JPS59204340A - Communication system - Google Patents

Abstract

PURPOSE:To change communication modes, packet by packet, by setting a communication mode in the mode setting part of a packet when packeting and sending out information from plural stations connected to a common transmission line. CONSTITUTION:Plural stations (ST) are connected to the common transmission line and terminal devices are connected to the respective STs to constitute a system which performs mutual communication. When each ST packets and sends out information in said system, the mode setting part 60 is provided in the data packet, and a binary number corresponding to one of communication modes I - IVis set in the setting part 60. No answer packet is sent back in communication mode I , and an answer packet is sent back in mode II; and subsequent communication is carried out in III after communication in I , and subsequent communication is carried out in IV after commumication in II. Each ST receives this packet and set its communication mode according to the mode setting part.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a communication system in which a plurality of stations are connected through a common transmission path.

Conventional configuration and its problems FIG. 1 shows an example of the configuration of a conventional communication system.

In FIG. 1, 1 and 2 are terminal devices, 3 is a transmission line, 4 to 8 are taps, 10 to 14 are stations, and 2o to 27 are computers 1. This is a terminal device such as a facsimile or telephone. These terminal devices 20-27 can communicate with each other via the stations 10-14 to which they are connected.

FIG. 2 shows an example of a frame structure of a data packet in a conventional communication system. In FIG. 2, 30 is a start delimiter, 31 is a receiving address, 32 is a source address, 33 is a control section, 34 is information, 36 is a frame check section, and 36 is an end limiter.

FIG. 3 shows an example of the configuration of a transmission/reception control section of a station in a conventional communication system. 40 is a transmission buffer, 41
4 is a transmission control circuit, 42 is a frame check code creation circuit, and 4 is a transmission control circuit;
3 is a delimiter addition circuit, 4 is a parallel-to-serial converter circuit, 46 is a transmitting circuit, 46 is a receiving circuit that performs synchronization and waveform shaping, 47 is a signal detection circuit, 48 is a collision detection circuit, 4
9 is a serial-parallel conversion circuit, 60 is a delimiter and address decoder, 61 is a frame inspection circuit, 52 is a reception control circuit, 53 is a reception buffer, 54 is a CPU, 5
5 is a timer, and 66 is a DMA controller.

Communication between these stations 10-14 is performed as follows. Now, when the station 10 receives a transmission request from the terminal device 20 to the terminal device 26 connected to the station 14, the CPU 64 transfers information from the terminal device 20 to the transmission buffer 4.
After transferring the data to o, a transmission request is issued to the transmission control circuit 41,
Enter the sending state. The station 1o that has entered the transmission state monitors the signal on the transmission path with the signal detection circuit 47, and if there is no signal, the frame check code generation circuit 42 and the delimiter addition circuit 43 packetize the information (hereinafter referred to as data packet). The parallel-serial conversion circuit 44
The signal is subjected to parallel-to-serial conversion and transmitted to the transmission line via the transmitting circuit 46. If a signal is detected on the transmission path, the data packet is sent out after waiting for the signal to disappear on the transmission path.

By the way, each station monitors the transmission path by the signal detection circuit 47, and sends out data packets as soon as the signal disappears. Therefore, if multiple stations simultaneously receive transmission requests from terminal devices and send out data packets, When transmitted, data packets collide on the transmission path.

The station controller that is transmitting data packets monitors collisions on the transmission path using the collision detection circuit 48. When a collision is detected, the station controller stops transmitting the data packets, waits for an appropriate time that varies depending on the station, and then transmits the data packets again. Send out. In this way, the above operation is repeated until the transmission is successful.

On the other hand, station 1, which is not transmitting data packets,
1 to 14 also monitor the signal on the transmission line by the signal detection circuit 47, and compare the receiving address of the received data packet with the address of the own station in the decoder 6o. If the address matches the address of the own station, the reception control circuit 52 is notified of reception of the data packet. The reception control circuit 62 stores the received data packet in the reception buffer 63 while checking the received data packet for errors in the frame checking circuit 61. If an error is detected, the data packet is discarded. , if there are no errors,
The reception control circuit 62 indicates that the data packet has been received.
Inform PU64.

The 0PU 64 notifies the terminal device 26 that the data packet has been received, and uses the DMA controller 66 to transfer the information stored in the reception buffer 63 to the terminal device 26 . In this way, the data packet sent from station 1o is sent to station 14, and a series of communications is completed.

This communication control method is C8M/OD ((farri)
erSenSe Multiple Access W
It is called the ith Co11ision Detection) method.

In such communication between stations, the receiving station sends an acknowledgment if the data packet was successfully received, in order to clarify whether it has indeed received the data packet or not.
If the packet cannot be received, a negative response is returned (hereinafter, these responses are referred to as response packets).

By the way, since these response packets are sent out under the same conditions as data packets from other stations, there is a risk of collisions occurring between the data packets sent out from each station controller, and the time required to send a response back is reduced. There was an inconvenience that no decision was made. A system that improves this drawback is: - All stations other than the receiving station monitor the signal on the transmission path, and when a signal is detected on the transmission path, the receiving station returns a response packet. and the time required for the destination station to return the response packet to the source station.
A method has been proposed in which response packets are prevented from colliding by postponing the transmission of data packets from the own station.

Both of the above methods each have their own characteristics. The former is effective when no response is returned between stations, and the latter is effective when a response is returned between stations. However, some of the information held by the station requires a response, while other information, such as information that requires real-time performance, does not require a response. There are also cases where information from terminals connected to a station is multiplexed and sent. As described above, there are various forms of communication (hereinafter referred to as communication modes), and if the communication mode is fixed as in the above method, it will be difficult to handle different types of information.
It has the disadvantage that it cannot be handled flexibly and reduces communication efficiency.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, to flexibly deal with different types of information, and to communicate efficiently.

Structure of the Invention The present invention provides a mode setting section in a data packet, and when a station sends out a data packet, sets a communication mode according to information in the mode setting section and sends out the data packet. The station operates according to the mode set in the mode setting part of the detected data packet, thereby making it possible to change the communication mode for each packet.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described. The present invention is not concerned with the form of the communication system, the transmission path, the number of stations and the number of terminals connected to the system. For ease of explanation, the bus-type communication system shown in FIG. 1 will be explained here as an example. Note that the same components as those in the conventional example are given the same numbers and their explanations are omitted.

Furthermore, the present invention is characterized by changing the communication mode for each packet depending on the type of information, but in order to clarify the effects and practicality of the invention, the following four communication modes will be explained as examples. .

■, Mode I: Communication mode that does not return response packets ■, Mode Il: Communication mode 1 that returns response packets, Mode I: Communication mode that continues communication after a response packet has been sent back ■, Mode ①: Communication mode in which communication continues after a response packet is returned. These communication modes are set for each packet using the data packet frame mode setting unit 60 shown in FIG. Since four communication modes are considered here, 2 bits is sufficient for the mode setting section 6o.

If you want to set more communication modes, just make the mode setting section larger. FIG. 6 shows the correspondence between communication modes and mode setting section 60. Mode 1 is “00” (2
(Hexadecimal number) Mode ■ is "01," mode ■ is "10," and mode ■ is "11."

Next, operations in each communication mode will be explained.

The operation in mode (2) will be explained using FIG.

FIG. 6 is a diagram showing signals detected on the transmission path at each station, with the horizontal axis as the time axis.

Now, suppose that station 1 (hereinafter referred to as ST1) receives a request from the terminal 20 to transmit information such as voice that does not require a response packet to the terminal 22 of station 2 (hereinafter referred to as ST2).
The data packet 70' sent out by ST1 propagates on the transmission path and is received by other ST2 to ST5, and only ST2 sets the destination address and its own station's address. Since the addresses match, data packet 7o is taken in. All stations read the mode setting section 6 of a0 in the data packet.
It operates in mode I according to the communication mode of 0.

In this mode, the receiving destination ST2 does not need to send back a response packet, so the series of information transmission ends here. Therefore, if ST2 to ST6 receive the data packet 70, ST1 still sends out the data bucket (70), and each of them can send out the next data packet.

The operation in mode (2) will be explained using FIG.

FIG. 7 is a diagram showing signals detected on the transmission path at each station, with the horizontal axis as the time axis.

Now, if ST1 receives a request to send information that requires a response from the terminal 21 to the terminal 23 of ST3, ST1 sets the mode setting section 60 of the data packet 80 to "01" and sends the data packet 80. The data packet 80 sent by ST1 propagates on the transmission path and is received by other stations ST2 to ST5, and only ST3 takes in the data packet 8o because the receiving address and the address of the own station match. The station operates in mode 2 according to the communication mode of the mode setting section 60 of the data bucket) 80. In this mode, the receiving station ST3 needs to return the response packet 81, so ST3 operates according to the state of its own station. Therefore, the other stations ST1-2, ST4-6 receive the response packet 81 in the time required to return the response packet 81 (corresponding to twice the maximum propagation delay time within the communication system). only to postpone sending.

