JPH0475697B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of the Invention The present invention relates to a multiplex transmission device in which a primary station and a plurality of secondary stations are loop-connected in a digital chain manner using a two-core dedicated line.

(b) Prior art and its problems Generally, in a multiplex transmission device that connects a primary station and a plurality of secondary stations using a two-core dedicated line, each secondary station requires a unique address. However, there are problems with operability when setting addresses, such as erroneous settings occurring on site. On the other hand, in order to improve operability in the field, there is a conventional shift register method that does not specify an address, but this transmission method requires the transmission of a clock signal in addition to the data signal, which cannot be handled with a 2-core dedicated line. First, it had the disadvantage of not being able to reduce the cost of transmission cables.

(c) Purpose of the Invention In view of the above, the purpose of the present invention is to improve operability in the field without reducing the cost of transmission cables.
It is an object of the present invention to provide a multiplex transmission device that can also determine abnormalities in secondary stations.

(d) Structure and Effects of the Invention In order to achieve the above object, the multiplex transmission device of the present invention connects a primary station and a plurality of secondary stations in a digital chain manner using a two-core transmission line, and 2
means for receiving a polling signal from a priority station to the next station; means for transmitting a data signal of the own station having a higher frequency than the polling signal in response to reception of the polling signal; and the received polling signal The station is equipped with a polling signal reproducing means for reproducing the data signal and transmitting a polling signal following the data signal, and a filter means for passing only the data signal from the priority station.

According to this invention, polling signals and data signals are transmitted using only two-core transmission lines, so there is no increase in transmission cable costs, and since address setting is not performed at the secondary station, it is possible to
Improves operability at the next station. Furthermore, by checking the data signals and polling signals that are sequentially transmitted on the primary station side, it is possible to monitor abnormalities such as power outage of each secondary station.

(e) Description of Examples The present invention will be explained in more detail below with reference to Examples.

FIG. 1 is a schematic block diagram of a multiplex transmission apparatus showing one embodiment of the present invention. In the figure, a primary station 1 and a plurality of secondary stations 2a, 2b, 2c, 2d
are connected in a digital chain loop using a two-core transmission line 3. That is, the output terminal (OUT) of the primary station 1 is connected to the input terminal of the secondary station 2a, the output terminal of the secondary station 2a is connected to the input terminal of the secondary station 2b, and the output terminal (OUT) of the primary station 1 is connected to the input terminal of the secondary station 2b. Connected to 2c and 2d,
The output terminal of secondary station 2d is the input terminal (IN) of primary station 1.
It is connected to the. Note that 4a, 4b, 4c, 4d
are switches provided in each of the secondary stations 2a, 2b, 2c, and 2d.

An outline of the operation of this multiplex transmission device will be explained with reference to a signal time chart shown in FIG. First, 1
First, the polling pulse (signal) shown in a of FIG. 4 is output from the output terminal OUT of the next station 1. When the secondary station 2a receives this polling pulse, it outputs a data signal according to the on/off state of the connected switch 4a. This data signal is a pulse signal with a frequency much higher than the frequency of the polling pulse, and is sent out for a time width twice as long when the switch 4a is on as compared to when it is off. The secondary station 2a also reproduces the polling pulse and sends the polling pulse to the next-ranked secondary station 2b following its own data signal. Therefore, the signal sent out from the secondary station 2a is as shown in b of FIG. Next, at the secondary station 2b,
The data signal in the signal b sent from the secondary station 2a is passed through and output as is, and in response to the polling pulse in the signal b, the data signal is output according to the on/off state of the switch 4b of the own station. Then, the polling pulse is regenerated and sent to the next station 2c. Therefore, from the secondary station 2b to the secondary station 2c, as shown in FIG.
The data signal of the secondary station 2b, the data signal of the secondary station 2b, and the polling pulse are transmitted in this order. Similarly, the secondary stations 2c and 2d pass the data signal from the higher priority station as is, receive the polling pulse from the higher priority station, send out their own data signal, and finally send the polling pulse. Play and send. Therefore, the signals sent from the secondary stations 2c and 2d are as shown in FIG. 4d and e, and the signal e output from the secondary station 2d is the input terminal of the primary station
Input to IN. As described above, the primary station 1
According to the polling, data signals from each secondary station are transmitted to the primary station 1. Therefore, each secondary station does not require a unique address.

Figure 2 shows each secondary station 2, 2a, 2b, 2c, 2
d is a block diagram showing a specific circuit configuration of the circuit.
In the figure, reference numeral 21 is a high-pass filter that allows only the data signal input to the input terminal 21IN to pass through and sends it to the output terminal 20OUT. The polling pulse is attenuated by this high pass filter 21. Furthermore, this high-pass filter 21 is a passive filter consisting of a coil L and a capacitor C, and therefore, the data signal passes through it as is regardless of whether the secondary station 2 is powered on or off.

22 is a low-pass filter, and the input terminal IN
Pass only the polling pulse input to the
The data signal is adapted to be attenuated. The output of this low-pass filter 22 is input to a flip-flop of a circuit 23 including a flip-flop and an AND circuit. 24 is an oscillator that generates a high frequency signal for data signals;
The output is applied to the AND circuit input terminal of the circuit 23 and also to one input terminal of the logic circuit 25. The AND circuit of the circuit 23 receives the flip-flop output and the pulse signal from the oscillator 24, and inputs the output to the counter 26. The intermediate stage outputs C1 and C2 of the counter 26 are input to the logic circuit 25, and the first stage output C3 is input to the polling pulse regeneration circuit 27.

The logic circuit 25 includes switches 4, 4a, 4b, 4
After receiving the signal G from c and 4d, the signal G turns on.
(high), the pulse signal from the oscillator 24 is output for a period corresponding to the output C2 of the counter 26, and when the signal G is off (low), the counter 26
The oscillator 24 is configured to output a pulse signal during a period corresponding to the output C1 of the oscillator 24.

The polling pulse regeneration circuit 27 has a counter 26
When it receives the output C3, it generates a polling pulse and sends it out through the low-pass filter 28. Upon completion of the transmission, the flip-flop and counter 26 of the circuit 23 are reset and initialized in preparation for reception of the next polling signal. Reference numeral 29 denotes a data signal transmitting circuit, which transmits a data signal of the number of pulses corresponding to the on/off state of the switch 4 from the logic circuit 25 via the high-pass filter 30.

Next, the operation of the secondary station 4 will be explained. When a data signal is input from the priority station to the input terminal 2IN, this data signal is passed through the high pass filter 21.
The signal is sent to the output terminal 2OUT without being attenuated.

When the polling pulse (see FIG. 5B) is input, it is applied to the flip-flop of the circuit 23 through the low-pass filter 22, and the flip-flop is set (see FIG. 5C). Since the high frequency pulse signal shown in FIG. 5A is input from the oscillator 24 to the circuit 23, while the flip-flop of the circuit 23 is being set, this pulse signal is input from the circuit 23 to the counter 26 ( (See Figure 5D).

Assuming that the switch 4 is now on (see FIG. 5G), the pulse signal from the oscillator 24 is output from the logic circuit 25 during the period corresponding to the output terminal C2 of the counter 26 (see FIG. 5F). (See FIG. 5H), and this pulse signal is sent out as a data signal from the data signal transmitting circuit 29 via the high-pass filter 30 (see FIG. 5I). When the switch 4 is off, the pulse signal from the oscillator 24 is output from the logic circuit 25 during a period corresponding to the output C1 of the counter 26 (half the period when it is on).

When the count of the counter 26 advances and the output C3 becomes high (see Fig. 5E), the polling pulse regeneration circuit 27 generates a polling pulse in response to this output, and transmits the polling pulse to the next ranking station through the low-pass filter 28. Send (Figure 5 I)
reference).

FIG. 3 is a block diagram showing the configuration of the primary station 1. As shown in FIG.

The primary station 1 includes a microprocessor 31, a polling pulse generator 36 including an oscillator 32, a counter 33, a polling transmitter 34, and a low-pass filter 35, a polling pulse receiver 38 including a low-pass filter 37, and a high-pass filter 39. , a data signal receiving section 4 including a waveform shaping section 40
1, an input/output status display section 42 and an abnormality display section 43
It consists of

The transmission and reception of polling pulses and the reception of data signals in the primary station 1 are controlled by a microprocessor 31.

