JPS5846096B2 - Control method for local transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a local transmission system that allows the number of stations to be increased without reducing the data transmission rate.

Generally, in an in-plant transmission system such as an industrial plant, control computers, plant controls, process input/output, typewriters, character display man-machine interfaces, etc. are distributed over a range of several kilometers to several tens of kilometers. It is connected by several cables and performs bit-serial data transmission.

FIG. 1 is a block diagram showing a general local transmission system.

In the figure, 1 is a loop-shaped transmission line 2a to 2n are a plurality of transmitting/receiving stations connected to this transmission line 1;
3a to 3n are devices connected to the stations 2a to 2n, such as control computers, plant controllers, process input/output or machine interfaces such as typewriters and character displays, and 4 is a device for transmitting a predetermined fJ frame format to the transmission line 1 It is a central synchronization device that circulates in a fixed direction.

It was.

FIG. 2 is a diagram showing a conventional transmission frame format, where P is a synchronization signal for frame synchronization, and 81 to S
n is a plurality of time slots following this synchronization signal P.

The stations 2a to 2n have time slots 81 to Sn allocated to each station in advance.
It is used to transmit data.

Note that 5 indicates the frame format Matsudra.

Next, the operation of the conventional control method for the local area transmission system will be explained.

If n time slots S□ to Sn are assigned to n stations 2a to 2n, for example, when station 2m transmits data with station 2n, the transmission time slot fixed method is used. In the fixed reception time slot method, the time slot Sm is used, and in the fixed reception time slot method, the time slot Sn is used.

However, according to the conventional control method of the local area transmission system, time slots are required as many as the number of stations, and as the number of stations increases, the number of time slots increases and the frame circulation period, that is, the data transmission rate decreases.

Furthermore, low traffic stations also occupy one time slot, resulting in poor transmission efficiency.

Moreover, since each station transmits data without permission, the control of the transmission system becomes extremely complicated, making it unsuitable as a computer-intensive local transmission system.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned drawbacks, simplify the control of a transmission system through centralized control, and provide an efficient control system for a local transmission system.

To achieve this purpose, the present invention divides stations connected on a loop into master stations and slave stations, allocates data transmission/reception time slots and interrupt reception time slots only to the master station, and assigns time slots to the slave stations. By not assigning slots when they are fixed, it is possible to increase the number of slave stations without reducing the transmission speed.
This will be explained in detail below using examples.

FIG. 3 is a diagram showing a frame format driver on a transmission path used in the control method of the local transmission system according to the present invention.

In the figure, 6a-6bs6c... are the first main station to which the first computer connects, the second main station to which the second computer connects, and the third main station to which the third computer connects. The data transmission/reception time slots 7a, 7b, 7c, etc. assigned to the stations respectively are the interrupt reception time slots assigned to the first to third master stations, respectively, and these are the interrupt reception time slots assigned to multiple stations. As shown in FIG. 5, the interrupt reception time slots 7a, 7b, 7c, etc. are provided with control codes 8a,
It consists of information 8b indicating the cause of the interrupt, and a source station address 8c5 that is the source of the interrupt request.

Next, the control operation of the local transmission system according to the above configuration will be explained.

1. When transmitting data from the master station to the slave station, as shown in the data output sequence in Figure 4a, the master station, for example, the station to which the first computer is connected, is used for data transmission and reception. time slot)
6a is used to send the destination station address, then write command data, check code, and work code in sequence.

On the other hand, when the master station reads data from the slave station, the master station sends a command indicating the destination station and read, as shown in the data input sequence of FIG.

Therefore, when the slave station receives these signals, it sequentially sends out data, a check code, and an end code.

In one or more of these cases, the main station takes the initiative and performs data transmission.

1. Next, when a data transmission request occurs to the slave station, the interrupt receiving slot 7a assigned to the master station of the other party, for example, the station connected to the first computer, is used, and the interrupt shown in FIG. Submit information.

The master station that receives the interrupt uses the time slot for data transmission and reception assigned to itself and executes the data transmission sequence or data input sequence according to the cause of the interrupt.

As explained in detail above, according to the control method of the local transmission system according to the present invention, only the main station connected to a plurality of computers that control terminals connected to a loop-shaped transmission path Since time slots are given for data transmission and time slots for interrupt reception, and time slots are not given to slave stations to which terminals are connected, the number of time slots only needs to be the same as the number of master stations on the transmission path. The number of terminal stations can be increased without reducing speed.

Furthermore, since the slave station does not transmit or receive data without permission, and information is exchanged under the command of the computer connected to the master station, centralized control of the transmission system 75 is performed dynamically and is computer-intensive. This has the effect of realizing local transmission suitable for data exchange.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a general internal transmission system;
The figure shows a conventional transmission frame format, FIG. 3 shows a frame format on a transmission path used in the control method of the local transmission system according to the present invention, and FIG. 4a
4 is a diagram showing a data input/output sequence for explaining the operation of FIG. 3, and FIG. 5 is a diagram showing the format of an interrupt reception time slot used in FIG. 3. DESCRIPTION OF SYMBOLS 1... Transmission path, 2a-2n... Station for transmitting and receiving, 3a-3n... Equipment such as machine interface, 4... Central synchronization device, 5... Frame format, 6an, 6bb and 6c. ...Time slots for data transmission and reception, 7a, 7b and 7c...Time slots for interrupt reception, 8a...Control code, 8b...
Information indicating the cause of the interrupt, 8c... Source station address. In the figures, the same or corresponding parts are given the same reference numerals.

Claims (1)

[Claims] A loop-shaped transmission path for transmitting 1-bit serial data, a plurality of main stations connected to this transmission path and each having a data transmission/reception time slot p and an interrupt reception time slot assigned in advance, and a A plurality of connected slave stations to which time slots are not fixedly assigned, and a central synchronization system that circulates a frame format containing a plurality of data transmission/reception time slot buttons and interrupt reception time slots in a fixed direction on the transmission path. If the master station has the initiative, the master station 75 transmits the destination station address and command to the slave station of the other party using the data transmission/reception time slot assigned to the master station. After that, data transmission is performed with the slave station of the destination, and if a request for data transmission occurs to the slave station, the slave station receives the interrupt reception time slot assigned to the master station of the destination. , and in response to this transmits data transmission with the slave station where the data transmission request has occurred using the data transmission/reception time slot assigned to the receiving station of the destination master station. A control method for a local transmission system characterized by: