JPS6239577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data communication system, and more specifically, to a data communication system for performing data communication between a main terminal and a slave terminal by a polling method via a relay line.

In the polling method, multiple slave terminals are branch-connected to one line of the main terminal, a polling signal is sent from the main terminal to the line to designate and select a specific slave terminal, and a slave terminal corresponding to the polling signal is sent to the line. If only the terminal has data to be transmitted to the main terminal, it transmits it, and if it does not have this data, it transmits a signal indicating this (a termination signal to be described later).

If this conventional polling method is applied when the line from the main terminal is a relay line that includes a relay device or a trunk line, when the slave terminal does not have data to send, it will send a polling signal and data to send. A termination signal indicating that the polling signal is not available is transmitted through the trunk line, which causes disadvantages such as an increase in traffic on the trunk line's relay equipment and trunk line, and an abnormal state due to a delay in the polling signal at the relay equipment. . Therefore, it has been difficult to apply the conventional polling method to a system in which signals between a main terminal and a slave terminal must be transmitted through a relay line including a relay device.

An object of the present invention is to provide a data communication system using a polling method that can be advantageously applied when signals between a main terminal and a slave terminal must be transmitted via a relay line including a relay device.

The invention will now be explained in detail with reference to the drawings.

FIG. 1 is a block diagram schematically showing an embodiment of the present invention, in which TM is a main terminal, RM is a first relay device connected to the main terminal TM via line _L1 ,
R is a relay device for normal data communication, TD ₁ to _{TD o}
are the slave terminals, and RD is the second relay device connected to the slave terminals TD ₁ to TD _o by the line L ₄ (branch line in this case), and between the relay devices RM and R, and between the relay devices R and RD. They are connected by lines L ₂ and L ₃ , respectively. In this case, line L ₂ , relay device R
and line L ₃ constitute a trunk line. In addition,
A relay device (corresponding to R) can be further inserted into this relay line.

Figure 2 shows the main terminal TM, relay devices RM, R, RD.
FIG. 4 is a diagram showing a signal sequence between slave terminals TD ₁ and TD _o .

Figures 3 and 4 show the first terminal for the main terminal, respectively.
relay device RM and a second relay device for slave terminals
FIG. 3 is a block diagram showing an example of the configuration of RD. Note that FIG. 5 is a diagram showing a signal sequence in an abnormal state.

Next, the operation of this embodiment will be explained with reference to the drawings. Now, in order to receive data from, for example, the slave terminal TD ₁ , the main terminal TM transmits a polling signal S1 (polling ₁ ) for selecting the slave terminal TD 1 to the first relay device RM (see Fig. 2). .

This signal is sent to the first relay device RM via line _L1 .
It is received by the receiving circuit 1 of the first relay device RM (see Figure 3), and sent to the polling signal determining circuit 2, where it is determined whether or not it is a polling signal. Once determined, it is transferred to the polling comparison circuit 4.

The polling comparison circuit 4 has a storage section that stores the previous polling signal, and compares the contents of this storage section with the transferred polling signal. If it is determined that the signal has been transmitted, the signal is sent to the polling instruction signal creation circuit 5, which creates a polling instruction signal for the slave terminal _TD1 , and outputs the signal S2.
(As a polling instruction (see FIG. 2), it is sent to the trunk line _L2 via the transmitting circuit 6. At this time, the content of the storage section stores the polling signal received at this time.

Note that the polling comparison circuit 4 also sends a signal to the data waiting circuit 7 at this time. As will be described later, since no data has been returned from the selected slave terminal TD ₁ due to the above polling, the data waiting circuit 7
If the data to be sent back to the TM is not accumulated, the data waiting circuit 7 sends the data to the polling comparison circuit 4.
When a signal is received from , it sends a signal to the termination signal generation circuit 8 and controls it to generate a termination signal,
The signal is sent from the transmitting circuit 11 via the line _L1 to the main terminal TM as a signal S5 (termination) (see FIG. 2).

A termination signal is a signal that a slave terminal sends when it receives a polling signal to select itself and has no data to transmit to the master terminal, and that the master terminal receives this termination signal. This completes one cycle of polling.

When the main terminal TD receives this termination signal S5,
Furthermore, it sends a signal S6 (polling 1 for slave terminal TD ₁ ). This signal is received by the relay device RM in the same manner as described above, and is compared with the previously received polling signal in the polling comparison circuit 4. In this case, since it matches the one received last time, no signal is sent to the polling instruction signal generation circuit 5, and therefore no polling instruction signal is sent to the trunk line _L2 . However, a signal is sent to the data waiting circuit 7,
When there is no data in the circuit 7, a signal is sent to the termination signal generating circuit 8 in the same way as in the case described above, and a termination signal (signal S7, see FIG. 2) is sent from the transmitting circuit 11 to the main terminal TM.

In this way, the main terminal TM repeats sending the polling signal and the corresponding termination signal until data is returned from the slave terminal TD ₁ .

On the other hand, at the beginning of the above operation, the relay device
The polling signal instruction (Fig. 2, signal S2) sent from the RM to the trunk line _L2 is sent to the second relay device connected to the slave terminal via the relay device R and the trunk line _L3 .
Reach RD. Relay device R temporarily stores the received signal and transmits it, but does not convert the signal. The polling instruction signal S3 is sent to the relay device RD,
It is received by the receiving circuit 23 (see Figure 4) and transferred to the polling instruction determining circuit 22, where it is determined whether or not it is a polling instruction signal.If it is determined to be a polling instruction signal, this information is sent to the polling instruction signal. The polling signal is transferred to the transmitting circuit 24 and stored in its storage section, and the polling signal is sent as a signal S4 (see FIG. 2) from the transmitting circuit 21 to the line _L4 . The above signal S4 (polling 1) is similar to the signal S1 (polling 1) sent from the main terminal TM, and is transmitted to all of the plurality of slave terminals TD ₁ to TD _o branched and connected to the line L ₄ . sent to. Since this signal S1 or S4 is for the slave terminal TD1, it is received only by the slave terminal _TD1 , and if there is data to be sent back to the slave terminal _TD1 , it is sent back, and if not, a termination signal is returned. . In this case, no signal is returned from each terminal other than slave terminal TD ₁ (TD ₁ to TD _o excluding TD ₁ ).

If there is no data to be sent back to the slave terminal TD ₁ , a termination signal is sent back from the slave terminal TD ₁ to the relay device RD as a signal S12 (see FIG. 2). This termination signal S12 is received by the receiving circuit 25 of the relay device RD, and transferred to the termination signal determination circuit 26, where it is determined whether or not there is a termination signal, and when it is determined that it is a termination signal, the signal is sent as a polling signal. The polling signal previously received and stored in the circuit 24 is sent out as a signal S13 (polling 1) (see FIG. 2).

In this way, when there is no data to be sent back to the slave terminal TD ₁ , the polling signal and termination signal are repeatedly sent and received with the relay device RD.

If there is data to be sent back to slave terminal TD ₁ , slave terminal TD ₁ sends a polling signal (for example, signal S in Figure 2).
13), the data is sent as the signal S14 instead of the termination signal.

This signal S14 is transmitted to the receiving circuit 2 of the relay device RD.
5 and transferred to the termination signal determination circuit 26, where it is determined whether or not it is a termination signal. At this time, it is determined that the signal is not a termination signal, and the signal, ie, the data signal, is sent from the transmitting circuit 27 to the relay device R via the line _L4 as a signal S15. This signal S15 is relayed by the relay device R, and reaches the relay device RM via the line _L2 as a signal 16 (data).
It is received by the receiving circuit 10. The data is then transferred to the queuing determination circuit 9, where it is determined that the data should be queued, and transferred to the data waiting circuit 7, where it is stored.

When data is accumulated in the data waiting circuit 7, the main terminal TM sends a polling signal S8 (slave terminal
Polling 1) for TD ₁ ) is sent, this is received by the relay device RM, and when the data waiting circuit 7 receives the signal from the polling comparison circuit 4 by operating as described above, the data waiting circuit 7
Since data has been accumulated in , this data is transmitted from the transmitting circuit 11 to the main terminal TM via the line _L1 . That is, in response to the signal S8 sent from the main terminal TM as a polling signal to select the slave terminal TD ₁ , the above data is transmitted to the main terminal TM as a signal S9.
received at

After receiving this signal S9 (data from slave terminal TD ₁ ), the main terminal TM receives a signal S1 which is a data response signal.
0 to the rear terminal TD ₁ . This signal S10 is
It is received by the reception circuit 1 of the relay device RM, determined by the polling determination circuit 2 to be not a polling signal, and transferred to the signal generation circuit 3, and sent from the transmission circuit 6 to the line L ₂ (signal S17), the relay device R, and the line.
It is sent to the relay device RD via L ₃ (signal S18). This signal S18 is received by the receiving circuit 23 in the relay device RD, determined to be not a polling instruction signal by the polling instruction signal determining circuit 22, and transferred to the transmitting circuit 21, and sent to the slave terminal TD ₁ via the line L ₄ (signal S19). sent to.

When the slave terminal TD ₁ receives the signal S19 (data response), it sends out a signal S20 as a data end signal in response. This signal S20 is received by the receiving circuit 25 of the relay device RD, and transferred to the termination signal determination circuit 26, where it is determined that it is not a polling termination signal, and the signal S20 is sent to the line L ₃ (signal S21) from the relay device RD. R, line L ₂ (signal S22), and reaches the relay device RM as a data end signal.

This signal S22 is transmitted to the receiving circuit 10 of the relay device RM.
, the line is transferred to the waiting judgment circuit 9, where it is judged that no waiting is required, and the transmission circuit 11 disconnects the line.
It is sent to the main terminal TM via _L1 as a signal S11 (end of data). The main terminal TM receives this. Note that upon receiving the signal S22, the relay device RM erases the polling signal (in this case, the polling signal for the slave terminal TD ₁ ) stored in the polling comparison circuit 4 by means not shown. One communication cycle Co.1 is completed in the above manner.

For the next communication cycle, for example, from the main terminal TM,
To perform communication with the rear terminal TD ₂ (receiving data from the slave terminal TD ₂ ), a polling signal for selecting the slave terminal TD ₂ is sent as a signal S23 (polling 2), as shown in communication cycle Co.2. do. Then, communication is performed in the same manner as in the above communication cycle Co.1.

Next, the case of an abnormal state will be explained.
In the above communication cycle, when the main terminal is able to normally receive data from the desired slave terminal,
Even if the main terminal polls and selects the desired slave terminal, if the slave terminal does not have data and therefore no data is sent, the polling signal is switched to select another slave terminal during that communication cycle. It happens. However, if the former slave terminal obtains data to be sent to the main terminal almost at the same time as this switching, in response to the polling signal sent from the relay device RD,
Send this data. This data is
When the data is sent to RD, the relay device RD has already received the polling signal for the latter's slave terminal, so if the relay device RD responds to the polling signal and sends it back to the main terminal as data from the latter's slave terminal, that is, the former's An inconvenient situation occurs in which data from a slave terminal is accepted as data from the latter slave terminal.

In order to prevent the inconvenience caused by this abnormal state, the present invention further includes means. This will be explained next.

FIG. 5 shows a signal sequence for preventing inconveniences caused by the occurrence of such abnormal conditions.

In FIG. 5, the master terminal TM begins a communication cycle by sending a polling signal S1 that selects the slave terminal TD ₁ to receive data from the slave terminal TD ₁ . Similarly to the above, the polling instruction signal (signal S2
→S3) is sent to the relay device RD, and _a polling signal (signal S4,
S10, S12, etc.) and termination signals (signals S9, S1
1st prize) will be given and received.

At the main terminal TM, for example, if data is not returned, the sent signal is sent to another slave terminal, for example.
Change the polling signal to select TD ₂ [S8 (Polling 2)]. As shown in FIG. 3, this signal S8 is received by the receiving circuit 1 of the relay device RM, transferred to the polling signal determination circuit 2, where it is determined to be a polling signal, transferred to the polling comparison circuit 4, and the previously received signal S8 is sent to the polling comparison circuit 4. polling signal. In this case, since it is different from the previous one, the inside of the storage section is erased, and this result is sent to the polling instruction signal generation circuit 5, where a polling stop signal is generated, and the signal is transmitted through the transmission circuit 6 in the same manner as above. It is then transmitted to the relay device RD as signals S14 and S15.

In the relay device RD (see FIG. 4), this polling stop signal is received by the receiving circuit 23 and transferred to the polling instruction determining circuit 22, where it is determined that it is a polling stop signal. This determination result is sent from the polling instruction determination circuit 22 to the polling signal transmission circuit 24, which controls the transmission of the polling signal to be stopped even if a signal that has received the termination signal from the termination signal determination circuit 26 is input thereafter. The circuit 27 also transmits a stop confirmation signal.
It is then sent to line _L3 as signal S18 (stop confirmation).

Note that if data is returned from slave terminal TD ₁ before relay device RD receives the polling stop signal (signal S15 in FIG. 5), this is signal S.
13, S16, and S17 to the relay device RM, and stored in the data waiting circuit 7 in the same manner as above. At this time, after the polling stop instruction is issued from the polling signal comparison circuit 4, data transmission from the data waiting circuit 7 is suppressed and a termination signal S11 is sent to the main terminal TM.

After that, the relay device RM receives the above-mentioned stop confirmation signal (signal S17) at its reception circuit 10, and transfers it to the waiting judgment circuit 9, where it judges that it is a polling stop confirmation signal and sends it to the data waiting circuit 7. command to erase and discard the data accumulated here. Note that the polling signal (for the slave terminal TD ₂ in this case) stored in the polling signal comparison circuit 4 is erased by means not shown.

After the storage section of the polling signal comparison circuit 4 is erased, if the main terminal TM continues to send polling signals to the slave terminal TD ₂ , a new communication cycle starts in the same manner as described above, and the main terminal TM
Communication is performed to receive data from slave terminal TD ₂ .

In the above, the first relay device RM and the second relay device RM
In the polling method, the relay device RD is for the main terminal and the slave terminal, respectively, but the third relay device R may be a general purpose one, and there is no connection between the first and second relay devices RM and RD. , it is possible to use a relay line in which a plurality of such third relay devices R are inserted, and such a third relay device can be used not only for signal relay of this polling method but also for multiplex signal relay of other systems. It can be used for.

The present invention is not limited to the above embodiments, and various modifications can be made within the technical scope thereof.

Since the present invention is configured as described above, when a main terminal and a slave terminal in a polling method are connected via a relay line, the traffic on the relay line is increased by not sending signals specific to the polling method to the relay line. Furthermore, even if the above-mentioned abnormal condition occurs due to the delay in signal transmission by the relay line, correct communication can be carried out.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an outline of an embodiment of the present invention, FIG. 2 is a diagram showing a signal sequence in the embodiment shown in FIG. 1, and FIG. 3 is a diagram showing a signal sequence in the embodiment shown in FIG. A block diagram showing an example of the configuration,
FIG. 4 is a block diagram showing an example of the configuration of a second relay device for a slave terminal, and FIG. 5 is a diagram showing a signal sequence in an abnormal state according to an embodiment of the present invention. TM...Main terminal, TD ₁ to TDn...Slave terminal, RM
...First relay device for the main terminal, RD...Second relay device for the slave terminal, R...Third relay device,
L ₁ to _{L 4} ... Line, 1, 10, 23, 25 ... Receiving circuit, 6, 11, 21, 27 ... Transmitting circuit, 2
...Polling signal determination circuit, 3...Signal creation circuit, 4...Polling signal comparison circuit, 5...Polling instruction signal creation circuit, 7...Data waiting circuit, 8...Termination signal creation circuit, 9...Waiting Determination circuit, 22...Polling instruction signal determination circuit, 2
4...Polling signal transmission circuit, 26... Termination signal determination circuit.

Claims (1)

[Claims] 1 A first relay device connected to a main terminal that transmits a polling signal and receives data sent from a selected slave terminal, and a slave terminal that receives a polling signal and transmits a termination signal or data in response. A second relay device connected to a terminal, and a relay line connecting the first and second relay devices, and selected by the polling signal after the main terminal starts transmitting a polling signal. During one communication cycle until the return of data from the slave terminal is completed, when the first relay device receives the first polling signal from the main terminal, the first relay device transmits the polling signal to the slave terminal to the second relay device. At the same time, a termination signal is sent back to the main terminal, and if the polling signal received thereafter matches the previously received polling signal, the slave terminal is selected based on the polling signal. If the data sent from the terminal has not been received and stored, a termination signal is sent, and if the data has been received and stored, the data is returned to the main terminal.If a polling signal different from the polling signal received last time is received, The second relay sends a polling stop instruction signal to the second relay device via the relay line and receives a confirmation signal sent when the second relay device confirms reception of the polling stop instruction signal. The second relay device is configured to erase any data received from the device, and the second relay device receives the polling instruction signal sent from the first relay device via the relay line, and receives the polling signal. is sent to the slave terminal, and when a termination signal is received from the corresponding slave terminal, the above-mentioned polling signal is further sent repeatedly, and when a data signal is received, the sending of the above-mentioned polling signal is stopped, and the above-mentioned data signal is relayed to the above-mentioned. The signal is sent back to the first relay device via the line, and when a polling stop instruction signal is received from the first relay device, the transmission of subsequent polling signals is stopped and a confirmation signal is sent to the first relay device. A data communication method characterized by being configured to return data.