After receiving the response packet 81, the data packet is transmitted. After sending out the response packet 81, ST3 can send out a data packet.

The operation in mode (2) will be explained using FIG.

FIG. 8 is a diagram showing signals detected on the transmission path at each station, with the horizontal axis as the time axis.

Suppose that ST1 receives almost simultaneously a request from the terminal 2o to the STs' terminal 26 for information that does not require a response, and from the terminal 21 to the ST4's terminal 24 for information that requires a response. At this time, since it is more efficient to send the image information in the same communication sequence than to send the image information separately, ST1 continuously sends the image information. ST1 is the information that was requested first (
Here, the information from the terminal 20) is set to "10" in the mode setting unit 60, and is packetized and sent. The data bucket) 90 sent by ST1 propagates on the transmission path and is received by STs from other stations ST2,
Only in ST5, since the receiving address and the own station's address match, the data packet 90 is taken in.

All stations operate in a mode according to the communication mode of the mode setting section of the data packet 90. In this mode, the destination station ST6 does not need to send back a response packet, but since the data packet 91 is sent out following ST1, the next data packet 91
The transmission of the data packets owned by the own station is postponed for a certain period of time (corresponding to the maximum propagation delay time within the communication system) until the station arrives.

After sending the data packet 9o to ST5, ST1 sends the next data packet 91 to the STA within a certain period (corresponding to the maximum propagation delay time within the communication system). This time, ST1 does not send any data packet following this data packet 91, so this data packet 91
is set to mode ■. The operation of each station in response to the data packet 91 set to mode (2) is the same as in the case of FIG. 6, and only ST5 returns the response packet 92, and the series of communications ends. Here, continuous transmission of two data packets is taken up as continuous communication, but there is no limit to the number of data packets that can be continuously transmitted.

The operation in mode (2) will be explained using FIG. 9.

FIG. 9 is a diagram showing signals detected on the transmission path at each station, with the horizontal axis as the time axis.

Suppose that ST1 receives almost simultaneously from the terminal 2o a request to send information that does not require a response to the terminal 26 of ST5, and from the terminal 21 to the terminal 24 of ST4 that requires a response. At this time, since it is more efficient to send the image information in the same communication sequence than to send the image information separately, ST1 continuously sends the image information. ST1 sets the mode setting unit 6° to '11', packetizes and transmits the previously requested information (in this case, information from the terminal 21).

The data packet 100 sent by ST1 propagates on the transmission path, is received by other stations ST2 to ST5, and is sent to s
Only for 'r4, since the receiving address and the address of the own station match, the data packet 16o is taken in. All stations operate in mode (2) according to the communication mode of the mode setting section of the data packet Oo. In this mode, the destination station ST4 needs to send back the response packet 101, so ST4 sends the affirmative or negative response packet 1 depending on the state of its own station.
Return o1. Therefore, other stations 5T1-3
, ST6 postpones the transmission of the data packet held by its own station for the time required to return the response packet (response bucket) +o+ (corresponding to twice the maximum propagation delay time within the communication system).

After returning the response packet 101, ST4 also transmits the data packets owned by its own station for a certain period of time (corresponding to the maximum propagation delay time in the communication system) until the next data bucket (102) arrives for the same reason. postpone. After receiving the response packet 1o1, ST1 sets the next data packet 102 to mode 1 and sends it out.

The operation of each station with respect to the data packet 1o2 set to mode I is similar to that shown in FIG. 4, and after the station receives the data packet 102, the series of communications ends. Here, continuous transmission of two data packets is taken up as continuous communication, but there is no limit to the number of data packets that can be continuously transmitted.

In this way, the communication mode can be changed for each packet depending on the type of information, and communication can be performed efficiently.

FIG. 10 shows an example of the configuration of the transmission/reception control section of the station according to the present invention. Note that the same components as those in the conventional example are given the same numbers and their explanations are omitted.

The above communication mode setting is performed as follows.

At the source station, this is done by setting the mode setting section 6o in the data packet to the corresponding communication mode. In stations other than the source station, the mode setting section 60 in the received data packet
is set in the mode setting circuit 110 according to the result of decoding by the decoder 60. However, the mode setting is performed only when the result of frame inspection of the received data packet is that there is no error in the frame and there is no collision among the received data packets.

FIG. 11 is an example of a state transition diagram showing the operation of each station in the present invention. Taking these communication modes as examples, the operation of each station is described in the following four states.

Condition 1: Eye, Doll Care 2. A97. Care, A4A State 3: Waiting for response packet State 4: Waiting for continuous communication The arrows in FIG. 11 indicate the direction of transition, and the logical expressions above the arrows indicate the conditional expressions for transition. Each symbol in the logical formula is data: data packet reception, ACK: response packet reception, AD
is address matching, TX is data packet transmission, (I) ~
(IV, ) represents the communication mode of the received data packet, - means negative aggregation, 1'' if each condition is met, and 0'' if not.

Transition between states occurs when the conditional expression is logically correct, that is, equal to '1'. At this time, the processing shown in brackets [ ], such as returning a response packet and setting a timer period, is performed.

Next, transitions between states in the state transition diagram of FIG. 11 will be explained.

■ If the station is in state 1.

If the following conditions are met, the state remains in state 1 (a).

- Receive a data packet, and its mode setting section is mode (IV).

- Receive a data packet, its mode setting part is mode OD, and the addresses match. At this time, the station returns a response packet.

- A data packet in mode (1) was sent.

- A mode (IV) data packet was sent.

If the following conditions are met, the process moves to state 2.

- Receive a data packet, its mode setting section is mode (1), and the addresses match. At this time, the station returns the response bucket and sends the Taiho 2D
and wait for data packets.

- Receive a data packet and its mode setting section is mode (1). At this time, the station sets the timer to D and waits for a data packet.

If the following conditions are met, the process moves to state 3 (a).

- Receive a data packet, its mode setting section is mode (It), and the addresses do not match. At this time, the station sets the timer to 2D and waits for a response packet.

- A data packet in mode (1) was sent.

At this time, the station sets the timer to 2D and waits for a response packet.

- Send data packet in mode (n).

At this time, the station sets the timer to 2D and waits for a response packet.

If the following conditions are met, the process moves to state 4 (No).

- A data packet is received, its mode setting section is mode (1), and the addresses do not match. At this time, the station sets the timer to 3D and waits for a data packet or response packet.

- A response packet was received. At this time, the station sets the timer to 3D and waits for a data packet or response packet.

■ If the station is in state 2.

If the following conditions are met, the state moves to state 1 (a).

- Receives a data packet, its mode setting section is mode (II), and address car 4 is set. At this time, the station returns a response packet.

- Receive a data packet, and its mode setting section is mode (IV).

If the following conditions are met, it will remain in state 2.

- Receive a data packet, its mode setting part is mode (I), and Atto L and Su match. At this time, the station sends back a response packet, sets a timer to 2D, and waits for a data packet.

・Receive a data packet, and its mode setting section is the mode (薯). At this time, the station sets the timer to D and waits for a data packet.

If the following conditions are met, the process moves to state 3 (exit).

- A data packet is received, its mode setting section is mode (n), and the addresses do not match. At this time, the station sets the timer to 2D and waits for a data packet.

If the following conditions are met, move to state 4 (force).

- A data packet is received, its mode setting section is mode (1), and the addresses do not match. At this time, the station sets a timer to 3D and waits for a data packet or response back.

- A response packet was received. At this time, the station sets the timer to 3D and waits for a data packet or response packet.

■ If the station is in state 3.

If the following conditions are met, the state moves to state 1 (g).

- A response packet was received.

- Receive a data packet, 1, its mode setting section is mode (Il), and the addresses match. At this time, the station returns a response packet.

- Receive a data packet and its mode setting section is mode (+V).

If the following conditions are satisfied, the state moves to state 2, a Qo data packet is received, the mode setting part is mode (1), and the addresses match. At this time, the station sends back a response packet, sets a timer to 2D, and waits for a data packet.

- Receive a data packet and its mode setting section is mode (1). At this time, the station sets the timer to D and waits for a data packet.

If the following conditions are met, e→ remains in state W3. ...Receives a data packet, and its mode setting section is set to mode (II
) and the addresses do not match. At this time, the station sets the timer to 2D and waits for a data packet.

