JPH08163153A - Bus type duplex transmission device - Google Patents

Abstract

PURPOSE: To reduce the cost and to improve the performance of a bus type duplex transmission device by discriminating a normal transmission line system from the abnormal one and transmitting simultaneously plural data to a node through the normal transmission line system. CONSTITUTION: The A and B system transmission lines 1a and 1b are connected to the nodes where the transmitters 4a and 4b and the receivers 5a and 5b are connected to both lines 1a and 1b. An abnormality detection circuit 6 is connected to the input stages of receivers 5a and 5b together with a system selector 8 connected to the output stages of both receivers respectively. A system switch control circuit 7 is provided on the output stage of the circuit 6 and the transmission data are sent at a time to both systems A and B in a normal mode. If the line 1a or 1b has a fault, the data added to the faulty line and the output level of an LPF 11 exceeds the normal value. Thus the output of a NAND gate 13 has a high level and this high output is inputted to a flip-flop 16. Thus an abnormality detection signal is outputted to the circuit 7 which instructs the selector 8 to select the system to be received and then to switch the circuit 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus type transmission device,
In particular, it relates to a bus type duplex transmission device.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional bus type transmission device. In FIG. 9, 1 is a transmission line, 2a and 2b are terminators composed of terminating resistors, 3a and 3n are nodes, and 4a and 4n are transmitters (TX). ) 5a and 5n are receivers (RX).
Each node has a transmitter (TX) and a receiver (RX),
Transmission is performed via a common transmission line.

[0003]

When a node fails and continues to send abnormal data or the like, another node fails and abnormal data collides, making it impossible to communicate with the other party.
In other words, the failure of one node caused the entire network to go down. Therefore, in the case of the bus type transmission line, a failure at one location may spread to the whole, and in the case where the reliability is required, it is necessary to duplicate the transmission line.

As a matter of course, if the transmission device is duplicated, the cost is also doubled, and the hardware and software for data processing by the duplicated transmission device are complicated, which naturally raises the cost.

The present invention has been made in view of the above problems, and an object thereof is to simultaneously transmit data to a duplicated bus type transmission line and take in data from a normal system, thereby reducing the cost and improving the performance. Another object of the present invention is to provide a redundant bus type transmission device.

[0006]

In order to achieve the above-mentioned object, a bus type duplex transmission apparatus of the present invention connects a node having a transmission circuit and a reception circuit respectively connected to a duplexed bus type transmission line. In the transmission device, means for simultaneously transmitting transmission data to each of the bus type transmission lines to the node, abnormality detection circuit means for discriminating between an abnormal transmission line system and a normal transmission line system, It is constituted by means for fetching data from a normal transmission line system based on the judgment of the abnormality detection circuit means. Further, the node is provided with means for current-driving each of the bus type transmission lines.

[0007]

[Function] Two bus type transmission lines are provided, and each transmission line has a transmission / reception circuit and an abnormality detection circuit. Transmitted data is transmitted to both systems at the same time. By duplicating the transmission line by taking in the data from a different system.

Further, in order to facilitate the monitoring of the abnormality on the transmission line, the transmission line is current-driven, and it is possible to detect a collision, an open, a short circuit or the like on the transmission line.

[0009]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows a bus-type duplex transmission device to which the present invention is applied. Nodes 3a, 3b, ... 3n are connected to the A-system transmission line 1a and the B-system transmission line 1b, respectively. Are configured as shown in FIG.

That is, as shown in FIG. 1, in each node, the transmission lines 1a and 1b are respectively connected to the transmitters 4a and 4b.
4b and the receivers 5a and 5b are connected, and the abnormality detection circuits 6a and 6 are respectively provided at the input stages of the receivers 5a and 5b.
b is connected. A system selector 8 is connected to the output stages of the receivers 5a and 5b, and a system switching control circuit 7 is connected to the output stages of the abnormality detection circuits 6a and 6b.

In the apparatus of FIG. 1, the transmission data are A and B.
It is sent to both systems at the same time. Each receiver has a transmission path abnormality detection unit, and the system switching control circuit 7 causes the system selector 8 to select the system to be received based on the transmission path abnormality information.

FIG. 3 shows a circuit configuration of the abnormality detecting section 6a (6b). Reference numeral 9 is a current converter for converting transmission data into a current signal, and 10 is carrier detection (connected to the input stage of the receiver 5a). The CD) circuit 11 is a low-pass filter (LPF) also connected to the input stage of the receiver 5a. 1
2 is a comparator that receives the output signal of the LPF 11 and the threshold voltage VTH; 13 is a NAND gate that receives the output signal of the CD detection circuit 10 and the output signal of the comparator 12; 14 is an OR gate; 15 is a NOT gate; 16 is an OR gate It is a flip-flop that receives the output of 14 and the output of the NOT gate 15.

