JPS625497B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a data transmission method that is effective for increasing line efficiency and transfer speed in data transmission devices connected in a loop.

FIG. 1 shows an example of the n-to-n communication method in conventional loop data transmission, and FIG. 2 shows the transmission data format. Data transmission device 1 as shown in the figure
-1 to 4 are connected in a ring to form a transmission system. One station from 1-1 to 4, for example, 1-1 as the master station M
The other stations 1-2 to 4 are slave stations S and have subordinate synchronization. Each station inserts and adds a destination address into a time slot previously assigned on the time axis and transmits data, while the receiver monitors the address inserted into this time slot and confirms that the own station address has been specified. If so, import the data and
Furthermore, the source of the data is known by the position of the time slot on the time axis.

As described above, in the conventional system, the time slot position dedicated to each station is fixed and fixed on the time axis, so the time slot assigned to a station that has no data to transmit has no information at all, resulting in poor transmission efficiency. Since the position on the time axis of the time slot into which transmission data can be inserted is fixed to one location in one frame, it is not suitable for high-speed transmission in stations where transmission data frequently occurs, as the next data cannot be sent unless the station waits for one frame. Disadvantages: Even if your own station has data that you want to send with priority over data sent by other stations, you cannot send the data with priority, so interactive transmission is not possible.Also, if the master station that controls the loop becomes an obstacle. The drawback was that data transmission was not possible at all.

In order to solve these drawbacks, the present invention eliminates the time slot, does not create a subordinate relationship of transmission rights such as parent and child among each station, and transmits a transmission permission command that is allowed to transmit data from itself to any other station. Only the station that has received the data from the station checks whether there is data to be transmitted from the own station, and if there is data to be transmitted, it transmits the data, and if there is no data to transmit and transfers the transmission right to another station, it sequentially transmits the above command to the other station. Transmission rights are delegated to each station, allowing them to send and receive data. In addition, a priority level indicating the transmission priority order is set for the data transmitted by each station, and all other stations add a response code to the data transmitted from the station with transmission rights with the transmission priority level of the transmission data of the own station. By returning this, the station that has the right to transmit knows the priority level of the transmission data of other stations, and by adding the highest level value among them to the command and transmitting it, the station that received the command To compare the level indicated by the command and the transmission data level of the own station, acquire the transmission right when the transmission level of the own station is equal or higher, and transmit the command as is to the next station when the transmission level of the own station is low. It is configured so that the transmission right can be freely transferred to the station with the highest priority level transmission data, and the data transmission order can be arbitrarily changed as necessary.This will be explained in detail below with reference to the drawings.

FIG. 3 is a block diagram showing an embodiment of a loop data transmission system to which the present invention is applied. Stations 3-1 to 3-4, which are equipped with various command detection and data transmission/reception functions, are connected to a loop transmission line 4. connected by. Figure 4 shows the format of each command and data, where a is the transmission permission command, b
is the transmitting station declaration command, c is the response code (affirmative),
d indicates a response code (negative), e indicates transmission data, and f indicates a link confirmation command. FIG. 5 is a time chart showing the data transmission and reception operations of each station.
In addition, ACK in Figure 4 is the ACK word, and NAK is the NAK.
The word CHK is an error detection word, EOT is an EOT word, and H, I, D, and L are codes for identifying each command.

Since no station has the right to transmit data when the power is turned on, the station that has the right to transmit data is first determined by the following method. If a transmission permission command is not received within a certain period of time after power is turned on, each station transmits a transmitting station declaration command to declare to other stations that it has the right to transmit. The transmitting station declaration command I consists of a command part and an index indicating the station code that sent the command. If two or more stations transmit the transmitting station declaration command at the same time, the station with the largest station code value will be given priority and sent first. obtain transmission rights. t ₁ in Figure 5
Station A corresponds to this, and at t ₀ , transmission declaration commands IA and IZ were sent from stations A and Z at the same time, but since (station A code) > (station Z code).
IZ is blocked from passing by station A, and IA goes around the loop and returns to station A. Station A further transmits the IA several times and after confirming that the IA is definitely returned, obtains the first transmission right. Station A, which has obtained the right to transmit, sends a link confirmation command LA to confirm the other station's readiness to receive data. Each station that receives LA uses acknowledgment codes A _B and A _C when it is ready to receive it.
~A _Z , and if the reception is not ready, negative acknowledgment codes N _B and N _C ~N _Z are transmitted. These response codes, as shown in FIG. 4, are composed of an ACK or NAK code and an index section in which the highest transmission data level value is set when the local station has transmission data. At t ₂ , when station A has received response codes from each station, it compares the transmission data level in each response code with its own transmission data level when it has data to transmit, and determines whether the transmission data level of its own station is the highest. Data is transmitted only when the level is high or at the same level.

Each station similarly returns response codes A _B , A _C to A _Z in response to the transmitted data DA from the A station. Station A uses the response code to check whether the transmitted data was correctly sent to the receiving station, and again compares each transmission data level in the response code with its own transmission data level, and determines whether the transmission data with a higher level is If it is in another station, the transmission level value is added to the index section of the transmission permission command and transmitted. A at t ₃
The station completes the transmission of data DA, appends the highest transmitted data level value included in the response code to the command, and transmits it.

When station B receives the transmission permission command HA sent by station A, it compares its own transmission data level with the transmission data level attached to the command, and if the transmission data level of its own station is high, it is the same as that of station A. However, when the transmitted data level of the own station is low, the command is sent as is to the C station.
In FIG. 5, since the transmitted data level of the B station is low at _t4 , the received command is transmitted to the C station.
Station C transmits its own data because its own transmit data level is higher than the transmit data level of the received command. After the transmission is completed, the C station again adds the highest transmission data level included in the response code to the command, and transmits the command to the D station. Thereafter, the commands are sequentially transmitted to the stations in a similar manner, and data is transferred between all stations.
Note that when there is no data to be transmitted to each station, the minimum value (=0) is added to the transmission data level in the command and response code.

If a station that has the right to transmit becomes disabled due to a power outage, etc., it will not be able to send or receive data for a while, but after a certain period of time, the transmitting station declaration command will be automatically sent between the remaining normal stations, so the right to transmit will be lost. A fight will take place and recovery will take place.

Note that E and e in FIG. 5 are codes indicating the end of each message and are used to determine the transmission timing of the response code of each station that does not have the transmission right.

FIG. 6 shows a station configuration for constructing an embodiment of a data communication system to which the method of the present invention shown in FIG. 3 is applied. In the figure, 18 is a timing controller that controls the method of the present invention, 17 is a command detection circuit, 19 is each command creation circuit, 16 is a reception data buffer, 20 is a transmission data buffer, 12
1 is a line adapter that passes the received signal RD to the transmitting side in the event of a power failure; 13 is a modulation/demodulation circuit; 14 is a line adapter that allows the received data RD to pass as is to the transmitting side, or creates each command using a transmission switching signal 15 from the timing controller 18 This is a transmission switching circuit that selects whether to send data from the circuit 19 or the transmission data buffer 20.

The timing controller 18 monitors each command detected by the command detection circuit 17, and when detecting a transmission permission command, determines whether or not there is transmission data stored in the transmission data buffer 20, the level of the transmission data, and the transmission data of the command. The levels are compared, and if the data level of the transmission data buffer 20 is high, it is sent out. When it is low, the command creation circuit 19 creates and transmits a command equivalent to the command.

The transmission switching circuit 14 selects and transmits either the received data RD or the data from the command generation circuit 19 or the transmission data buffer 20 according to the transmission switching signal 15 from the timing controller 18 during normal operation, but when there is a failure, the transmission switching circuit 14 selects and transmits the received data RD or the data from the command creation circuit 19 or the transmission data buffer 20. Pass all RDs to the sending side.

The parts indicated by capital letters IA, LA, AB, etc. in Fig. 5 are the command generation circuit 19 or the transmission data buffer 2.
Indicates data etc. sent from 0, lowercase letters ia,
La, ab, etc. indicate data passing from the receiving side to the transmitting side by the transmission switching circuit 14, or data input to the receiving data buffer 16, command detection circuit 17, etc.

With the above configuration, it is possible to adjust the transmission timing and send and receive data by moving the transmission right between each station connected by a loop-shaped transmission path, and it is possible to send and receive data as needed. By moving the transmission right to another station, the data transmission order can be changed between each station.

As explained above, the line efficiency is improved because the data transmission timing of each station is not fixed by time slots, etc., and the data transmission order of each station can be changed arbitrarily as needed, so the transfer speed can be increased. , it has the advantage of allowing interactive transmission.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional loop data transmission system, Fig. 2 is a conventional data format, Fig. 3 is a block diagram showing an embodiment of the data transmission system of the present invention, and Fig. 4 is a block diagram of the present invention. The data format of the invention system, FIG. 5 is a time chart of the invention system, and FIG. 6 is an example of the station configuration for configuring the system of FIG. 3. 1, 3... Data transmission device, 2... Transmission data format, 4... Transmission path, 5... Transmission permission command, 6... Transmitting station declaration command, 7... Acknowledgment code, 8... Negative response. Code, 9...Transmission data, 10...Link confirmation command, 11...End code, 12...Line adapter, 13...Modulation/demodulation circuit, 14...Transmission switching circuit, 15...Transmission switching signal, 16... Reception data buffer, 17...command detection circuit, 18...timing controller, 19...command creation circuit, 20...transmission data buffer.

Claims (1)

[Claims] 1. In a loop data transmission system in which n (n is plural) stations each equipped with a data transmission device are connected in a loop and each station communicates, each slave to transmission data from a control station with transmission rights is Means for adding a transmission priority level of data to be transmitted by the station to a response code of the station, and a control station receiving the response code transmitting a transmission permission command with a transmission priority level corresponding to the transmission priority level in the response code. and a dependent station receiving the transmission permission command acquires the transmission right and transmits the data if there is transmission data that is higher than the transmission priority level in the transmission permission command.