JPH0318152A - Digital signal transmission system - Google Patents

Abstract

PURPOSE:To attain the accommodation to an exchange network without the revision of the software under flow control through a signal line by executing packet composition/decomposition of the change information of an interface signal between circuit terminating equipments and converting the information into a format capable of transmission through a packet conversion network similarly to the case of the data. CONSTITUTION:A line terminating equipment 2a receives and stores the data from a terminal equipment 1a, composes the data into the format of a data packet at every prescribed interval and sends the result to a line terminating equipment 2b through a packet exchange network 4. The terminating equipment 2b decomposes the packet, sends the data to a terminal equipment 1b, and when the change in a transmission requesting signal RS is detected, the data is composed into a packet for transmitting an interface signal and transferred to the line terminating equipment 2a via the packet exchange network 4. The terminating equipment 2a confirms the data to be for interface signal transmission by the packet classification part 11 of the packet 10 and controls a CS signal to the terminal equipment 1a.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention transparently transmits changes in the interface signal of a non-packet digital terminal to the other terminal, thereby directly connecting one terminal to another and transmitting the interface signal. The present invention relates to a digital signal transmission method that allows a system that performs flow control to be accommodated in a packet switching network.

[Conventional technology]

Currently, a serial transmission standard called RS-232G is rapidly being used for communication between terminals such as personal computers and word processors.

RS-232C is a standard that defines the interface between terminals and line termination equipment, but only the electrical and mechanical specifications of RS-232G can be used, such as directly connecting one terminal to another. It is also often used as a general-purpose interface where the signal line usage differs from the standard.

Figure 6 is an example of such a general-purpose interface.
RS-232C RS and CS lines are used as control signals for flow control.

However, in this way, terminal (1a) one terminal (lb)
When connecting directly between terminals, the distance between terminals is limited to a maximum of 20 m due to the electrical specifications of RS-232G.
Therefore, if there is a longer distance between the terminals, use the terminal (1a) using the interface signal line as described above.
Flow control between one terminal (1b) is not possible.

In addition, there are the following methods to solve such problems. For example, FIG. 7 is a diagram showing an example of the configuration of each communication device of the conventional interface signal transmission system disclosed in Japanese Patent Publication No. 64-7529.

This example shows a means for transmitting an interface signal to a partner terminal using a modem interface based on the RS-232C standard using RS and tliS lines, but it can also be easily applied to use as the general-purpose interface described above. In FIG. 7, terminals (la) and (lb) indicate digital terminals, and line termination devices (2a) . (2
b) comprises signal bit allocation means and send clear signal exit means. As shown in FIG. 8, the transmission side line termination device (2a) provides specific signals of one bit each as signal bits /DTf and DTr before and after the transmission data OT of transmission information, and one signal bit DTf. is used when there is a transmission request signal RS from the own terminal, and the other DT is assigned to the carry detection completion signal for checking the response from the other party.

The sending clear signal CS exit means is a clear sending signal generator (2g)
is set, and by checking the information of the signal bit DRr in the return information, if it is set, it is assumed that there is a response from the other party,
This is to transmit a send clear signal CS to the terminal (1a).

In addition, in FIG. 7, (2t) is a signal reception conversion device,
(3) indicates an exchange, and in FIG. 8, DR is return data, and DRf and DRr are 1-bit specific signals before and after the OR of the return data.

Next, we will explain the operation. In FIG. 7, a line termination device (2a) receives a transmission request signal R from a digital terminal (la).
When S is received, the transmission information is sent to the line termination device (2b) via the exchange (3). Line termination device (2b
), a signal reception conversion device (2t) is installed, and a terminal (1b) is installed.
When the transmission information for the terminal (lb) is received, a carry detection signal CD to that effect is sent to the terminal (lb), and as shown in FIG. 8, the signal bit oTt in the received transmission information is inserted into the signal bit DRr of the return information. and transmitting terminal (1a
) sends this information back to

The line termination device (2a) sends the return information shown in Figure 8 to the exchange (3).
), detects that the signal bit OR, is ゛゜1'', and sends the transmission request to the line termination device (2b).
know that you have reached. Then, a transmission enable signal CS is generated to the terminal (1a), and the transmission enable signal CS is transmitted to the terminal (1a).
).

The functions of each line termination device (2a) and (2b) operate in the same way as described above even if the transmission and reception are reversed. [Problems to be Solved by the Invention] As described above, in the configuration in which one terminal is directly connected, there is a problem that interface signals cannot be transmitted when the distance between the terminals is long. Further, in the conventional interface signal transmission method shown in FIG. 7, interface signal information is added to all data to be transmitted, which is wasteful and inefficient.

This invention was made in order to solve the above-mentioned problems, and it is a digital signal that prevents a decrease in transmission efficiency due to the transmission of interface signals, and also allows transmission of multiple interface signals with relative ease. The goal is to provide a transmission method.

(Means for Solving the Problems) A digital signal transmission system according to the present invention connects non-packet type digital terminals to a packet switching network via a line termination device having a packet assembly/disassembly function and performs communication between the terminals. In the digital signal transmission method of the packet switching network that has been realized, a packet consisting of a packet type section and an information section is used to transmit information between the line termination devices, and the non-packet type digital terminal sends data to the other terminal. When transmitting, information that can be identified as a data packet is added to the packet type section, and the packet with data stored in the information section is transmitted.When the interface signal of the non-packet terminal changes, information is added to the packet type section. In a line termination device that adds information that can be identified as an interface signal transmission packet, stores the interface signal state in the information section, and receives the packet via the packet switching network, the packet type section in the received information When the packet is a data packet, the data in the information section is transmitted to the receiving terminal, and when the packet type section is an interface signal packet, the interface signal information is transmitted to the transmitting terminal. As the interface signal state,
By controlling the interface signal to the receiving terminal, the interface signal information of the terminal is transparently transmitted to the other terminal.

[Effect]

In this invention, packet assembly/disassembly of interface signal change information is performed between line termination devices,
The information is converted into a format that can be transmitted over a packet-switched network like data. That is, the line termination device that detects a change in the interface signal packetizes the change information and transmits it to the partner line termination device only when the change occurs.

The line terminating device that receives this information reproduces the interface signal based on this information, thereby enabling transparent transmission of the interface signal.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram showing the configuration of an embodiment of this invention. In FIG. 1, terminals (la) and (1b) indicate non-packet digital terminals, and line termination equipment (2a)
, (2b) are equipped with packet assembly/disassembly functions and are connected to each other via a packet switching network (4). In this example, we will explain a method for realizing flow control using the control signal CS line indicating transmission permission on the packet exchange aw4 (4). In this method, as shown in FIG. 6, the transmission flow is controlled by turning ON/OFF the transmission enable signal CS in a direct line connection configuration. In Figure 6,
When the receiving terminal (1b) turns off the transmission request signal RS, the sending clear signal CS connected to it at the transmitting terminal (la) is turned off, so the transmitting terminal (1a) stops transmission. The receiving terminal (1b) sends the transmission request signal R
When S is turned ON, the CS signal is turned ON in the transmitting terminal (1a), and the transmitting terminal (1a) resumes transmission. For example, the packet transmitted through the packet switching network to notify the other line terminal device of the interface signal is
In figure format. This packet (lO) is composed of a packet type section (l1) for identifying the packet type and an information section (l2) for storing data or interface signal information. FIG. 3 shows examples of packet formats for data packets and interface signals.

The data packet stores data in the information section (l2), as shown in FIG.
The RS signal state S is stored in . When S is "l" or "o", it means that the RS signal is turned ON or OFF, respectively.

Next, the operation will be explained. In FIG. 1, a line termination device (2a) receives and stores data from a terminal (la), assembles the data into the data packet format shown in FIG. 3(a) at regular intervals, and exchanges the data. M4 (4)
It is transmitted to the line termination device (2b) via. The line termination device (2b) disassembles this and sends the data to the terminal (lb). At this time, the data is transferred to the receiving terminal (lb
) is transmitted at a speed that exceeds the processing capacity of
The terminal (lb) turns off the transmission request signal RS and requests suspension of transmission. The line termination device (2b) checks the state of the RS signal line at regular intervals, and when it detects a change in the transmission request signal RS from the terminal (lb), it transmits the information as shown in FIG.
It is assembled into packets for interface signal transmission shown in b) and sent to the line termination device (
2a) Forward to. The line termination device (2a) identifies this packet as being for interface signal transmission by the packet type section (11), and controls the CS signal to the terminal (la) according to the S bit.

Here, the line termination device (2a) has the configuration shown in FIG. That is, a terminal interface unit (20) that controls interface signals with the terminal and exchanges data, a buffer memory (2 lb) that stores data received from the terminal and data sent to the terminal, and a packet assembly timing and terminal interface signal inspection tie. a timer (24) for notifying switching, and a packet assembly/disassembly unit (22) that packetizes data received and accumulated from the line and disassembles packets received from the packet switching network (4).
, reception from the packet-switched network and the packet-switched network (4)
Buffer memory (2lb) for storing packets to be sent to
, a packet transmitting/receiving section (23) that transmits packets to the packet switching network (4), receives data from the packet switching network (4), and notifies the packet assembly/disassembly section (22) of receiving the packet.

When the line termination device operates as a transmitter, S
Data arrives from D and is sent to the terminal interface section (20
) is activated and stores the data received from the terminal in the buffer memory (21a).

The packet assembly/disassembly unit (22) is activated by the timer (24) at regular intervals to inspect the buffer memory (21a), and when data is being received, it is assembled into a data packet and sent to the buffer memory (2lb). ) and requests the packet transmitting/receiving unit (23) to transmit the packet. The packet transmitter/receiver section (23) that receives this transmits the packet toward the receiving side line termination device. Also, when an interface signal packet is transferred from the receiving terminal, the packet receiving unit (23) that received it
The packet assembling/disassembling unit (22) is activated, disassembles this packet, controls the terminal interface unit based on the RS signal state of the receiving terminal, and transmits the C to the transmitting terminal.
Change the S signal state.

On the other hand, when the line termination device (2a) operates as a receiving side, when a packet is sent from the transmitting side terminal, the packet assembling/disassembling unit (22) is activated by the packet transmitting/receiving unit (23) that receives the packet. and requests the terminal interface section (20) to disassemble this packet and send this data to the receiving terminal. The terminal interface section (20) that receives this transmits the data to the receiving terminal. In addition, in order to detect changes in the interface signal, the packet assembly/disassembly section (22) uses a timer (
24) is activated at regular intervals. When the packet assembly/disassembly section (22) detects a change in the interface signal, it assembles the interface signal packet shown in FIG. (2
3) to request packet transmission. The packet transmitting/receiving unit (23) that receives this transmits the interface signal packet toward the transmitting terminal.

Next, FIG. 5 shows the packet assembly/disassembly section (22) of FIG.
) is a flowchart showing the operation, and the operation will be explained according to the processing steps.

Step Sl F Reads the signal state of the RS line, inspects the state, and sets it to S.

It is in a state of waiting for the occurrence of a step Sl event.

When an event occurs, step 5 depending on its content.
Proceed to 3,58,511.

Step S3: Timer C notifies the timing to check the current signal state of the RS line.

Step S4: Compare the current signal state of the RS line and the previous signal state S, and if they are the same, proceed to step S2,
If they are different, the process advances to step S5.

Step S5: Record the current signal state in S as a new signal state of the RS line.

Step S6: Assemble an interface signal packet to wait for with S in the RS signal state.

Step S7: Instruct the packet transmitter/receiver to transmit the packet, and return to step S2.

Step S8: Notification of packet assembly timing is provided by the timer.

Step S9: By inspecting the contents of the buffer,
It is checked whether data is being received. If data is being received, the process advances to step 510; if not, the process advances to step S2.

Step 510: Packetize the data and proceed to step S7.

Step S11: The packet transmitter/receiver is notified of the reception of the packet.

Step S12: Inspect the contents of the control unit and determine the type of packet. If the data is for data, the process advances to step 513, and if it is for the interface signal, the process advances to step 515.

Step S13: Decompose the data packet.

Step S14: # Instructs the interface unit to transfer the received data, and returns to step S2.

Step S15: Decompose the interface signal packet.

Step 516: Control the interface signal with the terminal according to the content of the other terminal interface signal. In addition, in the above embodiment, the line termination device (2a) and (
2b) was explained as the sending side and the receiving side, respectively.
The operation is not limited to this example, and even if the receiving side and the transmitting side are reversed, the same operation as described above is performed.

Further, in this example, information is transmitted through two interface signal lines for transmission and reception, but there are n lines (n=1.2.3.
...) may be used for information transmission through the interface signal line, and the same effect as in the above embodiment can be achieved.

Further, in the above embodiment, flow control was described using the CS line, but other interface signals such as the RS line may be used, and the same effects as in the above embodiment can be achieved.

(Effects of the Invention) As described above, according to the present invention, a system performs flow control using a signal line in order to transparently transmit control signals between terminals between line termination devices via a packet switching network. can be accommodated in a packet-switched network without any changes to terminal settings or application software. Moreover,
Since the information on the signal line is transferred in packets between the line termination devices, it is possible to remove the restriction on the distance between terminals due to the electrical specifications of the general-purpose interface. In addition, since a packet is created only when the control signal changes, the impact on the network load due to control signal transmission is small, and even when the number of interface signal lines to be transmitted is increased, the increase in network load is small. .

[Brief explanation of drawings]

Figures 1 to 5 explain this invention.
Figure 2 is a block diagram of an embodiment of the present invention, Figure 2 is a packet structure diagram, Figure 3 is a diagram showing an example of the transmission format of data packets and interface packets, and Figure 4 is the configuration of a line termination device. 5 is a flowchart showing an example of the operation of the packet assembling/disassembling section in FIG. FIG. 8 is a diagram illustrating an example of a transmission signal of the conventional interface signal transmission system. In the figure, (la), (lb) ... terminal, (2a
), (2b)...Line termination device, (2g)...
- Generator of transmittable signal CS, (2t)...Signal reception converter, (3)...Switching equipment, (4)...Packet switching network, (10)...Packet, (11)... . . . Packet type section, (12) -- Information section, (20) . . . Terminal interface section, (21a) . (2lb)...
- Buffer memory, (22)...Packet assembly/disassembly unit, (23)...Packet transmission unit, (24)...Timer, DT,, DT1DR,,DR,...Signal bit, DT, OR...data, SD...transmission data,
RO...Received data, RS...Transmission request signal, CS
...Transmittable signal, CD...Carrier detection signal, ER
. . . Data terminal ready signal, DR . . . Data set ready signal. In each figure, the same reference numerals indicate the same or equivalent parts. (spontaneous) l. Incident display Plain poem 11N /-/Dayu/ζγ2. Name of invention Digital signal transmission method 3. Detailed description of the invention and drawings in the representative specification of the person making the amendment. L letter ga ■ 6. Contents of the amendment (1) The word "use" in lines 6 and 7 of page 3 of the specification is amended to read "specifications." (2) The statement "use" on page 4, line 6 of the specification is amended to "how to use." (3) The statement "bit/DTeJ" on page 4, line 12 of the specification is corrected to "bit DTt J." (4) The statement "inspected" on page ii, line 3 of the specification is corrected to "inspected". "Ori," he corrected. (5) The statement r (2lb) J on page 11, line 16 of the specification is corrected to r (21a) J. (6) The description "interface" on page 13, line 10 of the specification is corrected to "interface." (7) The statement "wait" on page 14, line 18 of the specification is amended to "have". (8) Figure 4 of the drawings shall be corrected as shown in the attached sheet. 7. Catalog of attached documents
1 or more

Claims (1)

[Claims] In a digital signal transmission system for a packet-switched network in which communication between terminals is realized by connecting non-packet-based digital terminals to a packet-switched network via a line-terminating device that has packet assembly/disassembly functions, A packet consisting of a packet type section and an information section is used for information transmission, and when the non-packet type digital terminal transmits data to the other party's terminal, information that can be identified as a data packet is added to the packet type section. , and transmits a packet storing data in the information section, and when the interface signal of the non-packet terminal changes, information that can be identified as an interface signal transmission packet is added to the packet type section, and the interface signal is added to the information section. In the line termination device that stores the signal state and receives the packets via the packet switching network,
The packet is identified by the packet type section in the received information, and if it is a data packet, the data in the information section is transmitted to the receiving terminal, and if the packet type section is an interface signal packet, the packet is transmitted to the interface. A digital signal transmission system characterized in that interface signal information of a terminal is transparently transmitted to a partner terminal by using signal information as an interface signal state of the transmitting terminal and controlling an interface signal to the receiving terminal. .