JPH0433180B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention provides loop data transmission in which a main station (also referred to as a center device) that controls communication and a plurality of terminal stations (also referred to as terminals) are sequentially connected via a loop-shaped transmission path (also simply referred to as a loop). The present invention relates to a device for preventing transmission data from a station from going around the loop more than once and causing a reception error in a system (also called a loop transmission system).

[Prior art and its problems]

In this type of loop data transmission system, each station (center device or multiple terminals) connected on the loop bypass-transmits data received from a receiving terminal to an adjacent station via a transmitting terminal. By sequentially transmitting data to the next station, the data is sent and received as it goes around the loop once. In addition, in loop transmission, once the transmitted data goes around the loop more than once, it overlaps with the data of the next transmitting station, resulting in a thumb check error or an increase in the number of transmitted characters, resulting in a transmission error. There is a problem. Therefore, in order to prevent the same data from going around the loop more than once, the station transmitting data receives the data that comes back after going around the loop once, and then transmits the data itself. If it is data, it must be controlled so that it is not bypassed to the next station. However, if the microcomputer within the device controls the process of returning the data to the loop while determining whether the received data is the data that was sent by the device itself, this places a burden on the transmission control software. Furthermore, since data is transferred in this manner, there are problems in that the ability to perform other tasks is reduced and transmission delays occur. To solve this problem, at the same time as sending data, set a timer value that assumes the time it takes for the sent data to return after going around the loop once (referred to as one round transmission time), and set the timer value to After that, there are ways to stop bypassing the received data. However, in this method, since the number of terminals constituting the transmission loop and the distance of the transmission path vary depending on the system, it is necessary to measure the transmission time for one round of the loop and set the timer value for each system. Further, there is a problem in that the timer value must be changed each time the number of terminals or the distance of the transmission path changes due to changes in the system. Therefore, there is a method of fixing the timer value to the one round transmission time assuming the maximum scale of the system, but
Since other terminals cannot send data until the timer value expires, this will cause loop 1.
Even in a system with a short transmission time, a problem arises in that the overall transmission time is delayed as a result.

[Purpose of the invention]

The present invention eliminates the above-mentioned problems in a loop data transmission system, reduces the burden on software at a data transmitting station to check whether data on the loop returns, and
It is an object of the present invention to provide a transmission error prevention device that does not require the trouble of manually measuring the transmission time for one round of a loop or setting timer values, and can minimize transmission delays.

[Key points of the invention]

