JPS62196948A - Transmission system containing loop type transmission line - Google Patents

Abstract

PURPOSE:To attain the fast response to the change of a transmission system by setting a transmission line which switches a steady transmission driver and a back-up transmission driver under a no-signal state for fixed time in case a new slave station is connected or a certain slave station stops its transmitting action. CONSTITUTION:When the reset signal is set at 'H', a transmission driver 7 is inactivated after a transistor TR is turned on and a capacitor C1 is quickly discharged through a diode D1. While a transmission driver 8 charges a capacitor C2 through a resistance R3 and the control signal CNT1 of the driver 8 is equal to the threshold voltage Vth after a time T2 decided by a time constant. Thus the signal CNT1 is regarded as 'H' and the driver 8 becomes active. In other words, a cut-off mode (no-signal state) is kept until the time T2 passed from a repeating mode and then an on-line mode is set. here a master station 2 confirms that the no-signal state lasts the detecting time T or longer and performs the initialization processing to perform transmission based on the state of a new system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a transmission method for a transmission system having a loop-shaped transmission path.

[Background Art] FIG. 3 shows a loop-shaped transmission line 1 with a master station 2 and a plurality of slave stations 3I.
... is connected, and the accessed slave station transmits data to the master station 2 through the next slave stations one after another based on commands sent from the master station 2 and sent through the previous slave stations one after another. The figure shows a transmission system in which data is sent and received between the master station 2 and each slave station 31 by transmitting or taking in data sent successively through several stages of slave stations. By the way, in this type of system, in order to prevent the transmission system from functioning down even if a certain slave station suffers a momentary power outage or power outage, each slave station 3. The transmitter/receiver circuit 4 of .
), the control signal CNTO of the steady-state dry parameter becomes inactive and stops operating as shown in FIG. 5(b), and at the same time the backup driver 6 becomes active. Then, the received signal of the slave station is directly transmitted to the next slave station, that is, the online mode is quickly switched to the relay mode, and the loop transmission system can transmit the signal without any loss of function.

By the way, the master station 2 is connected to each slave station 3. For example, in a system where the distribution data of the number of input/output points is captured in the initialization process and converted into a table, and the table is transmitted to each slave station, when the status of the slave station changes, the actual number of input/output points changes. The operation will be different from the distribution, resulting in abnormal operation of the control system.

Conversely, a similar situation occurs when a new slave station is connected to the transmission line 1.

[Object of the Invention] The present invention was made in view of the above-mentioned problems, and its purpose is to enable the master station to detect changes in the transmission system when they occur, and to determine the status of the new system. The object of the present invention is to provide a transmission method for a transmission system having a loop-shaped transmission path that can be reconfigured.

[Disclosure of the Invention] The present invention is characterized in that a master station and a plurality of slave stations are connected to a loop-shaped transmission line, data is exchanged between the master station and each slave station through the transmission line, and the transmission is in a steady state. In a transmission system that has a loop-shaped transmission path that is affected by state parameters, when a new slave station is connected or a slave station stops transmitting, the regular transmission driver and the backup transmission driver The transmission line is set to a no-signal state for a certain period of time by means of a switching means for switching.

The present invention will be explained below with reference to Examples.

FIG. 1 shows a transmitting/receiving circuit section 4 of an embodiment that realizes the method of the present invention.
This indicates that the transmitter/receiver circuit 4 is unable to guarantee operation due to a power outage in the slave station, and the Re5et signal is low.
Then, the control signal CNTl becomes "L" because the charge of the capacitor C2 passes through the diode D2 and is rapidly discharged. Also, the control signal CNT2 becomes "L" because the transistor T" turns off, so the resistor is turned off by the backup power supply vb. The capacitor C1 is charged through R1°R2, and reaches the threshold voltage vth at which the transmission driver 7 becomes active with a time constant (R1+R2) CI, and is regarded as "H".

The above is illustrated as shown in FIGS. 2(a) to 2(c), where the Re5et signal and the control signal CNTl.

During T1 from the time when the Re5et signal becomes "°°L", CNT2 is controlled by the transmission driver 7.8 as well as the time TI (time constant (R)).
1+R1) (determined by CI), there is no signal. In other words, the cutting mode is set. After this time T1 has elapsed, the transmission driver 7 becomes active and enters a relay mode in which a relay operation is performed. At this time, the master station 2 has been in a no-signal state for a period of time 'r
(However, T < T +, T < T 2) By confirming that the above is true, it is possible to detect a change in the state of the transmission system due to a power outage, etc., and after the slave station enters relay mode,
The case where the next new slave station changes from the relay mode to the online mode, in which the above-mentioned initialization process is performed again and transmission can be performed based on the new system state, will be described. In this case, the Res■ signal is °'
When the voltage reaches H°, the transistor 'rr of the transmission driver 7 shown in FIG. 1 turns on, causing the capacitor C0 to rapidly discharge through the diode D1, and becomes inactive. In addition, the transmission driver 8 passes the transmission R1 through the transmission driver 1.
- the capacitor C is energized, and after a time T2 determined by the time constant R3XC2, the control signal CN of the transmission driver 8 is
Tl becomes the threshold voltage Vth and is considered to be 'H'', and the transmission driver 8 becomes active.Illustrating the operation of 0 or more, as shown in FIG. (no signal state) and then enters online mode.At this time, the master station 2 has been in a no signal state for a detection time T (however, T<T).

By confirming that T<T2) or more, the new slave station enters online mode (master station 2 does not know how to distinguish it from when the power is cut off, but it detects that there is a change in the system) and detects that the system has changed. However, after the disconnection mode ends, initialization processing is performed in the same manner as described above, and transmission can be performed based on the new system state.

In this way, it is possible to perform operations based on a new system in response to changes in the state of the transmission system, and by detecting with hardware, it is possible to respond to changes in the transmission system at high speed.

"Effects of the Invention" In the present invention, a master station and a plurality of slave stations are connected to a loop-shaped transmission line, data is exchanged between the master station and each slave station through the transmission line, and the transmission is in a steady state. In a transmission system with a loop-shaped transmission path that is affected by state parameters, when a new slave station is connected or when a slave station stops transmitting, the regular transmission driver and the backup transmission driver Since the transmission path is set to a no-signal state for a certain period of time by the switching means that switches the transmission line, if the no-signal state is detected, operation based on a new system can be performed in response to a change in the state of the transmission system, and the hardware By detecting this, it is possible to quickly respond to changes in the transmission system.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a transmitting/receiving circuit according to an embodiment of the present invention, Fig. 2 is a time chart for explaining the operation of the same, Fig. 3 is a schematic circuit diagram of a transmission system, and Fig. 4 is a circuit diagram of a conventional example. , FIG. 5 is a time chart for explaining the operation of the same as above,
1 is a transmission path, 2 is a master station, 31... are slave stations, and 4 is a transmitting/receiving circuit. 13'A Figure 5

Claims (1)

[Claims] (1) A master station and multiple slave stations are connected to a loop-shaped transmission line, and data is exchanged between the master station and each slave station through the transmission line, and the transmission is based on the parameters of the steady state. In a transmission system having an affected loop-shaped transmission path, when a new slave station is connected or a slave station stops transmitting, a switching means switches between a normal transmission driver and a backup transmission driver. A transmission method for a transmission system having a loop-shaped transmission line, which is characterized by setting the transmission line in a no-signal state for a certain period of time.