JPH0119672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a data transmission method, and more particularly to a loop data transmission method in which each station sequentially transmits data in a broadcast mode of high-speed scan and low-speed scan based on instructions from a central management station.

b. Prior Art Conventionally, when each station uses a single loop-shaped transmission line in common in a time-division manner, there are fixed allocation methods and polling methods for determining a station that occupies a line.

The fixed allocation method is a method in which one frame is divided, each divided time slot is fixedly allocated to each station, and each station transmits its own data in its own slot. This method has the disadvantage that each station always occupies a certain amount of time on the line even when there is no data to be transmitted, so there are times when the line is not transmitting data, and the data transmission efficiency of the line is very poor.

On the other hand, the polling method is a method in which the line-occupying station is managed by a central management station (hereinafter referred to simply as the central station).
When the line becomes free, the central station sends a polling command to the transmission loop to search for slave stations requesting transmission.
When each slave station receives this polling command, the slave station that has data to transmit returns its own station name address and transmission priority level to the central station. The central station analyzes the transmission requests from each slave station during polling, determines the next line-occupying station in such a way that each station equally obtains the right to transmit, and attaches the line-occupying slave station name to the next select command. Send. The slave station that receives this exclusive slave station name obtains the right to transmit subsequent data, sends data to the line, and when the data transmission is completed, notifies the central station that the line is free with a completion command. In this polling method, the transmission of control commands such as poll commands, select commands, and completion commands frequently occupies the line.
It still has the disadvantage that the data transmission efficiency of the line deteriorates.

c. Purpose of the Invention The purpose of the present invention is to use the data transmission path effectively by immediately passing the transmission right to the next station when there is no data to be transmitted from the own station, and transmitting data so that the transmission data always occupies the transmission path. An object of the present invention is to provide a loop data transmission method that increases efficiency.

d. Structure of the Invention In order to achieve the above object, the present invention enables each slave station to transmit data in two modes: high-speed scan mode and low-speed scan mode.

In the high-speed scan mode, each slave station's transmission request is always serviced once within a fixed period, and is effective in cases where data transmission is required at fixed intervals or in highly urgent data transmission.

The high-speed scan transmission service of all slave stations ends within the above-mentioned fixed period, and the free time within the fixed period is used to transmit less urgent transmission data in the low-speed scan mode.

FIG. 1 is a schematic diagram of a data transmission system to which the loop data transmission method of the present invention is applied.
Central control station SVC and multiple (n) slave stations ST ₁ to _{ST o}
are connected in a loop through a single transmission path DL, and data is exchanged between them.

Figure 2 shows the central management station SVC (hereinafter simply referred to as SVC station) with the configuration shown in Figure 1 and a plurality of (n) slave stations ST ₁ to
FIG. ₂ is an operation timing diagram for explaining the operation of ST o (hereinafter simply referred to as ST ₁ to _{ST o} stations). In the figure, a indicates the time slot of each transmission frame based on the transmitting end of the SVC station. Figure c shows the status of the transmission frame transmitted from the SVC station, and d to g.
indicates the status of transmission frames transmitted from stations ST ₁ to _{ST o} with slight time delays. Figure b is
This shows a transmission frame transmitted from the ST _o station and received by the SVC station.

FIG. 3 is a detailed diagram of the above transmission frame, which is composed of [frame synchronization flag] + [command word] + [transmission station name] + [data].

