JP2697687B2 - MODEM CONTROL SIGNAL SAMPLING METHOD AND COMMUNICATION SYSTEM USING THE SAME - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for sampling a modem control signal transmitted over a line cable connecting a plurality of terminal devices and a packet multiplexing device connecting them, and a communication system to which the method is applied. .

[0002]

2. Description of the Related Art Conventionally, in a communication system in which a plurality of terminal devices are interconnected unbalancedly with a packet multiplexer, a transmission clock is transmitted and guided from the packet multiplexer to each terminal device. The modem control signal is being sampled. Here, each terminal device and the packet multiplexing device are connected by a line cable, but a transmission line for a modem control signal (modem control line) is constructed on the line cable.

[0003]

In the communication system described above, there is a problem that induced noise is generated when sampling the modem control signal due to the induction of the transmission clock from the packet multiplexer.

[0004] Such generation of induced noise related to the modem control signal occurs on a line cable connecting between the terminal device and the packet multiplexing device when the power of the terminal device is turned off (when the power is turned off) (particularly, when the power is turned off). This occurs frequently when the line cable is long), but there is no circuit for removing the induced noise in the conventional communication system, so the induced noise generated when the modem control signal state is unstable is transmitted to the packet multiplexer. In this case, the packet multiplexer may incorrectly recognize the ON / OFF of the modem control signal, and as a result, the communication function may be affected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and a technical problem thereof is to provide a modem control signal sampling method which is not affected by induced noise and a communication system to which the method is applied. It is in.

[0006]

According to the present invention, a transmission clock is guided from a packet multiplexer to a plurality of terminal devices via a line cable, whereby the line cables are transmitted from the plurality of terminal devices. A method for sampling a modem control signal transmitted via the modem on the side of the packet multiplexing apparatus, wherein the packet multiplexing apparatus side transmits the modem control signal in accordance with the line speed information defining the line speed on the line cable. The state of the modem control signal is sampled based on the sample point information determined by calculating the sampling point for, and it is detected that the change in the state and the state after the change have continued for a specified amount as a result of the sampling. Notifying that the modem control signal has changed, and notifying that the specified amount has not been continued. If modem control signals sampling method of detecting again initialized is obtained.

On the other hand, according to the present invention, a plurality of terminal devices for outputting a modem control signal, a modem control signal is sampled, and a transmission clock for inducing the modem control signal is output to a plurality of terminal devices. A state of the modem control signal, which includes a packet multiplexing device to be transmitted and a line cable connected between the plurality of terminal devices and the packet multiplexing device, and which is transmitted by the packet multiplexing device via the line cable. A communication system having a plurality of modem control signal state detection units each performing detection,
A plurality of modem control signal state detection units, a line speed information unit having line speed information about the line cable, a sample point determination unit that calculates sampling points for the modem control signal according to the line speed information to determine sample point information, A sampling control unit that samples the state of the modem control signal based on the sample point information. Further, the plurality of modem control signal state detection units detect a change in state and a state after the change as a result of the sampling. A communication system having a determination unit for detecting a change in the modem control signal and notifying that the modem control signal has changed, and for not determining that the modem control signal has continued for the prescribed amount, initializing and detecting again.

Further, according to the present invention, in the above communication system, the plurality of modem control signal state detection units include an oscillator for generating an initial clock related to the transmission clock, and a transmission clock that divides the frequency of the initial clock to a predetermined value. And a frequency divider for obtaining the following.

Further, according to the present invention, in any one of the above communication systems, a communication system including a higher-level device connected to the packet multiplexing device via a network for performing data communication can be obtained. .

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, an outline of the modem control signal sampling method of the present invention will be briefly described. This method of sampling a modem control signal uses a method in which a transmission clock is induced from a packet multiplexing device side to a plurality of terminal devices via a line cable, so that the modem control signal transmitted from the plurality of terminal devices via the line cable is converted to a modem control signal. On the other hand, when sampling is performed on the packet multiplexer side, the packet multiplexer side calculates the sampling point for the modem control signal in accordance with the line speed information that defines the line speed on the line cable, based on the sample point information determined. It samples the state of the modem control signal. However, here, as a result of sampling, it is detected that the state change and the state after the change have continued for a specified amount, and it is determined that the modem control signal has changed. Initialize and detect again.

FIG. 1 shows a basic configuration of a communication system according to an embodiment to which such a modem control signal sampling method is applied. In this communication system, four terminal devices 1 to 4 for outputting a modem control signal, a modem control signal are sampled, and a transmission clock ST1 for inducing a modem control signal is output to each of the terminal devices 1 to 4. A packet multiplexing device 5 for transmission, a line cable connecting between each of the terminal devices 1 to 4 and the packet multiplexing device 5, and a network 6 for performing data communication
And a packet multiplexing device 5 via this network 6.
And a higher-level device 7 connected between the two.

Among them, the packet multiplexer 5 has four modem control signal state detectors 501 for detecting the state of the modem control signal transmitted via the line cable.
To 504 are provided.

FIG. 2 shows a local configuration of the communication system. Here, the terminal device 1 and the packet multiplexing device 5 are connected by a line cable 22, and the packet multiplexing device 5 is connected from the terminal device 1 via the line cable 22.
This shows that the modem control signal MC is transmitted to the terminal device 1 and the transmission clock ST1 is transmitted from the packet multiplexer 5 to the terminal device 1 via the line cable 22.

[0015] Here, the modem control in the modem control signals MC and the transmission in the terminal T ₁₁ of the packet multiplexing apparatus 5 clock ST1 and the terminal T ₁₄ of the transmit clock ST1 and the terminal T ₁₃ of the terminal T ₁₂ in the line cable 22 The signal MC is processed with waveforms and timings as shown in FIGS.

That is, the terminal T ₁₁ in the packet multiplexer 5
3A, the transmission clock ST1 as shown in FIG. 3A is output to the line cable 22, and the transmission clock ST1 as shown in FIG.
Transmitted to Moreover, the modem control signal MC is at the terminal T ₁₂ 3 transmitted from the terminal apparatus 1 into the line cable 22
Becomes an analog wave as shown in (c), a digital rectangular wave as shown in FIG. 3, terminal T ₁₄ of the packet multiplexing apparatus 5 (c). Here, an induction noise synchronized with the transmission clock ST1 is generated in the modem control signal MC by the induction of the transmission clock ST1 on the line cable 22, and the modem control signal MC is turned on / off. Incidentally, T _s in the figure shows one period of the transmission clock ST1,
x indicates a time from a change point of the transmission clock ST1 at which the induced noise of the modem control signal MC is synchronized to a point a which is not affected by the induced noise, as described later.

Therefore, each modem control signal state detection unit 50
1 to 504 have a configuration for sampling the modem control signal MC without being affected by induced noise.
As shown in the block diagram, a line speed setting register 31 as a line speed information section having line speed information on the line cable 22 and a sampling point for the modem control signal MC are calculated according to the line speed information to determine sample point information. And a sampling control unit 3 that samples the state of the modem control signal MC based on the sample point information.
5 are provided.

Each of the modem control signal state detectors 501 to 501
504 indicates that the change in the state and the state after the change have continued for a specified amount as a result of sampling, and determines that the modem control signal MC has changed. A determination unit 36 for initializing and detecting again, an oscillator 32 for generating an initial clock related to the transmission clock ST1, and a frequency divider 33 for dividing the frequency of the initial clock to a predetermined value to obtain the transmission clock ST1
And are provided.

The frequency divider 33 divides the frequency of the oscillator 32 according to the line speed information from the line speed register 31 to generate a transmission clock ST1. The sample point determination circuit 34 determines, based on the line speed information from the line speed register 31, the time from the change point of the transmission clock ST1 at which the induced noise of the modem control signal MC is synchronized to the point a not affected by the induced noise. x is determined, and the sample point information is notified to the sample control unit 35.
In the sample control section 35, the sample point determination circuit 34
, The state of the modem control signal MC at point a is sampled from the transmission clock ST1 output from the frequency divider 33, and the state result is transmitted to the determination unit. The judging unit 36 detects the state change and the state after the change from the sampling state result of the sampling control unit 35, and determines that the modem control signal MC has changed reliably only when the number of times is equal to or more than a predetermined number of times. To the processor or the like, but if sampling is not performed continuously k times, initialization is performed and detection is performed again.

FIG. 5 is a block diagram showing a basic configuration of the sample point determination section 34 provided in each of the above-described modem control signal state detection sections 501 to 504. The sample point determination unit 34 includes a first decoder unit 41, a multiplication unit 42, and a second decoder unit 43. The first decoder 41 calculates the period T _S of the transmission clock ST1 from the signal including the line speed information and outputs the result. The multiplying unit 42 determines in advance the set value S (the sample point determining element based on the phase of the transmission clock ST1:
0 <it has the S <1), determining the sample timing x (= T _S × _S) by performing a multiplication of period T _S and the set value S. The second decoder 43 outputs the time x to the sample controller 3
The signal containing the sample point information is converted to the counter value at the clock in 5 and transmitted to the sample control unit 35.

FIG. 6 is a block diagram showing a basic configuration of the sample control unit 35 provided in each of the above-described modem control signal state detection units 501 to 504. The sample control unit 35 includes a timing control unit 51, a counter unit 5
2 and a state detection unit 53. The timing control section 51 controls the operation timing of the counter section 52 and the state detection section 53. The counter 52 resets the counter value and starts counting by detecting the change point of the transmission clock ST1 synchronized with the induction noise, and generates a pulse when the count value of the sample point information transmitted from the sample point determination unit 34 is reached. I do. The state detection unit 53 samples the modem control signal MC when a pulse is input from the counter unit 52, and transmits the result to the determination unit 36.

FIG. 7 is a block diagram showing a basic configuration of the determination section 36 provided in each of the above-described modem control signal state detection sections 501 to 504. The determination unit 36
A sample accumulation control unit 61, a register unit 62 having first to k-th registers for holding the state of the sampled modem control signal MC, a modem control signal state register 63, a modem control signal state change register 64, a comparison unit 65, a result determination unit 66, a CPU notification control unit 67, and an activation control unit 68.

The sample accumulation control section 61 sequentially stores the sampling results transmitted from the sample control section 35 in the register section 62, whereby the state of k continuous modem control signals MC is sequentially stored in the register section 62. The modem control signal status register 63 stores status information of the modem control signal MC sampled in advance, and the modem control signal status change register 64 stores status change information. The comparing section 65 compares whether the status information of the register section 62 and the status information of the modem control signal status register 63 match the state indicated by all the registers, and the result determining section 66 determines the contents of all the registers based on the result of the comparing section 65. If they match, the state indicated by the modem control signal register 63 is determined to be the current state and notified to the CPU via the CPU notification control unit 67. If they do not match, the start control unit 68 is notified. Sends a reset signal to reset the peripheral blocks. Although the state of the modem control signal MC is kept the previous state, the start control unit 68 also resets the peripheral blocks to perform the start control when the state changes in the modem control signal state change register 64. .

In the embodiment, the packet multiplexing device 5
Although one modem control signal state detector 501 to 504 is provided, the number is not limited.

[0025]

As described above, according to the present invention, the state of the modem control signal is detected by sampling the portion of the modem control signal which is not affected by the induced noise due to the transmission clock ST1. Therefore, the accuracy of the detection of the state of the modem control signal is increased, and the malfunction of the packet multiplexer due to the induced noise of the modem control signal can be avoided.

[Brief description of the drawings]

FIG. 1 shows a basic configuration of a communication system according to an embodiment to which a modem control signal sampling method of the present invention is applied.

FIG. 2 shows a local configuration of the communication system shown in FIG.

3A and 3B are waveform charts and timing charts at respective terminal points shown for explaining a state of generation of induced noise in a local part of the communication system shown in FIG. 2; FIG. (B) relates to the transmission clock at another terminal in the line cable, (c) relates to the modem control signal at one terminal in the line cable, (d) relates to the other terminal in the packet multiplexer. And a modem control signal.

FIG. 4 is a block diagram showing a basic configuration of each modem control signal state detector provided in the packet multiplexer of the communication system shown in FIG. 1;

FIG. 5 is a block diagram showing a basic configuration of a sample point determination unit provided in each modem control signal state detection unit shown in FIG.

FIG. 6 is a block diagram showing a basic configuration of a sample control unit provided in each modem control signal state detection unit shown in FIG. 4;

FIG. 7 is a block diagram showing a basic configuration of a determination unit provided in each modem control signal state detection unit shown in FIG.

[Explanation of symbols]

 1 to 4, 23 line terminal device 5 packet multiplexing device 6 network 7 host device 22 line cable 31 line speed setting register 32 oscillator 33 frequency divider 34 sample point determination unit 35 sample control unit 36 determination unit 41 first decoder 42 Multiplication unit 43 Second decoder 51 Timing control unit 52 Counter unit 53 State detection unit 61 Sample accumulation control unit 62 Register unit 63 Modem control signal state register 64 Modem control signal state change register 65 Comparison unit 66 Result judgment unit 67 CPU notification control Unit 68 activation control unit 501-504 modem control signal state detection unit

Claims (4)

(57) [Claims] 1. A modem control signal transmitted from a plurality of terminal devices via the line cable by inducing a transmission clock from the packet multiplexer to a plurality of terminal devices via the line cable. In the modem control signal sampling method of performing sampling on the packet multiplexing device side, the packet multiplexing device side calculates a sampling point for the modem control signal in accordance with line speed information defining a line speed on the line cable. The state of the modem control signal is sampled based on the determined sample point information, and the change of the modem control signal is detected by detecting that the change in the state and the state after the change have continued for a specified amount as a result of the sampling. Notify and notify, and if not continued for the specified amount, initialize A method for sampling a modem control signal, comprising detecting again. 2. A plurality of terminal devices for outputting a modem control signal, and packet multiplexing for sampling the modem control signal, outputting a transmission clock for inducing the modem control signal, and transmitting the transmission clock to the plurality of terminal devices. And a line cable connected between the plurality of terminal devices and the packet multiplexing device, and the packet multiplexing device detects a state of the modem control signal transmitted through the line cable. A communication system having a plurality of modem control signal state detectors for performing each of the plurality of modem control signal state detectors, wherein the plurality of modem control signal state detectors includes a line speed information unit having line speed information on the line cable, and the line speed information. A sample point for calculating a sampling point for a modem control signal to determine sample point information. And a sampling control unit that samples the state of the modem control signal based on the sample point information, and further comprising the plurality of modem control signal state detection units, wherein the state change is performed as a result of the sampling. And detecting that the state after the change has continued for a prescribed amount and determining that the modem control signal has changed, and notifying the modem control signal, and if not continuing for the prescribed amount, initializes and detects again. A communication system comprising: 3. The communication system according to claim 2, wherein
The plurality of modem control signal state detection units may include an oscillator that generates an initial clock for the transmission clock, and a frequency divider for dividing the frequency of the initial clock to a predetermined value to obtain the transmission clock. A communication system characterized by the following. 4. The communication system according to claim 2, further comprising a higher-level device connected to the packet multiplexing device via a network for performing data communication.