In the abnormality detection circuit of FIG. 3, the transmission data is converted into a current by the current converter 9 and is current-driven.
The CD detection is the detection of the received carrier, and as shown in FIG. 4, the CD is detected when the device is normal. The LPF 11 detects the level, and the level detection signal of the LPF 11 and the threshold signal are compared by the comparator 12. The output signal of the comparator 12 and the CD detection signal of the CD detector are input to the NAND gate 13. The OR gate 14 receives the output signal of the NAND gate 13 as one input, and the output signal of the OR gate 14 is input to the flip-flop 15. Further, transmission data is input to the NOT gate 15, an output signal of the NOT gate 15 is input to the flip-flop 16, and an output signal of the flip-flop 16 becomes an abnormality detection signal and is also input to the OR gate 14.

When data collides on the transmission line, the data is added because the transmission line is current-driven as shown in FIG. Therefore, the output level of the LPF 11 also exceeds the normal value, the output of the comparator 11 becomes low level “0”, and the output of the NAND gate 13 becomes high level. The output of the NAND gate 13 is input to the flip-flop 16 through the OR gate 14, and the flip-flop 1
6 outputs an abnormality detection signal.

When the transmission line is short-circuited, there is no CD detection as shown in FIG. 6, so only the output of the comparator 12 is input to the NAND gate 13.
The output of 3 becomes high level, this output signal is input to the flip-flop 16 through the OR gate 14, and the abnormality detection signal is output from the flip-flop 16.

When the transmission line is open, the transmission is current-driven, so that the transmission level becomes abnormally high and the output of the comparator 12 is at a high level as shown in FIG.
Since there is no D detection signal, the output of the NAND gate 13 becomes high level. The high level output signal of the NAND gate 13 is input to the flip-flop 16 and the flip-flop 1
6 outputs an abnormality detection signal.

In the abnormality detecting unit of FIG. 3, the flip-flop 16 is an error latch, and if the flip-flop 16 is abnormal at a high level, the flip-flop 16 is cleared by abnormality detection clear before transmission is started. The output signal of the flip-flop 16 becomes the low level "L" only when the CD detection signal of the CD detection circuit 10 is at the high level "H" and the output signal of the comparator 12 is at the high level "H", and is otherwise at the high level. It becomes "H". Further, unless the output signal of the flip-flop 16 once becomes the high level "H" by the OR gate 14, it is cleared, the flip-flop 16 outputs the high level signal and detects the abnormality.

In the bus type duplex transmission apparatus of FIG. 1, system switching is executed by the algorithm of FIG. That is, as shown in FIG. 8, for example, system A is selected in step S1, and abnormality detection is cleared in step S2. After clearing the abnormality detection, transmission is performed in step S3. Next, in step S4, it is determined whether or not the power transmission system path is normal. If the power transmission path is normal, the process returns to step S2. If the power transmission system path is normal, the process proceeds to step S5 to determine whether both systems are abnormal. If both systems are abnormal, step S5 is performed.
It progresses to 7 and determines that an abnormality has occurred. If neither system is abnormal in step S5, the process proceeds to step S6, the systems are switched, and then the process returns to step S2. In this way, even if a transmission path abnormality occurs, a normal system is selected and transmission is performed.

[0020]

As described above, the present invention is capable of protecting a bus type transmission device from an abnormality such as a collision, an open or a short of transmission data on a transmission line, thereby improving reliability and Compared with the case of duplication including the transmission device, the cost of hardware and software is not increased, and an inexpensive bus type duplication transmission device can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a bus type duplex transmission device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a bus-type duplex transmission device to which the present invention is applied.

FIG. 3 is a block diagram of an abnormality detection circuit of a bus type duplex transmission device according to an embodiment of the present invention.

FIG. 4 is a detection timing chart of the abnormality detection circuit of FIG.

5 is a detection timing chart of the abnormality detection circuit of FIG.

FIG. 6 is a detection timing chart of the abnormality detection circuit of FIG.

7 is a detection timing chart of the abnormality detection circuit of FIG.

FIG. 8 is an operation flowchart showing a system switching algorithm of the bus type duplex transmission device according to the embodiment of the present invention.

FIG. 9 is a block diagram showing a schematic configuration of a conventional transmission device.

[Explanation of symbols]

 1a, 1b ... Bus type transmission path 3a, 3b ... 3n ... Nodes 4a, 4b ... Transmitter 5a, 5b ... Receiver 6a, 6b ... Abnormality detection circuit 7 ... System switching control circuit 8 ... System selector 9 ... Current converter 10 ... Carrier detector 11 ... Low-pass filter 12 ... Comparator 13 ... NAND gate 14 ... OR gate 15 ... Not gate 16 ... Flip-flop

Claims (2)

[Claims] 1. A transmission device comprising a node having a transmission circuit and a reception circuit, which are respectively connected to a duplicated bus type transmission line, in which transmission data is transmitted to the node and transmission data is transmitted to each of the bus type transmission lines. Of the abnormal transmission line system and the abnormal transmission line system for distinguishing between the abnormal transmission line system and the normal transmission line system, and means for taking in data from the normal transmission line system based on the judgment of the abnormality detection circuit unit. A bus-type duplex transmission device characterized in that 2. The bus-type duplex transmission device according to claim 1, wherein the node is provided with means for driving the respective bus-type transmission lines with current.