JPH0736559B2 - Multi-frame communication device for loop communication system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a token passing communication system, and more particularly to a multiframe communication for a loop communication system suitable for a token ring local area network (LAN). Regarding the device.

[Conventional technology]

In recent years, a LAN for transmitting data between a plurality of terminal devices on the premises has attracted attention. As one of this LAN,
There is a token ring system in which each terminal device is connected to a loop-shaped transmission line to form a loop communication system and a token is circulated on the loop transmission line. The standardization of the token ring control method is being promoted by the US IEEE 802 Committee, and the Draft IEEE Standard802.5 “Token Ring Acces
s Method "and Draft IEEE Standard 802.2“ Logical Lin
"k Control" refers to the format of frames for handling data.

By the way, when transmitting data between terminal devices connected to the loop transmission line, when the frame length at the time of transmission is limited, or when transmitting to a plurality of terminal devices at a time, the source terminal device is When acquiring the token that is the transmission right, multiple frames are transmitted at one time. Then, the terminal device receiving the frame acquires the token when it comes and sends the fact that the frame has been received to the transmission source.

[Problems to be solved by the invention]

However, in the above token ring system, when the destination cannot properly receive the frame sent by the transmission source, the frame is retransmitted slowly. In other words, in the conventional token ring method, when an abnormality occurs due to noise or the like, and one of the multiple frames transmitted by the transmission source is not normally received by the reception source, the reception source acquires a token and transmits it. Originally, a response indicating whether or not the frame is normally received is transmitted, and the source of the frame can know that the frame is not normally received only after receiving the response. Then, when the sender retransmits the frame,
The sender must get the next token. Therefore, in order to retransmit a frame, the transmission source and the transmission source must obtain tokens from each other, and it takes time before the frame is retransmitted, and communication efficiency decreases.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a multi-frame communication device capable of shortening the time until a frame is retransmitted.

[Means for solving problems]

A multi-frame communication device for a loop communication system according to the present invention includes a transmission control unit that creates a frame based on data to be transmitted, and a sequence number that adds a sequence number for identifying the frame created by the transmission control unit. A generation unit; a transmitter that sends the frame created by the transmission control unit to a loop transmission line; a receiver that receives the frame that is sent by the transmitter and has gone around the loop transmission line; And a frame detector for reading out the contents including the sequence number of the frame received by the receiver when the device continuously transmits a plurality of the frames, The sequence numbers of the frames detected by the detection unit are compared with the sequence numbers of the frames stored in the storage unit, and all the frames transmitted to the loop transmission line are compared. And having a frame abnormality detector for outputting a retransmission command frame at least unmatched sequence number when the both do not match the frame.

Further, the multi-frame communication device for loop communication system of the present invention, a transmission control unit that creates a frame based on the data to be transmitted, a transmitter that sends the frame created by the transmission control unit to the loop transmission path, A receiver that receives the frame transmitted by the transmitter and has passed through the loop transmission path, and a storage unit that stores the number of transmitted frames when the transmitter continuously transmits the plurality of frames. And a frame number counting unit for counting the number of frames received by the receiver, and the count content of the frame number counting unit and the storage content of the storage unit are compared. And a frame abnormality detector for detecting.

[Action]

In the present invention configured as described above, since the transmission source that continuously sends out a frame detects an abnormality in the frame and retransmits the frame without waiting for the response from the reception source, the frame retransmission time can be greatly reduced. The communication efficiency of the loop communication system can be improved.

〔Example〕

A preferred embodiment of a multi-frame communication device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows a schematic configuration of a loop communication system to which the multi-frame communication device according to the present invention is applied.

In FIG. 2, the communication devices 10, 20, 30, 40 are connected to the terminal devices 12, 22, 32, 42 via a bus, and are also connected to each other via a loop transmission line 50. .
Each of the communication devices 10, 20, 30, 40 has the same structure, and is similar to the communication device 10 shown in FIG.

The communication device 10 has a receiver 101 which is a receiver, and the receiver 101 receives a token or a frame (to be collectively referred to as a packet hereinafter) which will be described later and enters from a receiving end 103. The receiver 101 inputs the received packet to the shift registers 105 and 107. The packet input to the shift register 105 is transmitted from the transmission end 111 to the next communication device by the driver 109 which is a transmitter.

The shift register 107 converts the serial data in the packet into parallel data, and transfers the token detection circuit 115, the sequence number extraction circuit 117, the address extraction circuit 119, and the reception via the bus 113.
It is sent to the FIFO 121. When the token detection circuit 115 detects that the packet is a token, it outputs that fact to the transmission control unit 123.

The sequence number extraction circuit 117 functions as a frame detection unit, detects a frame sequence number 125 described later,
It is input to the frame abnormality detection circuit 127. The frame abnormality detection circuit 127 has a storage unit whose details will be described later, and stores the sequence number 131 assigned to each frame by the sequence number generation unit 129 when a plurality of frames are continuously transmitted.