The operation of the primary station 1 will be explained with reference to the flowchart shown in FIG.

After the operation starts, step ST (hereinafter abbreviated as ST)
1, the polling pulse generator 36 sends out one polling signal. Then, a polling pulse monitoring timer built into the microprocessor 31 is started (ST2). This polling pulse monitoring timer is a timer for monitoring whether the sent polling pulse returns within a predetermined time.

Next, is there input 1? That is, it is determined whether or not a data signal has been sent out via the data signal receiving section 41 (ST3). Data signal is secondary station 2
As long as it is not transmitted from d, the judgment is NO.
Next, ST checks whether the monitoring timer has timed up or not.
Judgment is made with 9 until the monitoring timer times up.
Repeat the determination in ST3 and ST9.

When the data signal is transmitted, the determination in ST3 becomes YES, so a count of 1 is performed in ST4 to indicate that the data signal has been received once. Then, by counting the number of pulses of the received data signal, it is determined whether the total pulse width of the data signal is long (ST5). If the pulse width is long as a result of the determination, it means that the switch of that secondary station is turned on, so input ON display processing is performed (ST6). The first data signal transmitted is 2
Since the signal is from the secondary station 2a, the light emitting diode for displaying the secondary station 2a in the input/output status display section 42 is turned on. If the pulse width is short in ST5,
Input OFF display processing is performed (ST7). That is, the light emitting diode for the secondary station 2a of the input/output status display section 42 is not turned on.

Following the display processing in ST6 or ST7, is there input 2? , that is, the polling pulse receiving section 38
After that, it is determined whether a polling pulse has been transmitted (ST8).

The polling pulse is transmitted at the end of the data signal from each secondary station, so at the stage when the data signal from the secondary station 2a is received,
This determination is NO, and the process returns to ST3 via ST9. Then, in the same way as above, ST3~ST
8 is repeated, and in response to the sequential reception of data signals from the secondary stations 2b, 2c, and 2d, each corresponding input is displayed as ON or OFF. When the reception of data signals from all secondary stations 2a, 2b, 2c, and 2d is completed and the polling pulse is finally received, the determination in ST8 becomes YES. Therefore, the operation returns to ST1 and the polling pulse is sent out again.

The above is the operation when each secondary station is normal.
If any of the secondary stations has an abnormality such as power outage,
Data signals and polling pulses from the secondary station onward are not transmitted. For example, if the secondary station 2c is powered off, the data signal and polling pulse will not be received following the reception of the data signal from the secondary station 2b, so ST3 to ST8 → ST9 → ST3 will not be received until the monitoring timer times up. The operation is repeated. When the monitoring timer times up, in ST10, the secondary station of the value obtained by adding 1 to the number of data signal reception
The abnormality display unit 43 displays that the third station that received +1, that is, the secondary station 2c, is abnormal.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a multiplex transmission device showing one embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a secondary station of the same multiplex transmission device, and FIG. 3 is a block diagram of a primary station of the same multiplex transmission device. Block diagram showing the configuration of the station, No. 4
The figure is a signal time chart for explaining the general operation of the multiplex transmission equipment, FIG. 5 is a signal waveform time chart for each part to explain the operation of the secondary station, and FIG.
The figure is a flow diagram for explaining the operation of the primary station. 1...Primary station, 2a, 2b, 2c, 2d...2
Next station, 3...Transmission line, 21, 30...High pass filter, 22, 28...Low pass filter, 27
. . . Polling pulse regeneration circuit, 29 . . . Data signal transmission circuit.

Claims (1)

[Claims] 1. A primary station and a plurality of secondary stations are connected in a digital chain loop using a two-core transmission line, and each secondary station is provided with a means for receiving a polling signal from a priority station, and a means for receiving the polling signal. means for transmitting its own data signal having a higher frequency than the polling signal in response to the polling signal; and polling signal reproducing means for reproducing the received polling signal and transmitting the polling signal following the data signal. A multiplex transmission device comprising filter means for passing only data signals from a priority station.