JPS5836047A - Data transmission line control method - Google Patents

Abstract

PURPOSE:To obtain high efficiency of utilization of a circuit in data transmission between one master station and plural subordinate stations, by performing priority control over the advanced transmission right acquisition among the subordinate stations, and thus realizing delay system traffic. CONSTITUTION:Between a master station data terminal and plural subordinate station terminals, signal lines BU and BD for priority control over the advanced transmission right acquisition among the plural subordinate stations and signal lines DU and DD for data transmission are provided. The transmission control circuit 8 of some subordinate station outputs a transmission request signal RS and a transmission interruption pulse TRQ to an FF7 when generating data on the station. Further, the circuit 8 once inputting a transmission permit signal CS outputted from the FF7 stops the pulse TRS and outputs transmitted data SD to a gate 9. Only when the signal CS is on, the signal SD appears on the line DU-OUT and when off, the line DU-IN is connected to the line DU-OUT.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a line control system for bidirectional data transmission between one master station data terminal and a plurality of slave station data terminals.

The data line control procedure between one master station data terminal and multiple slave station data terminals is based on the basic data transmission control procedure (polling selection method) specified in JIS C6862, which is based on bidirectional alternate transmission. )or,
High-level data link (HD) for highly efficient transmission
Lc) Hand 111ffl (JIS C6868~686
5) is conventionally used. However, in the former case, the master station transfers data to all slave stations in sequence according to the data link setting procedure, so if there are many slave stations and the frequency of data generation per slave station is low. The major disadvantage of this method is that the average waiting time from data generation to data transfer at the slave station increases, and the line usage efficiency decreases significantly. Although it is better than the former, if there are many slave stations with low data volume and data generation frequency, the efficiency of line usage will decrease, and the advantage of continuous transmission of variable-length messages, which is a feature of this procedure, will not be utilized. Become.

The present invention was made in order to eliminate the above-mentioned drawbacks that occur when the amount of data per slave station and the frequency of data generation are small and the number of slave stations is large. explain.

FIG. 1 is a diagram showing an example of the configuration of a data transmission line in which the present invention is implemented. Reference numeral 1 in the figure denotes a master station data terminal (hereinafter referred to as a master station) which controls data transmission between a plurality of slave station data terminals (hereinafter referred to as slave stations). Reference numerals 2 and 3 are slave stations, which perform data transmission with the master station and mutual control over acquisition of transmission rights to the master station between the slave stations.

Between the master station and each slave station, there are BU, BD, DU,
They are connected in cascade through the DD signal transmission line. However, in FIG. 1, the slave stations after the third abutment are not shown.

Also, in order to describe the signal transmission direction and the positional relationship of slave stations based on this diagram, in the following explanation, the master station side (left side of the diagram) is referred to as the upstream direction, and the slave station side (the right side of the diagram) is referred to as the downstream direction. I'll call you. The arrows on the signal lines in Figure 1 indicate the direction of signal transmission, and the BU indicates to the master station and upstream slave stations that the downstream slave station has acquired the right to transmit data to the master station. This is a notification signal that is currently being transmitted, and BD is also a notification signal that indicates that a slave station upstream from this signal has obtained the right to transmit. (BU and BD have other uses in the master station) Furthermore, DU and DD are data signals sent out from the slave station and the master station, respectively, and transmitted in the upstream and downstream directions, respectively. In other words, in the conventional cascade connection method, DU
Although only a pair of wires for BU and DD are used in this invention,
This means that a pair of control lines for BD are added.

FIG. 2 is a detailed configuration example diagram of one of the slave stations in FIG. 1. BU-IN and BU-OUT in the figure.

BD-IN and BD-OUT are the BU for pre-emption priority control of transmission rights between slave stations, the BD double signal line, the output line, and the D
U-IN, DU-OUT, DD-IN, and DD-OUT are output lines to slave stations of DU and DD signal lines for data transmission, respectively. 4.5 is an OR logic gate (OR gate) which outputs the logical sum of each input of BU-IN and BD-IN and the transmission permission signal (C8) of its own station. 6 is a NOR gate that detects that both uplink and downlink are in a non-transmission state (set to L level) at the same time, its output TRD'Y is a line idle signal, and both BU and BD signals are set to L level. It becomes H level only when this happens. 7 is flip-flop (FF)
Then, upon receiving the TRDY signal that has become H level, it memorizes and holds this data when the local station data is generated.

CS is the output of FF'7 and is a transmission permission signal. 8 is a transmission control circuit which outputs a transmission request signal R8 and a transmission interrupt pulse TRQ to FF7 when own station data is generated. TRQ
is a transmission interrupt pulse that is output at regular intervals from the generation of the transmission request signal R8 to the generation of the transmission permission signal CS,
R8 is used to cancel the slope of F'F7, and TRQ is used as a trigger pulse. Furthermore, when the transmission control circuit 8 receives the transmission permission signal C8 which is the output of the FF7,
The RQ pulse is stopped and the transmission data signal SD is output to the gate 9. 9 is a switching gate, SD and DU-IN
Outputs one of the two inputs to DU-OUT, which is controlled by the transmission permission signal CS, and C8
SD ratio output DU-OU only when ON (H level)
When cs is O4-7 (LL/Bell), DU-IN is connected to DU-OUT.

10 to 12 are reception systems, IO and 11 are buffers for DD double signal circuit matching and shaping, 12 is a reception control circuit, and RD is an input to the circuit 12.

The circuit 12 is a circuit that performs synchronization and processing of received data.

Note that the transmission control circuit 8 and the reception control circuit 12 may include a data modulator/demodulator. Further, although FIG. 2 shows an example of a hardware configuration, the functions expressed by gates and FFs may be realized by software.

Now, the procedure of data transmission line control between one master station and a plurality of slave stations will be explained with reference to FIG.

FIG. 8 is a time chart of an operation example of one slave station (referred to as M), and the symbols on the left side of the diagram correspond to the signals of each part shown in FIG. 2, respectively. H and L on the right side of the figure indicate the state of the signal, with H indicating on (signal present) and L indicating off (no signal) or high or low voltage level. Furthermore, portions indicated by m and n indicate respective transmission data of a certain slave station M (not shown) and another slave station N (not shown) on the upstream and downstream sides of M. If no signal is being sent, BU-IN, DU-
INBU-OUT and DU-OUT are all at L level.

Assume that a third slave station (referred to as K) located upstream from the current slave station M is transmitting data to the master station. At this time, the station sets BU-OUT to the upstream slave station (2) and BD-OUT to the downstream slave station from K to H level, so slave station M sets the intermediate station to H level. The H-level BD double signal that comes in via transfer is input from BD-IN in FIG. 2, and the transmission control circuit 8 of the slave station M sets the line idle signal TRDY to the L level, so FF7 is not sent. Even if station M generates a transmission request signal R8 from the transmission control circuit 8, transmission is not permitted.Also, for slave stations upstream from the station, B
Since the BU multiplied signal of H level is sent from U-IN and the line idle signal TRDY is kept at L level, transmission from these slave stations is similarly not permitted.

Next, at the time point ■ in Figure 3, transmission to the slave station ends, and BD and B
If a transmission request has occurred at a downstream slave station N from slave station M when both U and U signals go to L level, then slave station N
The line free signal TRDY is H as in all other slave stations.
Immediately after this change, the first transmission interrupt pulse TRQ generated from the transmission control circuit 8 of the N station causes the time point shown in FIG. 8 (BU-IN changes to H level).
FF7 is set, the slave station N outputs H level BU and BD double signals to the upstream and downstream slave stations, and the transmission of data n from the master station is started. This data n appears on the DU-IN of the slave station M because the slave station M is used as a relay, and the DU
-OUT and is transmitted to the master station (2).At this time, since BU-(N of slave station M is at H level, a data transmission request signal R8 is generated to slave station M at the time point (■) in Fig. 8). Even if it is sent, FF7 is not sent, and transmission is not permitted, as in the case above.

When the data transmission of slave station N ends at the time shown in Figure 3 ■, BU
Both the double signal BD and the double signal become L level, and the transmission free signal TRDY of slave station M changes to H level, and immediately after that, FF7 is activated by the transmission interrupt pulse TRQ of M station, which has previously generated the data transmission request signal R8. is set, and its output is the transmission permission signal C8.
becomes H level. Due to this C8 power, the transmission control circuit 8 of the M station stops sending out the transmission interrupt pulse TRQ, and transfers the data m of its own station from SD to S by the H level C8 signal.
D side (DU-O via two switching gates 9)
Output to UT and send to master station). During this time, BU-OUT, B for all upstream and downstream slave stations of slave station M
By setting the D-OUT to the H level of C8, it is notified that the transmission is in progress, and the TRDY of other slave stations is set to the L level (=
transmission permissions of other slave stations are prohibited.

When the data transmission of the slave station M ends at point 0 in FIG. 3, the transmission control circuit 8 of the M station sets the transmission request signal R8 to L level, and
Since FF7 is reset for this reason, the transmission permission signal C8 of the M station becomes L level, and the transmission system of the M station returns to the initial state.

ah is an explanation of the control operation in the case where the data transmission request generation order is, for example, slave station K upstream from station M, slave station N downstream, and slave station M, but it is clear from FIG. As such, in the present invention, preemptive priority control of the data transmission rights of the slave stations to the master station is performed between the slave stations using the signal line BU.

This is done using BD. Note that there is an extremely rare case where data is generated at the same time in multiple slave stations, and the times of the transmission interrupt pulses TRQ coincidentally, causing multiple slave stations to enter the ('''-transmission enabled state (C8-H level) at the same time). However, in this case (2), the slave station located furthest upstream among these slave stations blocks the transmission data from the downstream slave stations through the switching gate 9, so that the master station Only the data from the slave station is received normally.In this case, even though the downstream slave station is transmitting its own data (C8 is at H level), the BD-
Since the transmission control unit 8 (2) detects that IN is at H level, it transmits its own transmission data.

It is possible to recognize that the transmission request signal R8 has become invalid, set the transmission request signal R8 at the H level to the L level, initialize it, and take retransmission means.

Next (transmission control of downlink data from one parent station to one slave station): This will be explained. As shown in the circuit diagrams of FIGS. 1 and 2, DD-IN and DD-OUT allow all slave stations to monitor the reception of data from the master station using the reception control circuit 12.
Therefore, the master station can adopt a random selection method in which the master station specifies the slave station to which it wants to give data at any time and sends the data. The BU double signal input to the master station is used for line monitoring in the master station, and the BD double signal output from the master station is used as a transmission prohibition control signal for all slave stations.

As explained in detail above, according to the present invention, in data transmission between one master station and a large number of slave stations with a small amount of data or a low frequency of data occurrence, priority control is performed to preempt transmission rights among the slave stations. , high line usage efficiency can be obtained by implementing waiting-type traffic. In addition, in the control method of the present invention, compared to the conventional cascade connection method as described above, it is necessary to add two signal lines for preemption priority control, but the master station controls the so-called transmission right setting (polling) of the slave stations. ) function, the line usage efficiency is extremely high, and there is no need for equipment to implement the polling function, which has the advantage of low equipment costs. suitable for the system.

Furthermore, (1) As is clear from the configurations shown in FIGS. Since it is possible to switch to the polling/selection mode while maintaining the line configuration (FIG. 1), there is also an advantage in terms of versatility.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the configuration of a data transmission line in which the present invention is implemented;
FIG. 2 is a diagram showing a configuration example of one of the slave stations in FIG. 1, and FIG. 8 is a diagram showing an example of the operation of the slave station. ■・・・Master station, 2, 3-・・・Slave station, 4, 5
...-OR gate, 6...NOR gate, 7
...Flip-flop circuit, 8...Transmission control circuit, 9...Switching gate, 10.11...Buffer amplifier, 12...Reception control circuit. Patent Applicant: Kokusai Electric Co., Ltd. η3 Figure □ Inter-procedural amendment (spontaneous) August 26, 1980 Commissioner of the Patent Office Kazuo Wakasugi 1 Indication of case Patent Application No. 133282/1982 2 Name of invention data Transmission line control method 3 Relationship to the case of the person making the amendment Applicant (112) Kokusai Denki Co., Ltd. 4, Agent 1-23-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo "Claims" column of the specification [ Scope of Claims] In the same data transmission circuit 'ifMVC' between one master station data terminal and each of a plurality of slave station data terminals,
Connect the master station and all the slave stations in series using two pairs of wires, and when the first slave station starts transmitting to the master station, connect the first pair of the two pairs of connecting wires in 1. control to prohibit transmission of all other slave stations via the 271st connection line, and data transmission from the slave station to the master station via the 271st connection line, and data from the master station by specifying a slave station at any time. A method of controlling a data transmission line, characterized by performing transmission.

Claims (1)

[Claims] In a bidirectional data transmission line between one master station data terminal and each of a plurality of slave station data terminals, the master station and the gold child station are sequentially connected in cascade by two pairs of wires, and the first slave station In response to the start of transmission from 1. A data transmission line control method characterized by transmitting data from a slave station to a master station via a slave station, and transmitting data from the master station by specifying a slave station at any time.