JPS60256252A - Cyclic transmission system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a cyclic data transmission system suitable for transmission of control signals for railway vehicles.

[Background of the invention]

In order to deal with the increase in the amount of information required to be transmitted due to the expansion of control and monitoring functions in trains, it is being considered to provide data transmission paths in trains and perform multiplex transmission.

That is, as shown in FIG. 1, a loop network has been proposed in which transmission stations 5TO-8T2 are provided within a train T and are connected in a loop through transmission lines. In the figure, MCI is a driver's cab, and future control outputs are transmitted to devices EQI and EQ2 via the network.

As a transmission method in this case, a fixed allocation cyclic transmission method has been proposed because the maximum transmission delay is constant, data is transmitted periodically, and reliability is high.

That is, the data frame in this case, as shown in FIG. 2, includes a header part H, a data part D, and an ending part E.
The data section is divided into D1 to D, and is also allocated to each station so that transmission from each transmission station other than the driver's cab is also possible. Each station repeatedly receives and transmits the entire frame of data, causing a set of bucket barrels (store-and-forward system) to circulate on a loop.

However, if the transmission operation of this method is plotted with one hour on the horizontal axis and the position of the transmission station on the vertical axis, it will be as shown in Figures (2) and 3, where the data cycle time (loop period) T
L is the reception time T, where n is the number of transmission stations.
, = transmission time T0 (ignoring 1" o+) In the case of cyclic transmission in which all stations access the frame, TI-kin(T0+TB)... (1) However, 1゛6: Each station The disadvantage is that the data processing time becomes significantly longer.

[Purpose of the invention]

An object of the present invention is to provide a cyclic transmission method with short data transmission time.

[Summary of the invention]

The key point of the present invention is that fixed allocation allows transmission with a small delay when a priority transmission request occurs, such as when there is a change in data in cyclic transmission, whereas when there is no priority transmission request, such as when there is no change in data. In this case, increase the transmission cycle.

[Embodiments of the invention]

FIG. 4 shows the configuration of a transmission station (3) according to an embodiment of the present invention. The transmission station includes a microprocessor MPU, random access memory RAM, read-only memory ROM, and data link controller DLC0,1.
, parallel interface PIF, tristate gate G
It is composed of first-in, first-out memories FIFO0 and FIFO1, and its operation is controlled by a program in ROM. The DLC performs serial/parallel conversion of data and controls transmission data in accordance with communication protocols (protocols).

FIFO is a buffer memory for transmission and reception, and PIF exchanges data with devices.

In this case, the frame used has a structure as shown in FIG. 5, and the data portion is different from FIG. 2 in that data for one station is allocated to one frame.

The transmission method in this case when no station has a priority transmission request is shown in FIG. Assuming that transmission station STO has the right to transmit at time t=O, then ST
O turns off Gl and turns on G2, and transmits the data in F I FOO to each station all at once. The other stations are 61 on and (4) 62 off. In this case, the circulated data is also received by the FIFO 1 at the STO. 0 Next, the STO has the transmission right (
Token TK) is sent. The token frame is, for example, as shown in FIG. 7, and has a partial area indicating that it is a token, and data of the station number NST from which the token should be received.

In normal times when there is no data change, the token's NS
The T designation is not continuous and is transmitted to every 0th station. That is, for example, in Fig. 8, every other STO→
ST2→ST4→STI→ST3→STO (if the total number of stations is even, discontinuity occurs, but the same applies).

These stations then transmit data frames. In this way, the period Ttl in which the token TK circulates is 1'L1 = TL 2, where the loop period of the method of passing the token to an adjacent station is TL 2.
...... (2).

(5) Here, if a priority transmission request occurs at a certain transmission station (fixed allocation is a change in data, etc.), as shown in the 9th operation explanatory diagram and the functional flowchart in Figure 10, after data reception is completed, Gate G1 of the transmission station hardware is turned off (step 30). In this way, no token is transmitted to stations downstream in the data flow. Therefore, check the value of the next transmitting station designation NST of the received token in this state, and if NST is smaller than the own station number, turn on G1 (step 60).
and waits for input of the next token (step 40).
Returning to the diagram, Sr1 receives the TKI, but since NST is 2, which is smaller than itself, Sr1 does not take the token and has Sr1 send it. Then, Sr1 receives TK2 that occurs after the data transmission is completed, and since N5T=4 here, it learns that NST>3 and forcibly occupies the token (step 70), and transmits frame F3 with priority (step 80). ), then generates N5T=4 tokens and S
Make r1 perform regular transmission. If we do this (6), the period of the token can be expressed by equation (2),
Since the speed can be increased and this can be caught and transmitted, a cyclic data transmission system can be obtained in which the response is quick when the control signal changes, and data is sent periodically even when there is no data change.

FIG. 11 shows another embodiment of the present invention applied to store-and-forward transmission using transmission rights. In this case, normally, as in the embodiment shown in FIG.
In Figure 1, after station O transmits, it transfers the transmission right from STI to S.
T2 and Sr2), and if a priority transmission request occurs at transmission station ST3, the transmission right is then transferred to Sr2.
2→ST3→Sr4 without transmitting, the station occupies the transmission right with Sr1, performs its own transmission, and then passes the transmission right to Sr4, which is the official scheduled occupier.

Such operations are performed by a microcomputer within the transmission station. That is, as shown in the flowchart of FIG. 12, each step (7) waits for the reception of a token (step 10), determines whether it is the token receiver's turn to transmit (step 20), and then sends the token in a predetermined order. If so, continue to occupy the token (step 40) and send the data (step 50).
), even if it is not your turn to transmit, it is determined whether there is a priority transmission request (step 30), and if there is, the token is forcibly occupied in this case (step 40), and the data is Send.

In this way, the period in which the token circulates is shortened, and moreover, the transmission station requesting priority transmission can reliably obtain the transmission right.

In the above embodiments, the shape of the network is a loop, but the present invention can also be applied to a bus shape or a star shape in addition to the loop shape.

In addition to this embodiment, an area for monitor data or a new area for transmitting packetized audio may be provided in the data frame since the maximum transmission delay time is guaranteed.

〔Effect of the invention〕

(8) According to the present invention, a cyclic transmission method is obtained in which the data transmission delay is small, the maximum transmission delay is below a certain value, the data is transmitted periodically, the reliability is high, and the data is suitable for control purposes. It will be done.

[Brief explanation of drawings]

Figure 1 is a conventional system diagram, Figures 2 and 3 are explanatory diagrams of a conventional embodiment, Figures 4 to 10 are explanatory diagrams of an embodiment of the present invention, and Figures 1I and 12. FIG. 3 is an explanatory diagram of another embodiment of the present invention. Gl, G2...tristate gate, D 1. ,
C.I. 2...Data link controller, FTFOI, 2...
...First-in first-out memory, PIF...Parallel interface, MPU...Microprocessor, RAM...
Random access memory, ROM...read only memory. Agent Patent Attorney Akio Takahashi (9) Invitation 1 Ryoki No. 50 Mo6 Fig. 7 Kasumikaku] A ■ - Fig. 8 Akira 9 Kasumi Haku 10

Claims (1)

[Claims] 1. When a data transmission line and a transmission station are set up to cyclically transmit fixed data, if there is no priority transmission request for the transmission station, the transmission right circulates between a series of said transmission stations, and the said transmission If the station receives a priority transmission request,
A cyclic transmission system characterized by comprising means for forcibly occupying the transmission right received by the transmission station and transmitting data.