e Effect of the Invention First, in the #1 frame time slot of Figure 2a, the SVC station transmits the #1 frame containing the command word of slow scan mode and transmission permission token to the ST1 station, as shown in Figure _2c . do. ST ₁ station detects the command word and determines whether there is data to be transmitted by its own station by low-speed scan, and if there is no data, the command word is not changed as shown in Figure 2 d.
Simply relay to ST ₂ stations. The ST ₂ station detects the command word, determines whether it has data to transmit by slow scan, and if so, changes the transmission permission token from to 〓 as shown in Figure 2 e, and sends the command word. , 〓, transmitting station name #2, and low-speed scan transmission data are placed on this #1 frame and transmitted to ST ₃ station. The ST ₃ station detects the command 〓, and its own station enters the relay mode, and simply relays the received frame and transmits it to the ST ₄ station, and at the same time stores it in its low-speed scan data reception memory for the #2 station. Below ST ₄ ~ _{ST o}
The station similarly detects the command 〓, stores the transmission data from the ST ₂ station in its low-speed scan data reception memory for station #2, and relays the frame signal to the downstream station. Transmission data from ST ₂ station relayed by ST _o station in Figure 2 g, 〓 #2 is the second
Arrive as shown in Figure b. The SVC station delays this received frame and continues to receive this frame as the #2 frame from the time when the #1 frame has been completely transmitted in the #1 frame time slot, as shown in Figure 2c.
ST ₁ relays the transmitted data frame from ST ₂ stations
Send to. At this time, the SVC station adds a command indicating that the low-speed scan is to be interrupted and sends it to the ST ₁ station. ST ₁ station detects the command word 〓 and sends #2 of own station
This frame is stored in the station's low-speed scan data reception memory and simultaneously relayed and transmitted to the ST ₂ station. In this way, the data broadcasted by the ST ₂ station is stored in the low-speed scan data reception memory for the #2 station of all stations other than the ST ₂ station.

Now, when the frame is received by ST ₂ station,
The ST ₂ station detects that the data it sent has completed its cycle, changes the command word of this frame to , and transmits it to the ST ₃ station. The ST ₃ station detects that the command is in this frame, and simply executes this command, even though the command word is .
ST Relay transmission to ₄ stations. (If there is no command, it will be in normal operation mode, and if ST ₃ station has low-speed transmission data, it will be a command, 〓, and the transmitting station name #3 and transmission data will be placed on this frame, but in this case, it is a command, so it is a command, , ) The ST ₃ station then detects the command, , and stores the slow scan transmission permission token to remember that the transmission right has been interrupted. Stations ST ₄ to _{ST o} similarly relay the command, , and store the low-speed scan transmission permission token at the same time as transmitting it to the downstream station.

When the SVC station finishes transmitting the #2 frame of the command, it interrupts the low-speed scan mode from the #3 frame time slot in Figure 2a, enters the high-speed scan mode, and starts the #3 frame as shown in Figure 2c.
Send a command like this to ST ₁ station. ST ₁ station detects the command, determines whether it has data to transmit by high-speed scanning, and if there is no data, it does not change the command as shown in Figure 2 (d).
ST Relay transmission to ₂ stations. ST ₂ detects the command, determines whether there is data to be transmitted by high-speed scanning, and if there is, changes the transmission permission token from 〓 to 〓 as shown in Figure 2 e, and sends the command 〓 and the transmitting station name. #2 and high-speed scan transmission data are placed on this frame and transmitted to ST ₃ station. Each station ST ₃ to _{ST 1} detects the command, enters the relay mode, and simply relays the received frame and transmits it to the downstream station, and at the same time stores it in the high-speed scan data reception memory for station #2. In this way, the high-speed scan transmission data broadcast from the ST ₂ station is stored in the high-speed scan data reception memory for station #2 of all stations.

Now, when the frame transmitted from the ST ₂ station comes around and is received by the ST ₂ station, the ST ₂ station changes the command word to , sends it to the ST ₃ station, and receives a transmission permission token. is passed to ST ₃ station. If the ST ₃ station has high-speed scan transmission data, the ST ₃ station will send the command,
〓 and transmit the transmitting station name #3 and transmit data on this frame. Broadcast transmission data from these _three ST stations goes around each station and is sent again.
Come back to ST ₃ station. During this round, the transmission data of ST ₃ is stored in the #3 high speed scan data reception memory of each station. Thereafter, in the same manner, the station that detects the transmission permission token sends high-speed scan transmission data, and all stations that receive this data store it in the high-speed scan data reception memory for that transmitting station.

In this way, the transmission permission token goes from ST ₄ to ST _o station, and finally the ST _o station sends the transmission permission token.
When the ST _o station sends a command to pass to the SVC station,
The SVC station detects this command, interrupts the high-speed scan mode in the #1' frame time slot as shown in _FIG . means polling mode, and is an instruction code for passing the low-speed scan mode transmission right to the station that was interrupted in the previous low-speed scan mode (resuming low-speed scan). The ST ₁ station detects that commands are present in this frame and simply relays these commands to the ST ₂ station even though they are commands (if there are no commands, it will be in normal operation mode and will send low-speed scan transmission data) If ST ₁ station has it, it is a command, and the transmitting station name #1 and low-speed scan transmission data are placed in this frame, but in this case it is a command, so it is a command, ,
to be relayed. ) ST ₂ station also sends the command ′,,
is simply relayed to ST ₃ stations. The ST ₃ station remembers that the right to transmit was interrupted in the #2 frame time slot as explained previously. Holds a slow scan transmission permission token. The ST ₃ station that has this token detects the command , , judges whether it has data that it wants to send in low-speed scan mode, and if so, changes the transmission permission token from 〓 to 〓 as shown in Figure 2 f. , imperative word,,〓
, transmitting station name #3 and low-speed scan transmission data are placed on this #1' frame and transmitted to ST ₄ station. (If there is no slow scan transmission data, the ST ₃ station simply relays the command, ) to the ST ₄ station, and uses the slow scan transmission permission token held by the ST ₄ station.
The ST ₄ stations will put their own transmission data on this #1′ frame. ) When the ST ₄ station detects the command,, Reset the send permission token.

Hereafter, ST ₅ to _{ST o} stations similarly detect the commands, , 〓, and simply relay and transmit this frame to the downstream station, and at the same time store it in their own station's low-speed scan data reception memory for station #3, and also store the previously stored low-speed scan data reception memory. Reset the slow scan transmission permission token. The #1' frame containing the transmission data from the ST ₃ station arrives from the ST _o station to the receiving end of the SVC station as shown in Figure 2b.
The SVC station delays this received frame, and from the time when the #1' frame has been completely transmitted from the SVC station in the #1' frame time slot, this received frame, , = #3 is sent as the #2' frame from the time when the # ₁ ' frame is completely transmitted from the SVC station. It is relayed to the station, but in this #2′ frame time slot.
The SVC station sends a normal low-speed scan mode frame with only the command code removed, #3, to the ST ₁ station. This #2' frame is relayed and transmitted by the ST ₁ station and the ST ₂ station, and is stored in the slow scan data reception memory for the #3 station of each own station. When the ST ₃ station receives this #2′ frame, it detects that its own transmission data has been broadcast to all stations, changes the command word of this frame to , and passes the low-speed scan transmission permission token to the downstream station. . ST ₄ stations or less downstream stations that have medium-low speed scan transmission data receive this token and switch to normal low speed scan mode for broadcast transmission, returning to the same mode as #1 frame time slot in the first explanation.

Now, in the timing diagram of Figure 2, SVC
The station operates to determine a high-speed scan mode and a low-speed scan mode, and the time from any high-speed scan mode to the next high-speed scan mode is set at regular intervals. During this fixed period, even if all the stations ( _ST1 station to _ST0 station) have high-speed scan transmission data, the time is set to be longer than the time required to transmit n frames so that all stations are served. To summarize the operation of the SVC station, it issues a command word for each frame at a fixed period, a command word for the next frame, and after that, when the receiving end of the SVC station receives the command word,...
It is only necessary to repeat the cyclic operation of outputting a command word to that frame when the above-mentioned fixed period has elapsed, and delaying the received frame and continuing to relay it to the next transmitted frame time slot. .

f Embodiment of the Invention FIG. 4 shows an embodiment of the configuration of a slave station according to the present invention.