The address extraction circuit 119 detects the transmission source of the received frame and inputs it to the comparator 133. The comparator 133 compares the value of the source address register 135 with a match signal 137 described later.
Is output to the frame abnormality detector 127. The transmission source address register 135 has the preset communication device 1
The source address of 0 is stored.

When the received frame is addressed to the terminal device 12, the reception FIFO 121 sends the frame to the reception buffer memory 139. The reception buffer memory 139 is controlled by the reception buffer memory control unit 141 and gives the data in the frame to the terminal device 12 via the bus 143.

When there is a transmission request from the terminal device 12, the data to be transmitted is input to the transmission buffer memory 145, and the terminal device 12 is made to wait until the token is received. This transmission buffer memory 14
5 is controlled by the transmission buffer memory control unit 147, and the set data is sent to the shift register 151 via the transmission FIFO 149. Also, the shift register 151 is connected with a sequence number generation unit 129, a delimiter generation unit 153, and a token generation unit 155 via a bus.

The transmission control unit 123 is the transmission buffer memory control unit 1
The control signal of 47 is input, and based on this control signal, the transmission data in the transmission buffer memory 145 is taken out to form a frame, which is input to the driver 109 via the shift register 151 and the driver 109 is operated. In addition, the transmission control unit 123, when sending out the last frame, activates the loop monitoring timer 157. The output of the loop monitoring timer 157 is input to the transmission buffer memory control unit 147 together with the output value 159 of the frame abnormality detector 127.

Multiframe communication by the communication system configured as described above is performed as follows.

For example, when the terminal device 12 requests the transmission of data, the data to be transmitted is set in the transmission buffer memory 145 via the bus 143, and the talk which is the transmission right circulating in the loop transmission line 50 is received. wait. The receiver 101 moves from the receiving end 103 to the token 161 as shown in the upper part of FIG.
When this token is received, the token 161 is input to the token detection circuit 115 via the cyst register 107 and detected.
When the token detection circuit 115 detects the token 161, it gives an activation signal for the transmission control unit 123 to the transmission control unit 123.

Upon receiving the activation signal, the transmission control unit 123 drives the transmission buffer memory control unit 147 to extract the transmission data set in the transmission buffer memory 145, and the delimiter generation unit 15
Create a frame and shift register 1 with 3 outputs
Enter in 51. When there are a plurality of frames to be transmitted at one time, the sequence number generation unit 129 assigns sequence numbers 1, 2, 3, ...
Sent to. The transmission control section 123 sends each frame F _{1 to} F ₄ in the shift register 151 to the loop transmission line 50 via the transmission end 111 by the driver 109 as shown in the lower part of FIG. release. Then, the transmission control unit 123, when transmitting the last frame (for example, F ₄ ),
The loop monitoring timer 157 is activated to measure the time when the frame F ₄ makes a loop and returns.

The frame created by the transmission control unit 123 has a format as shown in FIG. 4, for example. That is, the start delimiter SD is added to the beginning of the frame F to indicate the start point of the frame F. After the start delimiter SD, a control unit C, a destination (reception destination) address DA, and a transmission source address SA are provided. The sequence number portion SEQ is located next to the source address SA. The sequence number part SEQ is composed of, for example, 4 bits, and the sequence number generation part 129 sequentially assigns numbers in the transmission order.

Next to the sequence number part SEQ is an information part INF that stores data to be transmitted, then a frame check sequence part FCS, and finally an end delimiter ED indicating the end of the frame.

Each frame transmitted by the driver 109 goes around the loop transmission line 50, and as shown in the upper part of FIG.
After reaching 103, it is received by the receiver 101, converted into parallel data, and input to the sequence number extraction circuit 117 and the address extraction circuit 119. The address extraction circuit 119 extracts the address number in the source address portion SA of the frame F and sends it to the comparator 133. The comparator 133 compares the address number of the communication device 10 set in the source address register 135 in advance with the source address number fetched by the address extraction circuit 119, and when they match each other, a match signal 137. Is output to the frame abnormality detector 127.

The sequence number extraction circuit 117 reads out the sequence number 125 recorded in the sequence number portion SEQ which is a part of the content of the frame F and inputs it to the frame abnormality detector 127. Upon receiving the coincidence signal 137, the frame abnormality detector 127 compares the sequence number 125 read by the sequence number extraction circuit 117 with the sequence number 131 at the time of frame transmission stored in advance.

The frame abnormality detector 127 has a configuration as shown in FIG. The frame abnormality detection circuit 127 has a 4-bit sequence number 1 attached to the frame F by the sequence number generation unit 129.
31 is changed to 16 bits by the decoder 163, and the sequence numbers transmitted by the frames are stored in the flip-flops 165a to 165n provided corresponding to the sequence numbers. The sequence number 125 read by the sequence number extraction circuit 117 is
It is input to the decoder 167, corrected to 16 bits, and input to the AND circuit 169. Also, this AND circuit 169 has
The match signal 137 from the comparator 133 is input, and when the signal from the decoder 167 and the match signal 137 are input, the flip-flop 165 corresponding to the sequence number 125 is input.
Reset.

After the transmission control unit 123 transmits the last frame and activates the round-trip monitoring timer 157, it does not return even when it is time for the frame to loop back, and the flip-flops 165a to 165n shown in FIG. When any one of them is in the set state, the frame number corresponding to the flip-flop in the set state is converted into 4 bits by the encoder 171 and the output value 159 is sent to the transmission buffer memory control unit 1.
Entered in 47. Transmission buffer memory control unit 147, for example, as shown in FIG. 3 (A) the upper, third frame F ₃
If is disappeared due to noise or the like, the fact is input to the transmission control unit 123. When the next tone 161 is acquired, as shown in the upper part of FIG. 3 (B), the transmission control unit 123, in the missing frame F ₃ as shown in the lower part of FIG. 3 (B), is the same as in the first transmission. Is sent to the loop transmission line 50 and the token 161 is sent. The retransmitted frame F ₃ is received as described above as shown in the upper part of FIG. 3 (B), and the flip-flop as set in FIG. 5 is reset.

As described above, in this embodiment, since it is detected that an abnormality has occurred in the frame received by the transmission source and the frame in which the abnormality has occurred is retransmitted, it is not necessary to perform communication between the transmission source and the reception source. It is possible to significantly reduce the retransmission time. As a result, the communication efficiency in the loop communication system can be improved.

FIG. 6 is an explanatory diagram showing an embodiment of another retransmission method.
In the case of the present embodiment, when transmitting the frames F _{1 to} F ₄ for the _first time, the token is held without being transmitted, and after all the transmitted frames are returned, or the missing frames
After retransmitting F ₃ , the token 161 is detected. In the case of the present embodiment, other communication devices cannot transmit until the frame comes back, but when an abnormality occurs in the frame, the frame can be retransmitted without having a token.

As another frame retransmitting method, when an abnormality is detected in a frame that has looped back through the loop transmission line 50, there is also a method of retransmitting all the frames after the frame in which the abnormality is first detected. If any of the transmitted frames is abnormal, all the frames may be retransmitted. In this case, it is not necessary to give a sequence number to the frames, and it is sufficient to compare the number of received frames with the number of returned frames. In such a case, there is no need to select a specific frame at the time of retransmission, and the device can be simplified.

Although the frame has not disappeared, if an abnormality occurs in the content of the frame, the receiving end sets the end limit ED of the frame to "1", and the transmitting end detects this and retransmits the frame. It is also possible. In the above embodiment, the case where the sequence number part SEQ of the frame F is provided next to the source address part SA has been described.
It may be in another position.

〔The invention's effect〕

As described above, according to the present invention, since the frame source detects the frame abnormality and retransmits the frame, the time until the frame is retransmitted can be significantly shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a multi-frame communication device according to the present invention, FIG. 2 is an explanatory diagram of a loop communication system to which the communication device shown in FIG. 1 is applied, and FIG. FIG. 4 is an explanatory diagram showing an example of a frame retransmission procedure by the communication device shown in FIG. 4, FIG. 4 is an explanatory diagram showing an example of a frame format, and FIG. 5 is a frame abnormality detector of the communication device shown in FIG. FIG. 6 is an explanatory diagram of another embodiment of the frame retransmission procedure. 10,20,30,40 …… communication device, 12,22,32,42 …… terminal device,
50: loop transmission line, 101: receiver, 109: driver, 117: sequence number extraction circuit, 119 ... address extraction circuit, 123 ... transmission control unit, 127 ... frame abnormality detector,
129 ...... sequence number generation unit, 133 ...... comparator, 157 ...... round monitoring timer, 161 ...... token, 165A～165n ...... flip-flops, F, F ₁ to F ₄ ...... frame.

Claims (2)

[Claims] 1. A transmission control unit that creates a frame based on data to be transmitted, a sequence number generation unit that adds a sequence number for identifying the frame created by the transmission control unit, and the transmission control unit. A transmitter for transmitting the frame created by the above to a loop transmission line, a receiver for transmitting the frame transmitted by the transmitter and receiving the frame that has made a round in the loop transmission line, and a transmitter for continuously transmitting a plurality of the frames. Storage unit that stores the sequence number of each frame, the frame detection unit that reads out the contents including the sequence number of the frame received by the receiver, and the frame detected by the frame detection unit. The sequence number and the sequence number of each frame stored in the storage unit were compared, and both did not match for all the frames transmitted to the loop transmission line. Multiframe communication device for loop communication system, comprising a frame abnormality detector for outputting a retransmission command frame at least unmatched sequence number, to come. 2. A transmission control unit that creates a frame based on data to be transmitted, a transmitter that sends the frame created by the transmission control unit to a loop transmission path, and a transmitter that sends the frame to the loop. A receiver that receives the frame that has passed through a transmission path, a storage unit that stores the number of transmitted frames when the transmitter continuously transmits the plurality of frames, and a frame that the receiver receives A frame number counting section for counting the number, a frame abnormality detector for comparing the count content of the frame number counting section and the stored content of the storage section, and detecting the frame abnormality when the two do not match, A multi-frame communication device for a loop communication system, comprising: