time (detection reaction time) from when the signal reaches the short-term signal change detection circuit 13B to when the cutoff switch 15 is opened. In addition, as in the first embodiment, the CTS signal line 9A of the connection device 3a is connected to the delay circuit 12
While being connected to the connection devices 3b to 3d via B, the cutoff switch 15, and the changeover switch 17a, the other signal lines 10A and 11A are connected to the respective connection devices 3b to 3d via the changeover switches 17b and 17c. Has been done.

Further, 18A is C of the first signal port 2a.
Changeover switch 17 based on the signal from TS signal line 9A
The control unit 18A is a control unit for switching control of a to 17c in conjunction with each other.
PU, ROM, RAM and a 9600 bps start / stop synchronization interface circuit for decoding information on the CTS signal line 9A.
A signal conforming to the ps format is received as changeover information, and the changeover switches 17a to 17c are controlled accordingly.

With the configuration described above, in the signal switching apparatus of the fourth embodiment, when the connected device 3a is communicating with any of the other connected devices 3b to 3d in the start-stop synchronization of 2400 bps, the CTS signal line 9A changes. Normally, the cycle changes at intervals of 1/240 second or more, which is a fraction of the data length, so that both the short-term signal change detection circuit 13B and the timer circuit 14B become inactive, and the cutoff switch 15
Is closed. Therefore, the CT input from the connection device 3a to the CTS signal line 9A of the first signal port 2a
The S signal passes through the delay circuit 12B, the cutoff switch 15 and the changeover switch 17a, and the connected devices 3b to 3 of the other party.
The signal sent to any of the connection devices 3a and 3d from the connection device 3a and input to the other signal lines 10A and 11A of the first signal port 2a passes through the changeover switches 17b and 17c, respectively, and is the connection device 3b of the partner. ~ 3d.

At this time, the CTS signal is simultaneously sent to the control unit 1.
It is also sent to 8A, but in this control unit 18A,
Since the interval between signal state changes is sufficiently wide, the stop bit is not received by the asynchronous interface circuit, and this signal state change becomes invalid data.

When the connection device 3a sends switching information of 9600 bps to the CTS signal line 9A for switching,
A signal state change of less than 1/900 second occurs in the signal on the CTS signal line 9A, and the short-term signal change detection circuit 13B detects this and notifies the timer circuit 14B. As a result, the timer circuit 14B immediately starts timing, and the cutoff switch 15 is opened during the timing.

The switching information is delayed by the delay circuit 12B by the time from when the signal reaches the short-term signal change detection circuit 13B until the breaking switch 15 is opened, and the switching information is output from the delay circuit 12B. At that time, the cutoff switch 15 is opened, and all the switching information is in the delay circuit 1.
Since the disconnection switch 15 is kept open by the timer circuit 14B until it is discharged from 2B, the switching information is not transmitted to the connected devices 3b to 3d of the other party.

In the control section 18A, the switching information from the connection device 3a is received and the start / stop synchronization interface circuit completes the reception as normal data. Therefore, this is judged to be valid data, and the changeover switches 17a to 1 are accordingly selected.
Switching control of 7c is performed.

As described above, according to the fourth embodiment of the present invention, by utilizing the characteristic that the changing cycle of the CTS signal line 9A is a fraction of that of the transmission data signal line 9, the communication of the data communication line is performed. Even when the switching information is made to be able to be issued even when the speed is close to the limit of the transmission line, and even when the signal is delayed to pass through the removing means 16B, it does not affect the data communication line, so that effective communication is performed. It is not necessary to have an effect such as a decrease in speed, and it is possible to stop the effect on communication slightly.

Next, a signal switching device (corresponding to claim 5) as a fifth embodiment of the present invention will be described with reference to FIG. 6, and FIG. 6 is a block diagram showing its configuration. As shown in FIG. The apparatus main body 1E of the fifth embodiment is constructed in substantially the same manner as that of the first embodiment, but in the fifth embodiment, 21 indicates 50 μs for the signal from the transmission data signal line 9 of the connection device 3a. The transmission data signal line 9 of this embodiment is a removing circuit for removing signals within
1 and a mode switching flip-flop (FF) 23 described later
Shut-off switch 15 that is opened and closed by the switch, and changeover switch 1
7a and the connected devices 3b to 3d, and the other signal lines 10 and 11 are connected to the changeover switch 17
It is connected to the connection devices 3b to 3d via b and 17c.

Further, reference numeral 22 is a mode switching detection circuit which, when detecting a signal state change within 50 μs from the transmission data signal line 9 of the connection device 3a four times in succession, judges this as mode switching information and outputs it to the mode switching FF23. The mode switching FF 23 is set when the output from the mode switching detection circuit 22 is received and holds the output. The cutoff switch 15 is opened while the mode switching FF 23 is set.

Further, the control unit 18B of this embodiment uses the CP
U, ROM, output port for clearing the mode switching FF 23, and 2400 for decoding information on the transmission data signal line 9
It is configured by a start / stop synchronization interface circuit of bps, receives a signal conforming to the format of 2400 bps from the connection device 3a as the switching information, and controls the changeover switches 17a to 17c according to the information.

With the above configuration, in the signal switching apparatus of the fifth embodiment, when the connection device 3a communicates with any of the other connection devices 3b to 3d in the start-stop synchronization of 2400 bps, the signal line change within 50 μs. Is not detected, the mode switching detection circuit 22 and the mode switching FF 23
Are both inactive, and the cutoff switch 15 is closed. Therefore, the transmission data signal input from the connection device 3a to the transmission data signal line 9 of the first signal port 2a passes through the removal circuit 21, the cutoff switch 15 and the changeover switch 17a to the connection devices 3b to 3d of the other party. The signals that are sent to either one and input from the connection device 3a to the other signal lines 10 and 11 of the first signal port 2a are connected to the connection devices 3b to 3d of the other party via the changeover switches 17b and 17c, respectively. Be sent to any of the.

At this time, the transmission data signal is also transmitted to the control unit 18B at the same time, but in this control unit 18B, the output of the mode switching FF 23 is inactive, so that it is canceled by the AND gate 24 and the control unit 18B. 18B
Does not reach.

When the connection device 3a performs switching, first, a signal that inverts every 40 μs is continuously transmitted to the transmission data signal line 9. Since this signal changes its state within 50 μs, it is not removed by the removal circuit 21 and is not transmitted to the connected devices 3b to 3d of the other party.
Then, when the fourth signal state change is received, the mode switching detection circuit 22 determines the signal as the mode switching information and sets the mode switching FF 23 to active.
As a result, the cutoff switch 15 is opened, and subsequent signals are not transmitted to the connection devices 3b to 3d of the other party, and at the same time, the transmission data signal line 9 is connected to the start / stop synchronization interface circuit of the control unit 18B. . After that, the connection device 3a sends the recovery information at 2400 bps, and causes the control unit 18B to reset the mode switching FF 23.

As described above, according to the fifth embodiment of the present invention, the transmission data signal line 9 of the first signal port 2a is given a signal change within a fixed time to operate the mode switching detection circuit 22, and the operation thereof is performed. After that, even if a signal change that does not settle within a fixed time is given, this signal is not transmitted to the other signal ports 2b to 2d and does not adversely affect the connection devices 3b to 3d of the other party.

Therefore, after the signal transmission is stopped, the first
It becomes possible to send a slow signal, that is, a command, which is not restricted within a fixed time from the connection device 3a connected to the signal port 2a, to the apparatus main body 1E, and the control of the signal becomes easy. In particular, when the connected device 3a issues a command to the apparatus main body 1E by a program, the connected device 3a often causes a temporary delay in command transmission due to an interval interrupt or the like. By applying the above device, it is not necessary to exchange signals in a short time, and therefore the corner control becomes easy without giving special consideration to interrupts.

Next, a signal switching device (corresponding to claim 6) as a sixth embodiment of the present invention will be described with reference to FIGS. 7 and 8. FIG. 7 is a block diagram showing its configuration, and FIG. 8 shows its operation. 7 is a timing chart for explaining FIG.
As shown in FIG. 9, the device main body 1F of the sixth embodiment is configured almost the same as that of the fifth embodiment, but in the sixth embodiment, the loopback switch 25 is provided in the reception data signal line 10. The signal line 10 is interposed and connected to the connection devices 3b to 3d via the loopback switch 25 and the changeover switch 17b.

The loopback switch 25 is switched in interlock with the cutoff switch 15. When the cutoff switch 15 is opened, the loopback switch 25 is interlocked and connected to the transmission data signal line 9 side from the changeover switch 17b side. It is supposed to be done. This allows the loopback switch 2
Reference numeral 5 is a signal for activating the mode activation when the signal transmission from the first signal port 2a to the other signal ports 2b to 2d is stopped after the signal state change within the fixed time is detected by the mode switching detection circuit 22. A signal identical to or inverted from the above is sent to the signal line 10 of the first signal port 2a. Such a loopback switch 2
The apparatus of the sixth embodiment is constructed in exactly the same manner as the apparatus of the fifth embodiment shown in FIG. 6 except that 5 is newly provided.

With the configuration described above, in the signal switching device of the fifth embodiment, when the connection device 3a performs switching, first, as shown in FIG. 8, a signal to be inverted every 40 μs is continuously transmitted to the transmission data signal line 9. Send out. Since the signal state changes within 50 μs, this signal is removed by the removal circuit 21 and is not transmitted to the connection devices 3b to 3d of the other party, and the reception data signal line 10 is also the connection device of the other party. Three
The transmission of the transmission data signal line states of b to 3d is continued.

Then, when the fourth signal state change is received, the mode switching detection circuit 22 determines that it is the mode switching information and sets the mode switching FF 23 to active. As a result, the signal after the cutoff switch 15 is opened is not transmitted to the connected devices 3b to 3d of the other party, and at the same time, the loopback switch 25 is also switched from the changeover switch 17b side to the transmission data signal line 9 side. Then, as shown in FIG. 8, the information of the transmission data signal line 9 is looped back to the reception data signal line 10.

In the connection device 3a, the reception data signal line 10
Detects the loopback signal from the mode switch FF23
It is possible to confirm that the switch has operated (notification of completion of switching) with a simple and low-priced circuit, which makes it clear when to send the subsequent switching information and also to the connected device 3a.
On the other hand, when the apparatus main body 1F is not connected, this can be confirmed. The operation and effect other than the above points are exactly the same as those of the fifth embodiment, and therefore the description thereof will be omitted.

Next, referring to FIG. 9, a signal switching device (corresponding to claim 7) as a seventh embodiment of the present invention will be described. FIG. 9 is a block diagram showing its configuration.
As shown in FIG. 7, the device main body 1G of the seventh embodiment is constructed in substantially the same manner as that of the fifth embodiment, but in this seventh embodiment, the cut-off switch 15 of the fifth embodiment is replaced by D. A latch (signal holding means) 20A is provided. This D-latch 20A holds the signal state before the first signal state change. Therefore, the removal circuit 21 which is the input of the D-latch 20A is cut off at the time of interruption as in the second and third embodiments. It is composed of removing means for continuously transmitting the previous state.

The Q terminal of the D latch 20A is switched to the switch 1
7a, the transmission data signal from the removal circuit 21 is input to its D terminal, and the output from the mode switching FF 23 is input to its T terminal, which is connected to the connection device 3a. The transmission data signal line 9 of the signal port 2a is connected to each of the connection devices 3b to 3d via the removal circuit 21, the D latch 20A and the changeover switch 17a. As described above, the device of the seventh embodiment is configured in exactly the same way as the device of the fifth embodiment shown in FIG. 6, except that the D latch 20A is provided instead of the cutoff switch 15.

With the above configuration, in the signal switching apparatus of the seventh embodiment, when the connection device 3a communicates with any of the other connection devices 3b to 3d in the start-stop synchronization of 2400 bps, the signal line change within 50 μs. Is not detected, the mode switching detection circuit 22 and the mode switching FF 23
Both become inactive, the D latch 20A becomes transparent, and the transmission data signal input from the connection device 3a to the transmission data signal line 9 of the first signal port 2a is removed by the removal circuit 2.
1, while being sent to any of the other connected devices 3b to 3d via the D latch 20A and the changeover switch 17a, and input from the connected device 3a to the other signal lines 10 and 11 of the first signal port 2a. Signal is sent via the changeover switches 17b and 17c, respectively, to the connected device 3b of the other party.
~ 3d.

At this time, the transmission data signal is also transmitted to the control unit 18B at the same time, but in this control unit 18B, the output of the mode switching FF 23 is inactive, so that it is canceled by the AND gate 24 and the control unit 18B. 18B
Does not reach.

When the connection device 3a performs switching, first, a signal that inverts every 40 μs is continuously transmitted to the transmission data signal line 9. Since this signal changes its state within 50 μs, it is not removed by the removal circuit 21 and is not transmitted to the connected devices 3b to 3d of the other party.
Then, when the fourth signal state change is received, the mode switching detection circuit 22 determines the signal as the mode switching information and sets the mode switching FF 23 to active.
As a result, the D-latch 20A holds the data, and at this time, the output of the removing circuit 21 maintains the signal state before the first signal state change. Therefore, the information is notified to the destination connection devices 3b to 3d thereafter. Will continue to be sent. Since the operation thereafter is similar to that of the fifth embodiment, the description thereof is omitted.

The object of the device of the seventh embodiment of the present invention is that the connecting device 3a needs to hold the control signal in a constant state in order to maintain the active state of the device, for example, the DTR signal. In the case of a connection device such as a modem that disconnects the line when the signal is turned off, another signal is interrupted when the signal transmission from the first signal port 2a to the other signal ports 2b to 2d is interrupted. This is to maintain the active state of the connected devices 3b to 3d connected to the ports 2b to 2d.

Therefore, according to the device of the seventh embodiment configured as described above, the first signal port 2a is connected to the other signal ports 2b-2d while keeping the active state of the devices 3b-3d. The connected device 3a and the device main body 1G can exchange information, and then the first signal port 2a and the other signal ports 2b to 2d can be reconnected.

Next, referring to FIGS. 10 and 11, the eighth embodiment of the present invention will be described.
A signal switching device (corresponding to claim 8) as an embodiment will be described. FIG. 10 is a block diagram showing the configuration thereof.
1 (a) to 1 (c) are timing charts for explaining the operation thereof. As shown in FIG.
In the apparatus main body 1G of the embodiment, each connected device 3a to 3d23.
2C, and the RTS signal line 9B of the connection device 3a
And the DTR signal line 10A are respectively connected to the delay circuit 12
It is connected to the D terminals of the D latches 20B and 20C via C and 12D, and the Q terminals of the D latches 20B and 20C are connected to the signal ports 2b to 2d (the connected devices 3b to 20b) via the changeover switches 17a and 17b, respectively. 3d). The other signal line 11 of the connection device 3a is connected to the connection devices 3b to 3d via the changeover switch 10c.

Then, in the apparatus main body 1H of the eighth embodiment, the removing means 16C includes a pair of delay circuits 12C,
12D, a signal change detection circuit 13C, a timer circuit 14C, and a pair of D latches (signal holding means) 20B, 20C. Each of the delay circuits 12C and 12D includes an RTS signal line 9B or a DTR signal line 1 of the first signal port 2a.
The signal from 0A is delayed by the detection reaction time by the signal change detection circuit 13C.
3A is the RTS signal line 9B or DTR of the connection device 3a
The state change of the signal from the signal line 10A is detected.

The timer circuit 14C is a retriggerable 200 μs circuit which operates when a signal state change is detected by the signal change detection circuit 13C.
0B and 20C have changeover switches 17a and 17 for the respective Q terminals.
The signal delayed by the delay circuits 12C and 12D is connected to each D terminal, and the output from the timer circuit 14C is input to the T terminal thereof. R of signal port 2a to be connected
The TS signal line 9B is connected to the connection devices 3b to 3 via the delay circuit 12C, the D latch 20B and the changeover switch 17a.
The DTR signal line 10A is connected to the delay circuit 12D, the D latch 20C and the changeover switch 17b.
Is connected to each of the connection devices 3b to 3d via.

The signal change detection circuit 13C causes the RTS signal line 9
When a change in the state of the B or DTR signal line 10A is detected, the information is output to the timer circuit 14C to activate the timer circuit 14C. As a result, the timer circuit 14
C turns the output on and causes the D latches 20B and 20C to hold data. If the next change in the signal line does not arrive within a fixed time, the timer circuit 14C completes the time measurement, makes the D latches 20B, 20C transparent, and sends the outputs of the delay circuits 12C, 12D to the changeover switches 17a, 17b. It has become.

With the above configuration, in the signal switching device of the eighth embodiment, the state of the RTS signal line 9B or the DTR signal line 10A changes when the connecting device 3a is communicating with any of the connecting devices 3b to 3d. Each time the signal change detection circuit 13C and the timer circuit 14C operate, the D latch 20
B and 20C hold the information before the state change. RS
Since the change in the RTS signal line 9B and the DTR signal line 10A in 232C is sufficiently large compared to 200 μs, the timer circuit 14C completes the time measurement 200 μs after the change in the signal state, and makes the D latches 20B and 20C in the transparent state, thereby the RTS. The signals from the signal line 9B and the DTR signal line 10A are transmitted to any of the connection devices 3b to 3d via the changeover switches 17a and 17b.

The RTS signal is also sent to the control unit 18 at the same time, but since the control unit 18 has a sufficiently wide signal change interval, the start / stop synchronization interface circuit does not receive the stop bit, and this signal change is caused. It becomes invalid data.

Since the connection device 3a is switched, the RTS signal line 5 is changed as shown in FIG. 11 (a). At this time, the connected device 3a has the DTR arranged in the same register as the RTS.
Since the signal is also operated at the same time and this register is write-only and the current output state cannot be determined, the DTR is unconditionally set to "1". The signal state before change is assumed to be "0" for both RTS and DTR as shown in FIG. 11 (c).

In the device configuration of this embodiment, when a signal is applied as shown in FIG. 11C, the signal change detection circuit 13C operates at the time of rising of the DTR signal, whereby "0" immediately before the rising of DTR is generated. The "state" is held in the D latches 20B and 20C.

By the way, when the device of the seventh embodiment of the present invention described above is realized, a plurality of output signals of the connecting device which issues a command to the signal switching device are arranged in a register occupying one address, and If this register is a writable register, it becomes impossible to operate only the signal line 9 to which the mode switching detection circuit 22 is connected. For example, in an LSI called 8251 which is widely used at present, since RTS and DTR are arranged in the same register, there is no other way than to operate them at the same time, and since they are write-only registers, they are set in the register. It is also impossible to read the value that is stored. Furthermore, there are many cases where the procedure for setting in this register is different from the procedure for performing switching control, and it becomes impossible to hold the value to be set in the register in any memory and read it out to deal with it.

Under such a condition, when the signal change detection circuit 13C detects a change in the signal line within the predetermined time in the RTS as shown in FIG. 11A, the signal state of the RTS immediately before starting the output is In the case of FIG. 11B, no problem occurs, but in the case of FIG. 11C, the states of the signal lines connected to the same register are erroneously held. According to the eighth embodiment of the present invention, it is possible to avoid such a malfunction.

Next, referring to FIG. 12 and FIG. 13, the ninth embodiment of the present invention will be described.
A signal switching device (corresponding to claim 9) as an embodiment will be described. FIG. 12 is a block diagram showing the configuration thereof.
3 is a block diagram showing a multi-stage connection state of the signal switching device realized by this embodiment. As shown in FIG. 12, the device body 1J of the ninth embodiment is almost the same as that of the seventh embodiment. Although configured, in the ninth embodiment, the control unit 1
A bypass switch which is switch-driven by 8C and can directly connect the first signal port 2a and the other signal ports 2b to 2d.
A (bypass means) 26 is interposed between the Q terminal of the D latch 20A and the changeover switch 17a, and the transmission data signal line 9
The bypass switch 26 allows the changeover switch 17
The other signal ports 2b to 2d are directly connected via a, or the other signal ports 2b to 2d (connection are connected via the removing circuit 21, the D latch 20A, the bypass switch 26 and the changeover switch 17a). Connected to the devices 3b to 3d).

The bypass switch 26 is used in the control unit 18
Although it is switched and driven by C, the control unit 18C
While the bypass switch 26 is switched to the bypass state (the direct connection state between the first signal port 2a and the other signal ports 2b to 2d) by a command from the connection device 3a connected to the signal port 2a, the bypass switch 26 is in the bypass state. It functions as a termination condition monitoring means that monitors information from the 1 signal port 2a and terminates the bypass state when predetermined information arrives. Except for such a function of the control unit 18C, the control unit 18C is the same as the control unit 18B of the seventh embodiment, and the description thereof is omitted. Further, the device of the ninth embodiment is constructed in exactly the same way as the device of the seventh embodiment shown in FIG. 9 except that a bypass switch 26 is newly provided.

With the above configuration, in the signal switching apparatus according to the ninth embodiment, when the connection device 3a communicates with any of the other connection devices 3b to 3d at the start-stop synchronization of 2400 bps, the change of the signal line within 50 μs. Is not detected, the mode switching detection circuit 22 and the mode switching FF 23
Both become inactive, the D latch 20A becomes transparent, and the transmission data signal input from the connection device 3a to the transmission data signal line 9 of the first signal port 2a is removed by the removal circuit 2.
1, D-latch 20A, bypass switch 26, and changeover switch 17a via the connected devices 3b to 3d of the other party
And the signal input from the connection device 3a to the other signal lines 10 and 11 of the first signal port 2a via the changeover switches 17b and 17c, respectively. 3d.

When the connection device 3a performs switching, first, a signal that inverts every 40 μs is continuously transmitted to the transmission data signal line 9. Since this signal changes its state within 50 μs, it is not removed by the removal circuit 21 and is not transmitted to the connected devices 3b to 3d of the other party.
Then, when the fourth signal state change is received, the mode switching detection circuit 22 determines the signal as the mode switching information and sets the mode switching FF 23 to active.
As a result, the D-latch 20A holds the data, and at this time, the output of the removal circuit 21 maintains the signal state before the first signal state change. Therefore, the connected devices 3b to 3d of the other party thereafter receive the data. Information continues to be sent.

On the other hand, the information on the transmission data signal line 9 is connected to the start / stop synchronization interface circuit of the controller 18C.
The connection device 3a has a changeover switch 17a at 2400 bps.
Switching information is sent so as to switch. Next, the connection device 3a issues bypass switching information to operate the bypass circuit, and the control unit 18C accordingly switches the bypass switch 26 in the bypass direction and resets the mode switching FF 23.

Next, the connected device 3a is connected to another connected device 3b.
Mode switching is started for another signal switching device.
First, as in the previous case, 40 μs is applied to the transmission data signal line 9.
A signal that is inverted every time is continuously transmitted. At this time, in the device body 1J of the present embodiment, the signal is directly transmitted to the connection device 3b by the bypass switch 26. And
When the fourth signal change is received, the connection device 3b, which is a signal switching device having the same configuration as this embodiment, and the mode switching detection circuit 22 in the device body 1J shown in FIG. Set to active. As a result, the start / stop synchronization interface circuit in the device body 1J is connected to the transmission data signal line 9.

The apparatus main body 1J shown in FIG. 12 is configured so that only the mode switching information for determining the restoration information and the state transition is operated during the bypass operation, and therefore the connection device 3a is connected to the connection device 3b. Even if the switching information is sent to, it is ignored. Then, the connected device 3a is the connected device 3
When the recovery information is sent to b, the connection device 3b and the device main body 1J of this embodiment both respond to this, and the mode switching FF
23 and reset the bypass switch 26 to the D latch 2
The data signal path is formed by switching to the 0A side. When the connected device 3a sends the bypass information to the connected device 3b, the connected device 3b and the apparatus main body 1 shown in FIG.
J resets the mode switching FF 23, and the bypass switch 26 switches to the bypass side so that the signal switching device at the next stage can be controlled.

As described above, according to the ninth embodiment of the present invention, it is possible to connect the signal switching devices in multiple stages as shown in FIG. 13, and to connect the signal switching devices in multiple stages as shown in FIG. Also in the above, switching control from the connection device 3a is enabled.

Finally, referring to FIG. 14, a signal switching device (corresponding to claim 10) as a tenth embodiment of the present invention will be described. FIG. 14 is a block diagram showing the structure thereof.
As shown in FIG. 14, the device main body 1K of the tenth embodiment is
The structure is almost the same as that of the ninth embodiment, but in the tenth embodiment, a bypass switch (bypass means) 26A capable of directly connecting the first signal port 2a and the other signal ports 2b to 2d is provided. , The D latch 20A and the changeover switch 17a.
The bypass switch 26A causes the changeover switch 1
The other signal ports 2b to 2d are directly connected via 7a, or the removal circuit 21, the D latch 20A,
Other signal ports 2b to 2d (connected devices 3b to 3d) via the bypass switch 26A and the changeover switch 17a
Is connected to

In the present embodiment, the bypass switch 26A includes a no change time measuring timer (no change time measuring means) 27.
The non-change time measuring timer 27 starts timing by a signal change which does not fall within 50 μs after the completion of the timing, and restarts the timing even if any change is detected during the timing. While the timer 27 is clocking, the bypass switch 26A is set in the bypass direction (first signal port 2a and other signal ports 2b-2.
On the other hand, the bypass switch 26A is switched to the D latch 20A side when the timing is completed without any signal change for 1 second or more while switching to the direct connection state (d).
The device of the tenth embodiment is constructed in exactly the same way as the device of the seventh embodiment shown in FIG. 9, except that a bypass switch 26A and a non-change time measuring timer 27 are newly provided.

With the above configuration, in the signal switching apparatus of the tenth embodiment, when the connected device 3a communicates with any of the other connected devices 3b to 3d in the start-stop synchronization of 2400 bps, the no-change time measuring timer 27 is set. , Signal change is 50μ
Until it is judged that it is s or more and starts timing,
The transmission data signal is sent to any of the connection devices 3b to 3d of the other party via the removal circuit 21, the D latch 20A, the bypass switch 26, and the changeover switch 17a, and the connection device 3a outputs the first signal port 2a. The signals input to the other signal lines 10 and 11 of the other terminal are connected to the connection device 3b of the partner via the changeover switches 17b and 17c, respectively.
~ 3d.

The signal change interval of 2400 bps is 50 μs
Because of the above, the no-change-time measuring timer 27 starts clocking and switches the bypass switch 26A to switch the removing circuit 2
1 and the D latch 20A are bypassed. When such bypass is performed, the transmission data signal line 9 is directly connected to the connection device 3a and any of the other connection devices 3b to 3d, so that signal delay does not occur and communication throughput is improved. Further, since the signal change of 50 μs or less is transmitted after the bypass, it is possible to change the signal at intervals of 50 μs or less and perform high-speed data transmission.

When the connection device 3a performs switching, first, signal transmission is stopped for 1 second or longer, the time measurement of the no-change time measuring timer 27 is completed, and the bypass switch 26A is switched to the D latch 20A side. After that, a signal that inverts every 40 μs is continuously transmitted to the transmission data signal line 9 as a mode switching signal. Since the subsequent operation is exactly the same as that of the device of the seventh embodiment, its explanation is omitted.

As described above, according to the tenth embodiment of the present invention, it is possible to reduce the influence that the removing means delays the signal. That is, the mode switching detection circuit 2
In the case of sending the mode switching control signal to No. 2, by fixing the signal for the measured time of the no-change-time measuring timer 27 to the no-change state, and then giving the mode-changing signal that changes within a fixed time. The operation for the signal switching device is guaranteed, and only the first change is delayed for the continuous signal change in which the delay of the removing means adversely affects the communication between the connection devices 3a and 3b to 3d. However, there is no delay with respect to the second and subsequent signals. Therefore, a delay occurs in the processing such as the high-speed file transfer program described above in which the control signal is continuously operated. Therefore, the throughput does not decrease, and even if the first signal line change is transmitted without being accepted by the signal switching device, it is as if the signal switching device were Operate as if not continues, the influence of the signal switching device connected close to zero.

The present invention is not limited to the above-described embodiments, and any modification or the like within the scope of the present invention is included in the scope of the present invention.

[0107]

As described in detail above, according to the signal switching device of the present invention (claim 1), the signal is changed within a predetermined time after the first signal state change from the outside arrives at the predetermined signal port.
When the signal state change of the second time arrives, the removing means prevents the signal transmission from the predetermined signal port to another signal port after the first signal state change. There is an effect that transfer is surely prevented, and signal path switching and data transmission can be surely performed. Further, by using a low-pass filter as the removing means (claim 2), the device of the present invention can be realized very simply and inexpensively.

When the detecting means detects a change in the input signal from the outside to the predetermined signal port, the timekeeping means starts the timekeeping, and the signal holding means stops the signal transmission during the timekeeping of the timekeeping means. By configuring so as to hold the signal state from the delay means (claim 3), it becomes possible to send the control information to the connected device of the other party while maintaining the communication state.

When the device of the present invention is applied to serial communication, the removing means is provided in the state control signal line connecting each signal port (Claim 4). By utilizing the characteristic that the changing cycle is a fraction of that of the data signal line, the switching command can be issued even when the communication speed of the data communication line is close to the limit of the transmission path, and the removal command is passed. Even if you delay the signal to, because it does not affect the data communication line,
It does not have to affect the effective communication speed, etc.,
The influence on communication can be stopped to a minimum.

Further, when the mode switching detecting means detects a change in the signal state within a certain time period to be removed by the removing means, thereafter, a predetermined period is reached until the recovery information arrives at the predetermined signal port. By stopping the signal transmission from the signal port to another signal port (Claim 5), this signal is transmitted to another signal port and connected to the signal port even if a signal change that does not fall within a certain time is given Since it does not have an adverse effect on the equipment being used and it is not necessary to exchange signals in a short time, the corner control becomes easy without giving special consideration to interrupts.

When the signal transmission from a predetermined signal port to another signal port is stopped by the operation of the mode switching detecting means, a signal which is the same as the signal which activates the mode switching or a signal which is the inverted signal of the mode switching is applied to the predetermined signal port. By sending the signal to the signal line (claim 6), it is possible to notify the connected device connected to the predetermined signal port that the switching has been completed with a very simple and inexpensive structure.

Further, the signal state before the first signal state change is held by the signal holding means, and the signal from the predetermined signal port is held by the signal holding means in accordance with the operation of the mode switching detecting means. By switching to signal information and outputting to another signal port (Claim 7),
The device connected to the predetermined signal port and the signal switching device exchange information while keeping the active state of the device connected to the other signal port, and then the predetermined signal port and the other signal port. Can be reconnected.

By providing the signal holding means for every two signal lines and arranging all the signal holding means to shift to the signal holding state when the signal state change occurs in at least one signal line. (Claim 8) It is possible to avoid erroneously holding the state of the signal lines connected to the same register.

Furthermore, the termination condition monitoring means sets the bypass means to the bypass state in which the predetermined signal port and the other signal port are directly connected by the command from the connection device connected to the predetermined signal port, while the bypass is bypassed. By monitoring the information from the predetermined signal port in the state and ending the bypass state when the predetermined information arrives (Claim 9), the multistage connection of the signal switching device can be performed.

Furthermore, while the non-changing time measuring means measures the predetermined time, the predetermined signal port and the other signal port are directly connected by the bypass means (claim 10). It is possible to reduce the influence of the signal delay caused by, and to operate as if the signal switching device is not connected, and to almost eliminate the influence of the signal switching device connection.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal switching device as a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a signal switching device as a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a signal switching device as a third embodiment of the present invention.

FIG. 4 is a timing chart for explaining the operation of the device of the third embodiment.

FIG. 5 is a block diagram showing a configuration of a signal switching device as a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a signal switching device as a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a signal switching device as a sixth embodiment of the present invention.

FIG. 8 is a timing chart for explaining the operation of the device of the sixth embodiment.

FIG. 9 is a block diagram showing a configuration of a signal switching device as a seventh embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a signal switching device as an eighth embodiment of the present invention.

11A to 11C are timing charts for explaining the operation of the device of the eighth embodiment.

FIG. 12 is a block diagram showing a configuration of a signal switching device as a ninth embodiment of the present invention.

FIG. 13 is a block diagram showing a multistage connection state of a signal switching device realized by the device of the ninth embodiment.

FIG. 14 is a block diagram showing a configuration of a signal switching device as a tenth embodiment of the present invention.

FIG. 15 is a conceptual diagram showing a configuration of a general signal switching device.

FIG. 16 is a block diagram showing a configuration of a conventional signal switching device capable of command switching.

[Explanation of symbols]

 1A to 1H, 1J, 1K Device main body 2a to 2d Signal port 3a to 3d Connected device 9 Transmission data signal line 9A CTS signal line 9B RTS signal line 10, 11 Signal line 10A DTR signal line 12, 12A to 12D Delay circuit 13, 13B Short-term signal change detection circuit 13A, 13C Signal change detection circuit 14, 14A-14C Timer circuit 15 Breaking switch 16, 16A-16C Removing means 17a-17c Changeover switch 18, 18A-18C Control unit 19 Low-pass filter 20, 20A-20C D-latch 21 Removal circuit 22 Mode switching detection circuit 23 Mode switching flip-flop 24 AND gate 25 Loopback switch 26, 26A Bypass switch 27 No change time measurement timer

Claims (10)

(57) [Claims] 1. A signal switching device having at least three signal ports for any one of input / output / input / output, wherein each signal port is electrically switched and connected to a predetermined signal port from the outside for the first time. When the second signal state change arrives within a certain time after the signal state change of 1 comes, the signal transmission from the predetermined signal port to another signal port is suppressed after the first signal state change. Control means for controlling connection switching between the respective signal ports according to a change in the signal state removed by the removing means, while removing means for performing the removal is arranged between the predetermined signal port and the other signal port. A signal switching device characterized by being provided. 2. The signal switching device according to claim 1, wherein the removing means is composed of a low-pass filter. 3. The removing means includes a detecting means for detecting a change in an input signal from the outside to the predetermined signal port, and a time measuring means for starting time counting by a detection output of the detecting means.
A delay means for delaying the input signal by at least the reaction time detected by the detection means, and a signal provided while the timekeeping means is arranged between the delay means and the other signal port until the predetermined time is reached. 2. The signal switching device according to claim 1, further comprising signal holding means for stopping transmission and holding a signal state. 4. When performing signal switching for serial communication, the removing means is interposed in a state control signal line connecting the signal ports. Signal switching device. 5. A mode switching detection means for detecting a signal state change within a fixed time to be removed by said removal means is provided, and the detection output of said mode switching detection means thereafter provides recovery information to said predetermined signal port. 5. The signal switching device according to claim 1, wherein signal transmission from the predetermined signal port to the other signal port is stopped until the arrival of the signal. 6. A signal for activating mode switching when stopping signal transmission from the predetermined signal port to the other signal port after detecting a signal state change within a fixed time by the mode switching detection means. 6. The signal switching device according to claim 5, wherein the same signal as or a signal obtained by inverting the signal is sent to the signal line of the predetermined signal port. 7. A signal holding means for holding a signal state before the first signal state change is provided, and when the mode change detecting means detects a signal state change within a predetermined time,
7. The signal switching device according to claim 5, wherein the signal from the predetermined signal port is switched to the signal information held by the signal holding means and is output to the other signal port. 8. The signal holding means is provided for every at least two signal lines, and all the signal holding means shift to the signal holding state when a signal state change occurs in at least one signal line. The signal switching device according to claim 3 or 7, characterized in that: 9. A bypass means for directly connecting the predetermined signal port and the other signal port, and a bypass means for setting the bypass means in a bypass state by a command from a connecting device connected to the predetermined signal port. 9. An end condition monitoring means for monitoring information from the predetermined signal port in the bypass state and ending the bypass state when the predetermined information arrives.
The signal switching device described. 10. A non-changing timekeeping means that is initialized when the time of completion of the timekeeping is initialized when the signal change interval of the predetermined signal port becomes a certain time or more, and is initialized at any change of the signal state during the timekeeping. And a bypass means for directly connecting the predetermined signal port and the other signal port, and the non-change timing means puts the bypass means in a bypass state during the counting of a predetermined time. The signal switching device according to claim 1.