JPS6282745A - Loop data transmission system - Google Patents

Abstract

PURPOSE:To attain data transmission with high efficiency and high reliability even to transmission line disturbance or reception station busy state by providing a field in which information whether or not requesting the sending of a reply code from a transmission state to a reception station is written to a frame so as to increase the utility of the transmission line. CONSTITUTION:The reception station 1 detects the logical level of a reply request flag F included in a frame FS sent from a transmission station 2 via a transmission line 3, and an affirmative reply code ACK is inserted in response to the logical level at the data reception or the frame FS is changed into an idle frame and the result is sent to the transmission line 3. When the data reception is disabled, a negative reply code NAK is inserted independently of the logical level of the reply request flag F and the result is sent to the transmission line 3. Thus, an unnecessary reply frame is less on the transmission line 3 and the transmission station side supervises the negative replay code NAK to apply retransmission control so as to attain quick correspondence and the data transmission with the high efficiency and high reliability is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a loop data transmission system that uses a loop-shaped transmission line to communicate between terminal stations.

[Conventional technology]

Conventionally, in this type of loop data transmission system, when transmitting data from an arbitrary transmitting station to a receiving station, the transmitting station detects empty frames among the frames circulating in the transmission path and A frame synchronization signal S, a destination address DA, a source address SA, data D, and an error check code CHK as shown in FIG. 4 were inserted into an empty frame and sent to the transmission path. - If the receiving station can receive this frame, it detects that the destination address DA is the same as its own address, extracts the data D, and at the same time sends an affirmative response code AK as shown in FIG. was inserted into the area occupied by data D and sent back to the transmitting station. If this frame cannot be received, a negative response code AK is inserted into the area occupied by data D and sent back to the transmitting station.

[Problem that the invention seeks to solve]

In the conventional loop data transmission method described above, - A frame occupied by a variable speed transmission station cannot be used until it goes around the transmission path and returns to the transmitting station, which reduces the usability of the transmission path, or in other words, the transmission efficiency. There is a drawback that it does. On the other hand, if the receiving station does not transmit affirmative or negative response information, recovery measures such as data retransmission from the transmitting station cannot be taken in the event of transmission path disturbance or the receiving station is busy, resulting in poor reliability. The disadvantage is that it decreases.

[Means for solving problems]

In order to eliminate such drawbacks, the present invention provides a field in the frame in which information indicating whether or not the transmitting station requests the receiving station to send a response code is provided in the frame. Detect field information from
If data cannot be received, a negative acknowledgment code is inserted into the frame and sent to the transmission path regardless of the field contents, and if data can be received and the field contents require a response, an acknowledgment code is extracted from the data. The frame is inserted into a later frame and sent to the transmission path, and when data can be received and the contents of the field do not require a response, the frame is sent out to the transmission path as an empty frame after data is extracted.

[Effect]

In the present invention, data retransmission can be performed quickly in response to transmission path disturbances, busy receiving stations, etc., and transmission efficiency does not decrease.

〔Example〕

First, an overview of an embodiment of the loop data transmission method according to the present invention will be explained. In this embodiment, conditions are set when the receiving station sends out an acknowledgment signal to notify that data has been received. That is, when transmitting a frame containing data from a transmitting station to a receiving station, a flag for requesting the above-mentioned response signal is added to the frame and sent. At this time, the flag is set to "1" when a response is required, and "0" when a response is not required, and is sent out.

On the other hand, on the receiving station side, the output of the flag detection unit that detects the logic of this flag is used to determine whether reception is possible, and if reception is not possible, a negative response code is added to the frame sent from the receiving station regardless of the logic of the flag. If the frame is receivable and the flag logic is "1", an acknowledgment code is added to the frame sent from the receiving station and sent; if it is receivable and the flag logic is rOJ, it is applicable. The frame is sent to the transmission path as an empty frame.

FIG. 1 shows a transmitting/receiving system to which an embodiment of the loop data transmission method according to the present invention is applied.

As shown in the figure, this system consists of a receiving station 1, a transmitting station 2, and so on. Transmission line 3. It consists of terminal 4.

FIG. 2 shows the sending frame FS sent from the transmitting station 2 to the receiving station 1, and FIG. 3 shows the sending frame FS sent from the receiving station 1 to the transmitting station 2.
This shows the format of the return frame FR sent back.

Next, the operation of this embodiment will be explained using FIGS. 1 to 3. In the receiving station 1, the code conversion circuit 11 is a circuit for receiving the signal from the loop-shaped transmission line 3, that is, the frame FS from the transmitting station 2, and transmitting the signal from the own station 1, that is, the frame FR. It is. The frame FS received through this code conversion circuit 11 is
Timing recovery circuit 12. Data receiving circuit 13. It is sent to each of the transmission frame creation circuits 14. The timing reproducing circuit 12 is a circuit for reproducing the reception timing of each signal within the frame FS. Data receiving circuit 13
receives the data D in the frame FS according to the timing signal from the timing recovery circuit 12, and extracts the data D. Data that cannot be received is sent from the code conversion circuit 11 to the transmission frame creation circuit 14.

Data F3 received by the data receiving circuit 13 is sent to the terminal 4 through the interface 18.

Further, the data receiving circuit 13 outputs a reception permission signal F3a indicating whether data can be received. If the data cannot be received, the reception permission signal F3a becomes "0", and if the data can be received, the reception permission signal F3a becomes "1". becomes. Reception availability signal F
When F3a is "1", the acknowledgment code sending circuit 16 outputs an acknowledgment code ACK, and when the reception permission signal F3a is "0", the negative acknowledgment code sending circuit 17 outputs a negative acknowledgment code NAK.

The flag detection circuit 15 detects the response request flag F from the received data F3 and determines the flag bit. If the bit is "1", it outputs a "1" signal and a "0" signal.
If so, the “0” signal is used as the judgment signal F5.
The frame is sent to the sending frame creation circuit 14 as a frame.

In the transmission frame creation circuit 14, the above-mentioned determination signal F5.
A return frame FR is created by processing the received frame F1 for the states of the three signals, the signal ACK and the signal NAK.

When the reception permission signal F3a is "0", a negative acknowledgment code NAK is inserted into the reception frame F1, and the code conversion circuit 1
1 to the transmission line 3. Reception availability signal F3a
is "1" and the determination signal F5 is "1", an acknowledgment code ACK is inserted into the received frame F1, and the received frame F1 is sent to the transmission path 3 via the code conversion circuit 11.

Further, when the reception permission signal F3a is "1" and the determination signal F5 is "0", the reception frame F1 is similarly sent to the transmission path 3 as an empty frame.

As described above, the receiving station 1 detects the logic level of the response request flag F included in the frame FS transmitted from the transmitting station 2 via the transmission path 3, and when receiving data, the logic level is set to Accordingly, an acknowledgment code ACK is inserted or the frame FS is made an empty frame and sent to the transmission path 3. Furthermore, when data cannot be received, a negative acknowledgment code is inserted regardless of the logic level of the response request flag F. NA
By inserting K and sending it to the transmission line 3 in the same way, unnecessary response frames on the transmission line 3 are reduced, and furthermore,
By monitoring the negative acknowledgment code NAK on the transmitting station side and performing retransmission control, it is possible to respond quickly and efficiently.
Highly reliable data transmission can be achieved.

〔Effect of the invention〕

As explained above, the present invention detects field information from a frame sent from a transmitting station, and if data cannot be received, a negative acknowledgment code is inserted into the frame regardless of the field contents, and the transmission path is transmitted. If data can be received and the field contents require a response, an acknowledgment code is inserted into the frame after data extraction and the frame is sent to the transmission path, and data can be received and the field contents require a response. If not, by sending the frame as an empty frame to the transmission path after data extraction, unnecessary response frames are reduced on the transmission path, and by monitoring the negative acknowledgment code at the transmitting station and performing retransmission control, etc. Since this becomes possible, it is possible to increase the usability of the transmission path, and at the same time, it is possible to perform efficient and reliable data transmission even when the transmission path is disturbed or the receiving station is busy.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a transmitting/receiving system to which an embodiment of the loop data transmission method according to the present invention is applied, and FIGS. 2 and 3 show sending frames and return frames used in this transmitting/receiving system. Data structure diagrams FIGS. 4 and 5 are data structure diagrams showing conventional sending frames and return frames. DESCRIPTION OF SYMBOLS 1... Receiving station, 2... Transmitting station, 3... Transmission path, 4... Terminal, 11... Code conversion circuit, 12
...Timing regeneration circuit, 13...Data reception circuit, 14...Transmission frame creation circuit, 15...
-Flag detection circuit, 16...Acknowledgement code sending circuit, 17...Negative response code sending circuit, 18...Interface.

Claims (1)

[Claims] A transmitting station and a receiving station are connected to a loop-shaped transmission path, and the receiving station receives a frame with data from the transmitting station, extracts data from this frame, inserts a response code, and transmits the data to the transmitting station. In a loop data transmission method in which data is transmitted and received by sending back data, a field is provided in the frame in which information indicating whether or not the transmitting station requests the receiving station to send the response code is written, The information in the field is detected from the frame sent from the transmitting station, and if the data cannot be received, a negative acknowledgment code is inserted into the frame regardless of the contents of the field and sent to the transmission path, and the data is received. If possible and the contents of the field require a response, insert an acknowledgment code into the frame after data extraction and send it to the transmission path, and if the data can be received and the contents of the field require a response. A loop data transmission method characterized in that when there is no data, the frame is sent to a transmission path as an empty frame after data extraction.