When serial data having the format of one frame as shown in FIG. 3 is received as received data 1, the flag detector 2 detects the frame synchronization flag at the beginning of the frame and initializes the timing generator 3. The timing generator 3 outputs timing signals to the logic circuit 8 for determining the bit positions of the ~ time slot, SA time slot, and DA time slot shown in FIG. 3 every time a serial data bit arrives. First, when a command word is received at a time slot, it is stored in the flip-flop 4, and in the same manner, the command words, . These held command words are input to the logic circuit 8 as status signals, and the logic circuit 8 operates as follows depending on the combination of command words.

[] When a command word is received When a command word is received in the time slot, the logic circuit 8 determines whether the high-speed scan transmission request signal 18 issues a request for high-speed scan data transmission, and if there is a request, the logic circuit 8 The output "a" of the circuit 8 becomes "1" in this time slot, and the exclusive OR circuit (hereinafter referred to as EX-OR circuit) 10 inverts the received data and transmits it to the transmitted data 15 as a signal. Also, at this time, a transmission FF9 is set to remember that the own station is transmitting. In the next SA time slot, the output “b” of logic circuit 8 becomes “1” and own station name 12 is set.
It is transmitted through an AND circuit 11 and an OR circuit 14.
At this time, the AND circuit 21 is
Close the gate. In the next DA time slot, the output "d" of the logic circuit 8 becomes "1", and the transmission data of the local address part of the high-speed scan memory 17H of the common memory 17 is sent to the AND circuit 13 and the OR circuit.
It is transmitted through circuit 14. At this time, the gate of the AND circuit 21 is closed by the inverter 22.

Here, to summarize the configuration of the common memory 17,
In the memory 17, memory areas for each station are prepared for a high-speed scan memory 17H and a low-speed scan memory 17L, as shown in FIG. Memory areas containing data and other station numbers are allocated to high-speed scan data reception memory and low-speed scan data reception memory, which receive transmission data from other stations.

The contents of this memory 17 are exchanged with an external device via an interface (not shown), and after the own station transmission data is written in the memory 17,
A high-speed scan transmission request signal 18 or a low-speed scan transmission request signal 19 is issued. Further, the low-speed scan data reception memory in which the latest transmission data of all other stations is stored is read out via the interface.

Now, going back to the previous step, if the high-speed scan transmission request signal 18 does not issue a request, the output "a" of the logic circuit 8 becomes "0" at the time slot, and the received command word is relayed without being changed.
The relay mode is used in the subsequent SA and DA time slots, but the transmitted data in the SA and DA portions are ignored by downstream stations.

[] Command word when sending FF9 is reset, 〓
When the command word 〓 is received in the time slot,
The “a” output of the logic circuit 8 becomes “0”, the command word is relayed, and the subsequent serial data of the SA time slot and DA time slot are also transmitted.
EX-OR circuit 10, AND circuit 21, OR circuit 14
relayed through. At this time, the transmitting station name shown in Figure 3 is detected in the address register 16 in the SA time slot, the address register 16 specifies the address corresponding to the transmitting station name in the common memory 17, and the high-speed scan data is stored in the next DA time slot. is written into the high-speed scan memory 17H of the designated common memory 17.

[] When the transmitting FF9 receives the command word 〓 at the time of setting, reset the transmitting FF9 at the time slot,
At the same time, change the command word 〓 to 〓 and send it. SA,
The relay mode is used in the DA time slot, but the transmission of this part is meaningless to downstream stations.

[] When receiving the command word, performs the same operation as in [] with the command word changed to and high-speed scan changed to low-speed scan.

[] Command word when sending FF9 is reset, 〓
When receiving , the command word is changed to , high-speed scan is changed to low-speed scan, and the same operation as in [ ] is performed.

[] When the transmitting FF9 receives the command word 〓 when set, the command word is replaced and the same operation as in [] is performed.

[] When receiving the command word, , transmits the command word as it is in the time slot and sets the low-speed scan transmission permission token FF20. The subsequent SA and DA time slots are in relay mode, but this part is meaningless for downstream stations.

[] Command word when transmitting FF9 is reset.
When receiving 〓, the command word is transmitted as is in the time slot, and the serial data in the subsequent SA and DA time slots is relayed and transmitted. At this time, the transmitting station name is entered into the address register 16 at the SA time slot, and the low-speed scan data is written into the low-speed scan memory 17L specified by the address register 16 at the next DA time slot.

[] Command word when transmitting FF9 is set.
When receiving 〓, the inverted command word 〓 is transmitted in the time slot, and the transmitting FF9 is reset. SA,
The DA time slot operates in relay mode, but this part is meaningless for downstream stations.

[] When the token FF20 receives a command word, , at the time of reset, it transmits the command word as it is in the time slot.
The SA and DA time slots are in relay mode, but this part is meaningless for downstream stations.

[] When the token FF 20 receives a command word when it is set, if the command word is detected in the time slot and the low-speed scan transmission request signal 19 is issuing a request, the logic circuit 8 sets the output "a" to "1". The command word is inverted to 〓 and transmitted, the transmission FF9 is set, and the low-speed scan transmission permission token FF20 is reset. Transmit own station name 12 in the next SA time slot, and read common memory 17 in the DA time slot.
The data for local transmission from the low-speed scan memory 17L is transmitted through the AND circuit 13. Further, if the low-speed scan transmission request signal 19 does not issue a request, the command word is relayed as is and the low-speed scan transmission permission token FF20 is reset.
In the next SA and DA time slots, relay mode is used, but this part is meaningless for downstream stations.

[XII] When the command word ,,〓 is received, the command word 〓 is relayed as is in the time slot, the low-speed scan transmission permission token FF20 is reset, and the SA and DA time slots are thereafter transmitted in relay mode. At the same time, the transmitting station name of the SA time slot is entered into the address register 16, and the received data of the next DA time slot is written to the low-speed scan memory 17L of the common memory 17 specified by the address register 16.

g. Effects of the Invention According to the loop-shaped data transmission method of the present invention, all stations are always given one opportunity to transmit high-speed scan data in high-speed scan mode every fixed period. If not, the transmission right is immediately handed over to the next station, giving an opportunity to transmit the low-speed scan data in the low-speed scan mode, thereby providing a loop data transmission method with improved transmission efficiency.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of the loop data transmission method of the present invention, FIG. 2 is a timing diagram thereof, FIG. 3 is a detailed diagram of a transmission frame, and FIG. 4 is an embodiment of a slave station according to the present invention. This is a diagram. 1... Received data, 3... Timing generator,
8...Logic circuit, 9...Transmission FF, 12...
Local station name, 15...Transmission data, 16...Address register, 17...Common memory, 18...Transmission request, 19...Transmission request, 20...Token
FF.

Claims (1)

[Claims] 1. In a loop data transmission method in which a central management station and a plurality of slave stations are connected in a loop through a data transmission path and mutually exchange data, the central management station transmits data within a certain period. When a high-speed scan command for which a data transmission request is serviced is transmitted together with a transmission permission token, and a high-speed scan mode transmission permission token indicating that the high-speed scan transmission service of all slave stations has been completed is received, the free time within the above-mentioned fixed period A low-speed scan command to service low-priority data transmission requests is transmitted together with the transmission permission token, and when a predetermined time is reached, a low-speed scan interrupt command is transmitted, and each slave station receives the transmission frame transmitted from the upstream station. If the received signal of includes a transmission permission token, the local station transmits data corresponding to either the high speed scan mode or the slow scan mode to the downstream station in a transmission frame that does not include the transmission permission token, When the transmission frame is received by the own station after going around the loop, a transmission permission token is included in the transmission frame and transmitted to the downstream station, and when the received signal includes the low-speed scan interruption command, the transmission permission token is sent. Even if the transmission is received, the transmission is temporarily interrupted and the transmission permission token is held, and when the received signal includes the low-speed scan command, if the transmission permission token is held, the transmission that was once interrupted is resumed, and the transmission permission token is held. A loop data transmission method characterized in that when a received signal does not include a transmission permission token, the data of the transmission frame is stored in its own reception memory.