JPH03102936A - Multiple address communication system - Google Patents

Abstract

PURPOSE:To shorten the recovery time at the occurrence of an error by eliminating the need for waiting of a retransmission request for a long time from a slave station by a master station at the occurrence of the error and sending the retransmission data quickly. CONSTITUTION:Synchronization detecting circuits 1a, 2a use reception data 1ja, 2ja pull-in clock and frame synchronization in its own station and send a synchronization establishing signals 1m, 2m to timing generating circuits 1b, 2b when the synchronization is established. The circuits 1b, 2b use the signals 1m, 2m to give a required timing to each circuit in its own station to attain data processing in its own station. Frame detection circuits for its own station 1c, 2c detect a frame number from the reception data with frame number latch timing signals 1na, 2na given from the circuits 1b, 2b and give frame control enables signals 1l, 2l to frame control sections 1d, 2d when the frame number is a frame belonging to its own station.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for performing broadcast communication in a loop-type transmission system, the purpose of this method is to shorten the recovery time when an error occurs, and the master station and slave stations perform loop-type transmission. In a system that transfers data via a network, an error detection flag and a retransmission flag field are provided in the header of the frame, and an error flag detection unit that detects the error detection flag of the frame that has passed through each slave station, and a retransmission frame field. The master station is provided with a retransmission frame storage section that holds a retransmission frame, and a retransmission flag addition section that adds a retransmission flag to a retransmission frame when an error detection flag is detected. or an error frame reception control unit that prohibits the capture of a frame in which an error has been detected into its own station and instructs it to wait for retransmission; and a retransmission frame reception control unit that captures it into its own station when a retransmitted frame is received in a retransmission wait instruction state. This is achieved by providing an error flag adding section that adds an error detection flag to an error frame.

[Industrial Application Field] The present invention is applicable to loop type LAN (Local Area
The present invention relates to a system for carrying out broadcast communication in networks such as the Internet, and particularly relates to a system for broadcast communication that can shorten the recovery time when an error occurs.

As communications have become more reliable in recent years, recovery from data errors that occur during transmission is required.

Therefore, P − P (Point-to-Paint
) In the case of communication, when a receiving station detects a data error, it issues a retransmission request to the transmitting station and has the transmitting station retransmit normal data for the erroneous data, allowing only normal data to be sent. I am trying to receive it.

However, in the case of broadcast communication, since there are multiple receiving stations, it is necessary on the transmitting station (master station) side to identify from which slave station (receiving station) the retransmission request is from. Furthermore, when retransmitting data, it is necessary to retransmit data only to the slave stations that have not been able to receive normal data.

In this case, when an error occurs, there is no need for the master station to wait for a long time for a retransmission request from the slave station, and it is possible to quickly send retransmitted data, thereby shortening the recovery time when an error occurs. requested.

[Conventional technology]

In conventional loop-type LAN broadcast communication, even if a frame with a data error occurs after going around the loop and returns to the master station, it is difficult to determine which slave station received the frame at which the error occurred. , must wait for a retransmission request from the slave station. Furthermore, when retransmitting, it is necessary to retransmit even to slave stations that have successfully completed reception.

[Problem to be solved by the invention] Therefore, even if the slave station receives error data,
There is an inconvenience in that immediate recovery is not possible and it is necessary to wait for the result of recovery processing by the upper protocol.

The present invention is an attempt to solve the problems of the prior art, and eliminates the need for the master station to limit the slave stations to which data should be retransmitted in response to a data error in broadcast communication. By preventing the slave station from importing frames with data errors into its own station, error processing by the upper protocol can be reduced, and recovery in the event of an error is possible. The purpose is to shorten the time. [Means for Solving the Problems] As shown in the principle structure in FIG.
In a communication system that transmits and receives frames between a master station 1 and a slave station 2 to transfer data, an error detection flag indicating an error frame and a retransmission flag field indicating retransmitted data are added to the header of the frame for data transfer. establish.

The master station 1 is provided with an error flag detection section 1l, a retransmission frame storage section 12, and a retransmission flag adding section 13, and the slave station 2 is provided with an error detection section 2l, an error frame reception control section 22, and a retransmission frame storage section 12. A reception control section 23 and an error flag addition section 24 are provided.

The error flag detection section 11 provided in the master station 1 detects the error detection flag of the frame returned after going around each slave station, and the retransmission frame storage section 12 holds the data of the retransmission frame. .

Furthermore, the retransmission flag adding section 13 performs the function of adding a retransmission flag to the retransmission frame when the error detection flag is detected.

The error detection section 2l provided in the slave station 2 detects errors in frames on the transmission path, and the error frame reception control section 22 sends frames to which an error detection flag has been added or an error has been detected into the own station. It has the effect of prohibiting the incorporation of. Further, the retransmission frame reception control unit 23 takes the retransmission frame into its own station when it is received in the retransmission wait instruction state, and the error flag adding unit 24 adds an error detection flag to the frame in which an error has been detected. It is added.

[Effect]

FIGS. 2(a) to 2(j) are diagrams for explaining the operation of the present invention.

In each figure, 1 indicates a master station (transmission station), which transmits data in frames as the minimum unit. Numerals 2 to 4 are slave stations (receiving stations) that receive data from the master station, and slave stations 2, 3, and 4 receive the same data in this order. Is 5 a loop? A transmission line that exchanges data between stations. 6a and 6b indicate frames on the transmission path, each consisting of a frame header section (H) and a data (information) section (D). The frame header section stores a frame synchronization pattern (F) for performing frame synchronization, a transmitting station address, a receiving station address, a delimiter (management data), etc. (However, in Fig. 2, transmitting station address, receiving station address (delimiters etc. are omitted), data error detection flag (A), and retransmission flag indicating whether the data is normal data or retransmission data (
A field is provided in which R) is stored.

In the master station 1, when there is data (D1) to be transmitted after synchronization pull-in, for frames whose data error detection flag A in the frame header H is "0", the master station 1 carries the transmitted data D1 and also sets the retransmission flag R. r■, and is sent to the downstream side of the loop transmission line 5.

When a frame addressed to the slave station arrives, the slave stations 2 to 4 detect the presence or absence of a data error, and if no error occurs, the slave station takes in the data and promptly sends it to the downstream side.

When an error occurs, the data is not captured into the local station, the data error detection flag A is set to r1, and the data is sent downstream, and the frame waits for retransmission.

Furthermore, if the data error detection flag A has already been set in rlJ in the received frame, it will not be imported into the local station and will be in a state of waiting for a retransmission frame.

Also, the received frame is a retransmission frame (retransmission flag R = "
1) and if the local station is in the retransmission frame waiting state, the data is taken into the local station and the waiting state is released.

When the base station 1 receives a self-transmission frame with the data error detection flag A set, it transmits the same data again using the retransmission buffer.

In this way, in the present invention, as shown in FIG. 2(a) to 0),
The master station 1 retains the transmitted data in the retransmission buffer until the transmitted data returns to its own station in a normal state (that is, data error detection flag A = O), and all slave stations are in normal condition. This guarantees that you can receive the correct data.

In addition, when a slave station detects a frame error within its own station, or when it receives a frame in which a frame error has been detected by a slave station upstream from its own station (i.e., a frame with data error detection flag A = 1), prevents this frame from being imported into its own station, and enters a retransmission data wait state to ensure that only normal data is imported.

FIGS. 2(a) to 2(j) show an example of operation. Master station 1
teeth. When the own station detects a frame that can send data and confirms that the data error detection flag A of this frame is "0", it sends data Di to the slave station.

However, after the transmitted frame goes through the loop and is received again by the local station, the data Di is stored in the internal retransmission buffer until it is confirmed that the data error detection flag A is "O".
Please keep <. (Figure 2(a)).

After capturing the data DI, the slave station 2 transmits it to the downstream slave station (see FIG. 2).

Assume that a bit error occurs on the transmission path between slave station 2 and slave station 3 (FIG. 2(C)). The slave station 3 detects a data error in this frame, so it does not import it into its own station, and sets the data error detection flag A to "1".
It enters a state of waiting for a retransmitted frame (FIG. 2(d)). Here, W indicates a state of waiting for a retransmission frame. Note that any method such as CRC check, parity check, etc. may be used to detect data errors.

The next slave station 4 receives a frame with data error detection flag A of "1", so it does not unconditionally capture data and waits for a retransmitted frame (see Figure 2(e)).
).

In master station 1, the frame sent by itself has gone through the loop and returned, but when it learns that the data error detection flag A is rlJ, it sends the same data again from the retransmission buffer. . At this time, the data error detection flag A is set to "0" and the retransmission flag R is set to "1" (FIG. 2(f)).

Slave station 2 knows that this frame is a retransmission frame because the retransmission flag R is "1" even if it is a frame from master station I, and since it is not waiting for a retransmission frame, This frame is not captured and sent to the downstream slave station (FIG. 2(g)).

In order to receive the retransmitted frame while waiting for the retransmitted frame, the slave station 3 captures the data within itself and then transmits it to the downstream slave station (FIG. 2(h)). At this time, the state of waiting for retransmission frames is released.

The slave station 4 also performs the same operation as the slave station 3, and then transmits a frame to the downstream side (FIG. 2(i)).

Since the data error detection flag A has returned in the state of "0", the master station 1 judges that all the slave stations were able to receive the data DI in a normal state, and sends the next data (D2) to that frame. Pick it up and send it out. At this time, retransmission flag R
is set to "0" and data D2 is written in the retransmission buffer (FIG. 2 (j)).

〔Example〕

FIGS. 3(a) and 3(b) are diagrams showing an embodiment of the present invention, with FIG. 3(a) showing a master station and FIG. 3(b) showing a slave station. In each figure, the same parts as in FIG. 2 are indicated by the same numbers.

1a and 2a are synchronization detection circuits, which pull in clock synchronization and frame synchronization within their own station using received data lja and 2ja, respectively, and from the time when synchronization within their own station is established, timing detection circuits 1b and 2a, respectively. 2b, synchronization establishment signals 1m and 2m
Send out.

The timing control circuits 1b and 2b are circuits that provide necessary timing to each circuit within the own station using the same 3t11 establishment signals lm and 2m, and enable data processing within the own station. It is structured by etc.

1c and 2c are frame detection circuits for own station,
The frame number is detected from the received data by the frame number latch tie approval signals 1na and 2na given from the timing generation circuits 1b and 2b, and if the frame belongs to the own station, the frame control units 1d and 2d
, frame control permission signals ll and 2l are applied to the frame control permission signals ll and 2l. Note that the master station 1 uses the frame control permission signal 11 as a data selection signal, and does not transmit the transmission buffer side data 1v when the received frame cannot be used by the base station.

In FIG. 3(a), 1d is also a data control circuit, which monitors flags A and R in the frame belonging to its own station, and uses the monitoring results to send a transmission buffer selector control signal 1.
S is sent to the transmission bath sofa selector 1g.

1e is a transmission buffer circuit that buffers continuous data 1k from a transmission terminal station, etc., and transfers the transmission data It to a retransmission buffer circuit 1f and a transmission buffer selector 1g in frame units on a transmission path. conduct.

The retransmission buffer circuit If buffers the transmission buffer circuit output data 1t until the data transmitted on the transmission path returns in a normal state, that is, with the error detection flag A=0. The data sent on the transmission path is A=O
When it returns, the transmission buffer circuit sends 1t of data.
However, when it returns with A=1, it is transferred to the transmission buffer selector lg as retransmission data 1u.

Transmission buffer selector Ig selects transmission buffer circuit output data 1t or retransmission data 1u based on transmission buffer selector control signal is, and transfers it to data selector lh as transmission buffer side data 1v.

The data selector lh is instructed by a data select signal (or frame control permission signal) IN to select whether to transmit the received data lja as is or to transmit the transmission buffer side data 1v.
Alternatively, either the transmission buffer side data 1v is sent out as the transmission data ljb. At this time, when sending 1v of data on the transmission buffer side, error detection flag A=0
Send as. Further, in the case of transmitting the transmission buffer side data 1v, if the retransmission data 1u is selected, the retransmission flag R is set to 1, and if the transmission data it is selected, the retransmission flag is set to R=0 and then transmitted. The above flag operations are performed all at once by the transmission buffer selector 1g.

In addition, in FIG. 3 (b), 2d is also a data control circuit, and when it is instructed by the frame control permission signal 2Il that the received data 2ja is a frame belonging to the own station, that is, a frame that can be used by the own station. , flag A,
Control signals (2re, 2rf, 2rg) are sent to the buffer circuit 2e, the own status latch circuit 2f, and the error flag adding circuit 2g, respectively, based on R, the local status latch signal 2p, and the data error detection result. FIG. 4 shows the internal logic of the receiving side data control circuit.

The reception data error detection result in the reception data 2ja that is manually operated by the data control circuit 2d, the data error detection flag A, the retransmission flag R, and the local station status latch circuit 2f.
As shown in FIG. 4, the reception permission signal 2re, local station status signal 2rf, and error detection flag 2rg are determined as the output of the data control circuit 2d by the combination of each state with the status latch signal 2p from the terminal. . Here, "O" in the status latch signal 2p and the local station status signal 2rf indicates waiting for normal data, and "1" indicates waiting for retransmission data. Further, "0" in the reception permission signal 2re indicates reception is not permitted, and "1"
” indicates reception permission. “1” in the error detection flag addition signal 2rg indicates that the flag is not operated;
rlJ indicates that the flag is set to 1.

When the reception permission signal 2re becomes 1j, the reception data 2ja is temporarily accumulated in the reception buffer 2e and sent out as reception data 2k of the receiving terminal station.The local station status latch circuit 2f indicates that the local station is in a normal data waiting state. or waiting for retransmission data until the next frame belonging to the local station is received.Also, the error flag addition circuit 2g
sets the error detection flag A to "1" when an error is detected (that is, when 2rg=1). The data sent from the error flag addition circuit 2g is transferred to the downstream slave station or the master station as the slave station transmission data 2jb.

〔Effect of the invention〕

As explained above, according to the present invention, even if data with a data error is returned to the master station, there is no need for the master station to wait for a long time for a retransmission request from the slave station, and the data can be retransmitted immediately. You will be able to send it. This makes it possible to shorten the recovery time when an error occurs, which greatly contributes to increasing the reliability of loop-type LANs and the like to which the present invention is applied.

[Brief explanation of drawings]

Figure 1 is a diagram showing the principle structure of the present invention, Figure 2 (a) -
(j) is a diagram for explaining the action of the present invention, FIG.
4a) and 4(b) are diagrams showing one embodiment of the present invention, and FIG. 4 is a diagram showing the internal logic of the receiving side data control circuit. 1 is a master station, 2 is a slave station, 5 is a transmission path, 11 is an error flag detection section, 12 is a retransmission frame storage section, 13 is a retransmission flag addition section, 2l is an error detection section, 22 is an error frame reception control section, 23 is a retransmission frame reception control section, and 24 is an error flag adding section.

Claims (1)

[Claims] A master station (1) and a slave station (2) are connected in a loop via a transmission line (5), and frames are exchanged between the master station (1) and the slave station (2). In a system that transfers data by sending and receiving data, fields for an error detection flag indicating an error frame and a retransmission flag indicating retransmitted data are provided in the header part of the frame that transfers data, and the frame that has gone around each slave station and returned an error flag detection unit (11) that detects an error detection flag; a retransmission frame storage unit (12) that holds a retransmission frame; and a retransmission flag addition unit that adds the retransmission flag to the retransmission frame when the error detection flag is detected. A section (13) is provided in the master station (1), and an error detection section (
21), an error frame reception control unit (22) that prohibits the frame to which an error detection flag has been added or in which an error has been detected from being taken into its own station and instructs to wait for retransmission; A retransmission frame reception control unit (23) that captures a frame into its own station when the frame is received, and an error flag addition unit (24) that adds the error detection flag to the frame in which the error has been detected. Broadcast communication method.