The key point of this invention is that the main station loops in a predetermined condition in advance, such as when the power is turned on to the main station or when the loop transmission path returns to a normal loop state from a disconnected state due to disconnection or disconnection of a connector. The main station performs special communication to measure the one-round transmission time, creates one-round transmission time data, and then
During normal communication with a terminal, the previously created one-round transmission time data is included in the communication data sent to the terminal and sent to all terminals, so that each station on the loop knows this one-round transmission time. Based on the data, when in transmit mode, we set a data bypass prohibition period until switching to receive bypass mode, and on the other hand, when entering transmit mode from receive bypass mode, we enter transmit mode after receiving the transmit data from another station. The key point is that the timing of the transmission operation is optimized by determining the time until the end of the transmission. In other words, the main point of the present invention is that a main station that controls transmission, a plurality of terminal stations, and each of the above stations are sequentially connected in a loop, and that each station is equipped with a transmission line that transmits data in a predetermined direction. can receive data via an adjacent station on the receiving side of the transmission path, and when in reception bypass mode, further bypass-transmits this received data as it is to an adjacent station on the transmission side of the transmission path,
Furthermore, when in the transmission mode, data is transmitted to the adjacent station on the sending side, and data transmission is performed by cutting off the bypass during this time, so that at least the main station communicates data with each terminal station. In a loop transmission system, the main station is equipped with a
(when detecting loop breakage recovery, etc.), all terminals are kept in reception bypass mode, and predetermined time measurement data (data for measuring one round transmission time, etc.) is transmitted to the adjacent station on the transmitting side. After this transmission, a means (a microcomputer, a timer for measuring one round transmission time, etc.) for measuring one round transmission time until the time measurement data which has made one round of the transmission line is received from the adjacent station on the receiving side, means (such as a microcomputer) for transmitting a predetermined waiting time (such as one-round transmission time data) including at least this time to all terminal stations based on this measurement;
and a means (such as a microcomputer) provided in each station for maintaining the transmission mode until the waiting time has elapsed after the station has finished transmitting, and then switching to the reception bypass mode. It is in.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on FIGS. 1 to 5. FIG. 1 is a time chart explaining the operation of the main part of the main station as an embodiment of the present invention, FIG. 2 is a diagram showing the transmission format of communication between the main station and the terminal, and FIG. Similarly, block diagram 4 shows the configuration of the loop transmission control circuit in each station.
This figure similarly shows the structure of data for measuring one round transmission time transmitted by the main station, and FIG. 5 is a block diagram similarly showing the structure of the loop type transmission system. In each figure, the same reference numerals indicate the same or corresponding parts. Also, the signal level “High”, “Low”
are simply written as H and L. FIG. 5 is a schematic diagram of the loop data transmission system, in which the main station 01 and each terminal 02 (02 ₁ to 0
_2o ) are connected in a loop through a transmission line 03.
During normal communication, the transmitted data of main station 01 is sent to transmission terminal 2.
is output from terminal 02 ₂ via terminal 02 ₁ ,
..., terminal 02o _-1 , terminal _02o , and then returns to the main station 01 via the receiving terminal 1. As a result, the data transmitted from the main station 01 is received by all the terminals 02 ₁ to 02 _o . When each terminal ₀₂₁ to _02o receives the transmission data specifying the terminal from the main station 01, it compares the address set in advance for its own terminal with the specified address from the main station 01, and if they match, it sends the data to the main station. The terminal is configured to send data held by its own terminal following the data transmitted from station 01. During the period when the designated terminal is sending data to the loop, other terminals and the main station will be in the receiving state, and only the designated terminal will use the loop to transmit its own address and own terminal data. . For this reason, main station 01 and all terminals are in either transmit mode or receive bypass mode, and when in receive bypass mode, they have the function of importing transmitted data internally and bypassing the transmitted data to the next transmission path. It is configured as follows. In this way, the transmitted data from the specified terminal goes around the loop once and returns to its own terminal, so master station 01 and all other terminals that are in reception bypass mode can receive the data and are not sent. The transmitted data includes the destination terminal address and terminal data, so each terminal compares the address in the received data with the address data set for itself, and then imports the data destined for itself. In this way, data transmission between designated terminals is possible, and the main station can not only receive terminal data but also monitor communication data between terminals. FIG. 3 is a block diagram of the loop transmission control circuit 04 provided in the main station and the terminal. In the figure, 1 is a receiving terminal, 2 is a transmitting terminal,
3 and 4 are level converters, 5 is a transmission signal line, 6
is a start bit detector, 7 is a synchronous clock generator, 8 is a sampling circuit, 9 and 10 are AND circuits, 11 is an OR circuit, 12 is an inverter circuit, 1
3 is a transmission data selection circuit, 14 is a start bit detection signal line, 15 is a synchronous clock signal line, 16 is a reception bypass signal line, 17 is a transmission signal line, 18 is a transmission/reception switching signal line, 19
indicates a microcomputer (hereinafter also referred to as a microcomputer). The operation of this loop transmission control circuit is as follows. The level converter 3 converts the received signal into a signal at a signal voltage level (for example, TTL level) within the loop transmission control circuit 04. The converted received signal starts a synchronous clock generator 7 when a start bit is detected by the start bit detector 6. The sampling circuit 8 detects the received signal line 5 at the rising edge of the synchronous clock waveform from the synchronous clock generator 7.
By sampling the voltage level of the receiving bypass signal line 1 of the same level (e.g. TTL level)
Output to 6. The transmission data selection circuit 13 transmits the signal on the bypass signal line 16 during reception, and the signal on the transmission signal line 17 during transmission, to the level converter 4 according to the contents of the transmission/reception switching signal line 18. The level converter 4 converts the voltage level used within the device (TTL level) again into a signal external to this device and transmits it to the next device. The microcomputer 19 has a function to perform serial transmission, and when receiving a serial signal, it sets the transmission/reception switching signal line 18 to "H" level, and also outputs the synchronization clock on the synchronization clock signal line 15 generated by the start bit of the received data. By sampling the level of the received signal line 5 at the rising edge of , serial data can be read. Further, when transmitting a serial signal, the transmission/reception switching signal line 18 is set to "L" level, and serial transmission data can be output from the transmission signal line 17. In this way, the received signal converted by the level converter 3 can bypass this device via the sampling circuit 8 and be retransmitted onto the transmission line 03 by the level converter 4 again. . Through such operations, the microcomputer 19 can receive data from other stations, and can also transmit proprietary data within its own station if necessary. Immediately after power is turned on, the main station 01 sets the transmission/reception switching signal S4 output from the microcomputer 19 to the "L" level on the transmitting side, as shown in FIG. In this example, 2 words of one-round transmission time measurement data LD are output, and this measurement data LD connects the loop transmission line 03 shown in FIG.
local station 01 via reception terminal 1 shown in Figure 3.
The one-round transmission time LT1 until input to the microcomputer 19 within is measured. Figure 1 is a timing chart for measuring this one-round transmission time LT1.
2 is the one-round transmission time timer LTM
3 is the timing at which the one-round transmission time measurement data LD is transmitted from the transmission terminal 2 of the main station, and 4 is the timing at which the measurement data LD is received from the reception terminal 1 of the main station. Each is shown below. To explain FIG. 1 with reference to FIG. 3, when the microcomputer 19 of the main station 01 determines that the power is turned on, the microcomputer 19 of the main station 01 immediately before outputting data LD for measuring one round transmission time from the transmission terminal 2 of the main station 01 (at the point in time) t1), the microcontroller 19's built-in one-round transmission time measurement timer
When the LTM is started and the one-round time measurement data LD output by the main station 01 is input to the transmission terminal 1 of the main station 01 at time t2, the microcomputer 19 stops the one-round transmission time measurement timer LTM and performs the measurement. Let timer LTM clock data be one round transmission time LT1. Main station 01
The microcomputer 19 calculates this timing data (one round transmission time
In order to improve the reliability of LT1), this measurement communication is performed multiple times, and the correct one-round transmission time is determined by matching the data of the measured one-round transmission time LT1 many times.
LT1 may be determined. In addition, although Fig. 1 shows the timing of measurement communication when the power is turned on, even if the transmission loop is restored after being cut off, this point is also
9 makes a determination according to a predetermined procedure, and 1 at the same timing.
If the measurement of the transmission time is carried out, it will be accompanied by a change in the system. 1 automatically even if the loop length changes.
The transmission time can be reset. By measuring the transmission time for one round of the loop as described above, the microcomputer 19 in the main station 01 calculates the transmission time for one round of the loop.
Round up LT1 to a certain time interval,
Performs compression processing in several stages. For example, as shown in the table below, 0~32μs is 32μs, 33~64μs is 64μs,
...... 225 to 256 μs is expressed as 256 μs, and so on, and is expressed in 8 steps in 32 μs increments as 3-bit (b2 to b0) time information (referred to as one-round transmission time data LT2).

[Table] Therefore, in this case, if the one-round transmission time LT1 of 256 μs or more is obtained by measuring the one-round transmission time of the loop, a system error will occur. Next, the main station 01 performs special communication with each terminal 02, or transmits the one-round transmission time data LT2 to all terminals by normal communication with the terminals as in the transmission format shown in FIG. That is, FIG. 2A shows the transmission format during normal communication between the main station 01 and each terminal 02, and FIG. 2B is a detailed enlarged view of the main station command data DT1 in FIG. 2A. In the figure A, the main station command data DT1 is the main station 01
This includes the command issued to terminal 02 and the data described below. In addition, DT2 is station transmission data, and each designated terminal sequentially receives data (main station transmission data) from the main station or transmits it from each terminal to the main station sequentially based on the main station command data DT1. This is the data (terminal station transmission data) part. Next, in the detailed enlarged view of the master station command data DT1 in Figure 2B, DT11 and DT12 are each 8
Of the first and second characters of the bit, the second character DT12 is the inverted data of the first character DT11, and is used for transmission error checking. In addition, the first character DT11 is 2 and 3, respectively.
and three 3-bit data, namely transmission mode data MD, terminal block address data BA, and the above-mentioned one-cycle transmission time data LT2. Here, the transmission mode data MD is data indicating the content of this command, that is, a command to transmit data from the main station 01 to the terminal 02 side, or a command that the main station 01 receives data from the terminal 02 side, etc. be. Further, the terminal block address data is the address data of the block to which the terminal 02 address that is the object of this communication belongs. These block addresses are assigned in advance to each predetermined plurality of terminal address groups, and the communication order of each terminal address within the group is predetermined. By transmitting this terminal block address data BA to the terminal side, each terminal belonging to the block address enters a communication preparation state, and as shown in FIG.
This means that communication with the main station is performed sequentially using the station transmission data DT2. Now, in normal communication, when the main station command data DT1 is first transmitted to the main station or the terminal side, all the terminals 20 on the loop receive these two character data from the main station 01, and the first character DT11
According to the signal mode data MD and terminal block address data BA contained in Remember. Note that the weighting of the 1-bit data LT2 indicating the transmission time for one round of the loop is determined by each microcomputer 1 of the main station 01 and terminal 02.
It is considered to be the same by the program No. 9. When the main station 01 and the terminal 02 are in the transmission mode and finish transmitting the transmission data from the transmission terminal 2, the time required to switch the transmission/reception switching signal S4 from the transmission side "L" level to the transmission bypass side "H" level in FIG. By waiting for the time determined by the transmission time LT2,
During this waiting period, the output signal of the sampling circuit 8 for bypassing the received data (receiving bypass signal S3)
Since the data is not transmitted to the transmission terminal 2 side, it is possible to prevent the transmission output data of the local station from going around the loop 03 twice. Also, regarding the timing of transitioning from reception bypass mode to transmission mode, after other stations have finished transmitting, wait for a certain period of time to stop data bypass, and then transmit after all other stations have entered reception bypass mode. Since it is possible to switch between modes, the transmission timing can be created so that the transmitted data will not be interrupted on the way.

【Effect of the invention】

As is clear from the above description, according to the present invention, in a loop data transmission system in which a main station that controls transmission and a plurality of terminal stations are connected via a loop-shaped transmission path, power-on of the main station, etc. The main station automatically transmits predetermined time measurement data onto the loop, calculates the transmission time for one round of the loop from the time of transmission of this measurement data to the time of reception, and then A predetermined standby time based on this transmission time is transmitted from the main station to all terminals, and after each station sends data, it maintains the transmission mode until this standby time has elapsed to avoid data bypass. As a result, each station can transmit data transmitted from its own station to two without putting a burden on the transmission control software.
This will prevent you from going through the loop more than once. Furthermore, even if the transmission time for one round of the loop differs due to differences or changes in the system configuration, the standby time can be automatically reset without changing the program.

[Brief explanation of drawings]

FIG. 1 is a time chart explaining the operation of the main part of the main station as an embodiment of the present invention, FIG. 2 is a diagram showing the transmission format of communication between the main station and the terminal, and FIG. The block diagram shown in FIG. 4, which shows the configuration of the loop transmission control circuit in each station, is
Similarly, FIG. 5 is a block diagram showing the structure of a loop data transmission system. 01: Main station, 02 (02 ₁ to 02 _o ): Terminal station (terminal), 03: Transmission path, 04: Loop transmission control circuit, LD: Data for measuring one round transmission time, LTM: 1
Cycle transmission time measurement timer, LT1: 1 cycle transmission time,
LT2: 1 round transmission time data, DT1: Main station command data, DT11: 1st character.

Claims (1)

[Claims] 1. A main station that controls transmission, a plurality of terminal stations, and a transmission line that sequentially connects each of the stations in a loop and transmits data in a predetermined direction, and each station is always connected to the transmission line. It is possible to receive data via the adjacent station on the receiving side, and when in reception bypass mode, further bypass-transmits this received data as it is to the adjacent station on the transmission side of the transmission path, and when in transmission mode, the above-mentioned In a loop transmission system in which data is transmitted to an adjacent station on the transmitting side and data is transmitted by cutting off the bypass described above, at least the main station communicates with each terminal station. Under predetermined conditions, all terminals are kept in reception bypass mode, and predetermined time measurement data is transmitted to the adjacent station on the transmitting side, and after this transmission, the transmission line is disconnected from the adjacent station on the receiving side. Means for measuring the transmission time for one round until receiving the time measurement data that has circulated, and means for transmitting a predetermined waiting time including at least the time to all terminal stations based on this measurement. and a means provided at each station for maintaining the transmission mode until the standby time has elapsed after the station has finished transmitting, and then switching to the reception bypass mode. Transmission error prevention device.