If the following conditions are met, move to state 4 (no.

- A data packet is received, its mode setting section is mode (1), and the addresses do not match. At this time, the station sets the timer to 3D and waits for a data packet or response packet.

■ If the station is in state 4.

If the following conditions are met, the state moves to state 1.

- Receive a data packet, its mode setting section is mode (It), and the addresses match. At this time, the station returns a response packet.

- Receive a data packet, and its mode setting section is mode (IV).

If the following conditions are met, it moves to state 2 (wa).

・A response message was received. At this time, the station (d) sets the timer to 2D and waits for a data packet.

- Receive a data packet, its mode setting part is mode (r), and the addresses match. At this time, the station sends back a response packet, sets a timer to 2D, and waits for a data packet.

- Receive a data packet and its mode setting section is mode (1). At this time, the station sets the timer to D and waits for a data packet.

If the following conditions are met, the station moves to state 3 (a hair/data packet is received, its mode setting part is mode CM>, and the addresses do not match. At this time, the station sets the timer to 2D and transfers the data wait for packet.

If the following conditions are met, it will remain in state 4).

- A data packet is received, its mode setting part is mode (1), and the addresses do not match. At this time, the station sets the timer to 3D and has a data packet or response packet.

The following table summarizes the conditions for (a) to (name).

Such state transition processing is performed by the mode setting circuit tr.

carried out by. FIG. 12 shows a block diagram of the mode setting circuit. The mode setting section information obtained from the decoder 6o through the 2-bit signal line 111 is held in a holding circuit 112, and the current state of the own station is held in a holding circuit 113. The signals obtained from the signal lines 114 and 115 indicating that the received data packet has not collided and that the frame inspection result indicates that the data packet is error-free are processed by the AND circuit 116, and
When the conditions are met, a rewritable signal is sent to the mode setting processing circuit 117 and the holding circuit 113 via the signal line 118. When the mode setting processing circuit 117 receives the rewritable signal, it obtains the current data packet sending control state from the 2-bit signal line 119, the contents of the mode setting section of the received data packet from the 2-bit signal line 120, and ′
The mode setting process is carried out according to the state transition diagram shown in FIG. The contents of the holding circuit 113 are transmitted to the CPU via a 2-bit signal line 122.
54, and the CPU 64 performs processing according to the communication mode of its own station according to the information.

Effects of the invention In this way, by changing the communication mode for each packet,
It can respond flexibly depending on the type of information and communicate efficiently.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the configuration of a conventional communication system, Fig. 2 is a diagram showing an example of the frame configuration of a data packet in the conventional communication system, and Fig. 3 is the configuration of a transmission/reception control unit of a station in the conventional communication system. Illustration showing an example, 4th
5 is a diagram showing an example of the frame structure of a data packet in the present invention, FIG. 5 is a diagram showing an example of correspondence between the communication mode and the mode setting section in the present invention, and FIG. FIG. 7 is a diagram showing the operation of the station in the communication mode in which a response packet is returned in the present invention, and FIG. 8 is a diagram showing the operation of the station in the communication mode in which a response packet is not returned in the present invention. FIG. 9 is a diagram showing the operation of the station in a communication mode in which communication is performed by sending back a response packet, and FIG.
FIG. 0 is a diagram showing an example of the configuration of the transmission/reception control unit of a station in the communication system according to the present invention, FIG. 11 is a diagram showing an example of a state transition diagram of the communication mode of each station according to the present invention, and FIG. FIG. 3 is a diagram showing an example of a block diagram of a mode setting drunkenness circuit. 110...mode setting circuit, i~ri/yama...state transition conditions. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 12

Claims (2)

[Claims] (1) In a system in which multiple stations are connected through a common transmission path and communicate with each other, when a station packetizes information and sends it out, a mode setting section is provided in the packet, and the communication mode is set in the mode setting section. setting, and other stations in the system set their own communication mode according to this mode setting section.
A communication system characterized by changing the communication mode for each packet. (2) The mode setting section has a mode in which no response packet is returned, a mode in which a response packet is returned, a mode in which communication is continued after communication without a response packet returned, and a mode in which communication is continued after communication in which a response packet is returned. Having a communication mode corresponding to the communication mode, and making the communication mode variable for each packet by having other stations in the system set the communication mode of their own station scene according to the mode setting section. A communication system according to claim 1, characterized in that: