WO2014176864A1

WO2014176864A1 - Line concentration method for multi-channel isolation of can bus

Info

Publication number: WO2014176864A1
Application number: PCT/CN2013/084098
Authority: WO
Inventors: 刘宏博; 郑玉平; 周华良; 邹志杨; 胡钰林
Original assignee: 国电南瑞科技股份有限公司
Priority date: 2013-04-28
Filing date: 2013-09-24
Publication date: 2014-11-06
Also published as: CN103220199B; CN103220199A

Abstract

A line concentration method for multi-channel isolation of a CAN (Controller Area Network) bus is disclosed, the method comprising the following steps: detecting the electrical level of a bus on the local side of the CAN bus in real time; judging the state of the electrical level of the bus on the local side of the CAN bus; if the electrical level of the bus on the local side of the CAN bus is in a dominant state, limiting the rotation of the dominant state of the opposite side of the CAN bus; if the electrical level of the bus on the local side of the CAN bus turns into a recessive state, carrying out delaying, continuously limiting dominant signals forwarded from the opposite side of the CAN bus until the end of the delaying; and detecting whether the CAN bus enters a self-locking state in real time, if the CAN bus enters the self-locking state, releasing the self-locking state. By using the line concentration method for the multi-channel isolation of the CAN bus of the present invention, the isolation and the interconnection of the multi-channel CAN buses and the interconnection of optical fibers of the two lateral CAN buses are achieved, the forwarding is avoided, the transparent transmission of the data is high, the delaying is short, the instantaneity of industrial control is achieved, and the design cost and the bus power consumption are further lowered, so that the line concentration method will have a good applying prospect.

Description

CAN bus multi-channel isolation method

Technical field

The invention belongs to the technical field of industrial control field bus communication, and particularly relates to a line gathering method for realizing multi-way isolation of CAN bus.

Background technique

At present, CAN (Controller Area Network) fieldbus is widely used in industrial automation, automotive electronics, building automation, power automation and security, and has become the main communication means in these industries. CAN bus is connected by cable bus. However, in the actual application process, due to the complex environment of the wiring site and the complex network topology, it is often necessary to use a variety of connection methods, such as interconnecting the remote side buses with optical fibers, or interconnecting multiple regional buses. When interconnected by the above method, if the direct interconnection without the measure causes the self-locking of the CAN bus, the normal communication cannot be performed. At present, the above problem is solved by adding a smart bus (HUB) of the CAN bus, and the smart hub is The CAN data of each side CAN bus is decoded and forwarded, which can effectively solve the self-locking problem of the CAN bus, and allow the rates of the CAN buses on different sides to be different. However, due to the intelligent hub forwarding, the data has a large delay (more than 2). Milliseconds), which reduces the data on the CAN bus The throughput rate and data transmission rate cannot be used for monitoring systems with strong real-time requirements.

Summary of the invention

The object of the present invention is to overcome the problems in the prior art. The present invention provides a CAN bus multi-channel isolation method, which satisfies the isolation interconnection of multiple CAN buses and the optical interconnection of CAN buses on both sides, and the CAN bus can directly Interconnection, no need to forward, high data transparent transmission, short data transmission delay, well meet the real-time requirements of industrial control, reduce design cost and bus power consumption, have good response Use the foreground.

In order to achieve the above object, the technical solution adopted by the present invention is:

A CAN bus multi-channel isolation method, characterized in that: the following steps are included: Step (1) Real-time detection of the bus level on the side of the CAN bus;

Step (2) Judging the state of the bus level on the side of the CAN bus;

Step (3) if the level of the current side of the CAN bus is dominant, limiting the dominant state rotation of the opposite side of the CAN bus;

Step (4) If the level of the current side of the CAN bus changes to a recessive state, delay is performed to continue limiting the dominant signal forwarded by the opposite side of the CAN bus until the delay ends;

Step (5) Real-time detection of whether the CAN bus enters the self-locking state. If the CAN bus enters the self-locking state, the self-locking state is released until the delay of the same time as the step (4) ends.

The foregoing CAN bus multi-channel isolation collecting method is characterized in that: (2) determining the state of the bus level on the side of the CAN bus, including the network name of the local port of the CAN bus and the corresponding high and low levels. The network name includes the receiving end and the transmitting end.

The foregoing CAN bus multi-channel isolation method is characterized in that: (3) limiting the method of the dominant state rotation on the opposite side of the CAN bus, including the following steps,

(1) The opposite side of the CAN bus is dominant, and the low-level output of the receiving terminal R on the opposite side of the CAN bus is controlled by the logic gate;

(2) The output low side of the opposite side of the CAN bus passes through the extended edge circuit to limit the transmitting end T of the CAN bus to the high level, and allows the low level of the opposite side of the CAN bus to pass through the side of the CAN bus. The transmitting terminal T turns the CAN bus to the dominant state.

The aforementioned CAN bus multi-channel isolation method is characterized in that: step (4) continues to limit The dominant signal forwarded by the opposite side of the CAN bus until the end of the delay is when the dominant side of the CAN bus disappears, the falling edge signal is output through the logic gate, and is applied to the input end of the lower edge extension circuit. The lower edge extension circuit continues to limit the transmit terminal T on the opposite side of the CAN bus to a high level until the delay of the next skip signal ends.

The above-mentioned CAN bus multi-channel isolation method is characterized in that: the criterion of the self-locking state of the step (5) is that the level of the current side and the opposite side of the CAN bus are both low level, and the self-locking is released. The steps of the state are as follows.

(1) When the level of the current side and the opposite side of the CAN bus are both low, the low level is output to the high level through the NAND gate;

(2) The output high level is respectively passed through the following edge extension circuit, so that the transmitting end T of the CAN bus side and the opposite side becomes a high level; at the same time, the self-locking state disappears, and the transmitting side T of the present side and the opposite side is maintained. High level.

(3) When the receiving side of the CAN bus and the receiving side of the opposite side are turned to a high level, the output is a lower edge signal, which is respectively applied to the input end of the lower edge extension circuit, so that the transmitting side T of the CAN bus side and the opposite side are limited. It is high until the end of the delay, and the self-locking state is completed.

The foregoing method for collecting multiple lines of the CAN bus is characterized in that: the delay time of the delay according to the step (4) is greater than the recessive state of the opposite side of the CAN bus to the rotation of the side of the CAN bus. Transmission delay time.

The invention has the beneficial effects of: realizing optical fiber interconnection, multiple CAN field bus isolation interconnection; data transparent and no delay transmission, meeting real-time requirements; adapting to various complex network topologies, greatly reducing cost and power consumption, CAN The bus can be directly interconnected without forwarding, the data transparent transmission is high, the data transmission delay is short, the real-time requirements of industrial control are well met, and the design cost and bus function are also reduced. Consumption, has a good application prospects.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a CAN bus multi-channel isolation system of the present invention.

detailed description

The invention will now be further described in conjunction with the drawings of the specification.

The CAN bus multi-channel isolation concentrating method of the invention can realize optical fiber interconnection, multiple CAN field bus isolation interconnection, data transparent and no delay transmission, meet real-time requirements; adapt to various complex network topologies, and greatly reduce Cost and power consumption, CAN bus can be directly interconnected, no need to forward, data transparent transmission is high, data transmission delay is short, it satisfies the real-time requirements of industrial control, and reduces design cost and bus power consumption, including the following steps ,

Step (1) Real-time detection of the bus level on the side of the CAN bus;

Step (2) determining the state of the bus level on the current side of the CAN bus, and determining the state of the bus level on the local side of the CAN bus, including the network name of the port on the local side of the CAN bus and the corresponding high and low levels, the network name including Receiver and sender;

Step (3) If the level of the current side of the CAN bus is dominant, the dominant state of the opposite side of the CAN bus is limited, and the dominant state of the opposite side of the CAN bus is limited as follows:

1) The opposite side of the CAN bus is a dominant state, and the receiving terminal R of the opposite side of the CAN bus is controlled to output a low level through a logic gate;

2) The output low level of the opposite side of the CAN bus passes through the extended edge circuit to limit the transmitting end T of the CAN bus to the high level, and allows the low level of the opposite side of the CAN bus to be transmitted through the CAN bus. Terminal T, the local side of the CAN bus is turned into a dominant state;

Step (4) If the level of the current side of the CAN bus changes to a recessive state, delay is performed and the limit is continued. The dominant signal forwarded by the opposite side of the CAN bus until the end of the delay. When the dominant side of the CAN bus disappears, the falling edge signal is output through the logic gate, applied to the input of the lower edge extension circuit, and passes through the lower edge. The extension circuit continues to limit the transmitting terminal T on the opposite side of the CAN bus to a high level until the delay of the falling edge signal ends;

Step (5) Real-time detection of whether the CAN bus enters the self-locking state. If the CAN bus enters the self-locking state, the self-locking state is released, until the delay of the same time as the step (4) ends, the criterion of the self-locking state is The level of the current side and the opposite side of the CAN bus are both low, and the steps of releasing the self-locking state are as follows.

1) When the level of the current side and the opposite side of the CAN bus are both low, the low level is output high through the NAND gate;

2) The output high level is respectively passed through the extension circuit to make the transmitting end T of the CAN bus and the opposite side of the CAN bus become high level; at the same time, the self-locking state disappears, and the transmitting end T of the present side and the opposite side are kept high. Level.

3) When the receiving side of the CAN bus and the receiving end of the opposite side are turned to a high level, the output is a lower edge signal, which is respectively applied to the input end of the lower edge extension circuit, so that the transmitting end T of the CAN bus side and the opposite side are limited to High level until the end of the delay, the self-locking state is completed.

The delay time for performing the delay is greater than the delay time of the opposite side of the CAN bus to the transmission delay time of the CAN bus to the side of the side.

In the following, in conjunction with an embodiment, a detailed description of the CAN bus multi-channel isolation method of the present invention is shown. As shown in FIG. 1, the CAN bus multi-channel isolation line system includes

1) 1CAN, 2CAN transceiver, the bus of this CAN transceiver has two states, dominant and recessive state; when the transmitter is low, the bus is dominant; when the bus is dominant, receive The terminal is low; however, the CAN transceiver is self-receiving, which is the cause of the bus being self-locking; 2) Digital isolator: For anti-interference, the logic does not change, but there is a certain delay. The invention needs to use a small delay digital isolator.

It can be seen from Fig. 1 that the dominantness of the CAN bus 1# side (herein referred to as the dominant only due to the far side) is judged as the receiving end 1R=0, the transmitting end 1T=1; the dominant side of the CAN bus 2# side (This refers to the dominant only due to the local side.) The criterion is that the receiving end 2R=0, the transmitting end 2T=1 _{; the} bus self-locking state criterion is 1R, 1T, 2R, 2T=0;

When the bus of the 1# side (also the 2# side) of one side is detected to enter the dominant state (1R=0, 1T=1), the AND gate U3 outputs 1 and the lower edge extension circuit U4 outputs 1 , the output 1T is forced to 1, which avoids 2Τ=0 due to 1R=0, and 2R=0 after delay by 2CAN transceiver, and reverses to 1T=0 via U2, thus avoiding bus self-locking ;

When the bus on the 1# side returns to recessive, 2R is still 0 at this time. For this reason, 1T still needs to be forced to maintain 1 (the pulse signal with the lower edge delay of Twl generated by U4:), until the 1R signal delays Go to 2R, at this moment the dominant state on the 1# side disappears in the whole domain, and 1T returns to the state 2R on the bus 2# side (if 2R=0, only the bus 2# side is dominant).

Considering that the power-on or interference may cause the CAN bus to enter the self-locking state, to prevent this, when 1R, 1T, 2R, 2T=0, the NAND gate U9 outputs 1 to make the NAND gates U3 and U7 output also 1 Then, 1T and 2Τ are 1 and the NAND gate U9 outputs 0, so that the output of the NOT gate U3 and U7 changes from 1 to 0, which triggers the lower edge extension circuits U4 and U8 to generate pulses with lower edge delays of Twl and Tw2, respectively. The signal, thus forcing 1T, 2Τ to 1, releases the self-locking state until the erroneous dominant state disappears in the entire domain.

The delay width of the lower edge extension circuit U4, U8 module depends on the path of the signal in Figure 1, taking the 1# side as an example, 1R from the low to high level as the starting point, and the delay from the OR gate U6 to 2T , then delayed by the digital isolator to the transmitter of the 2CAN transceiver, and then delayed by the transmitter of the 2CAN transceiver to the total CAN Line 2# side, and then the delay of the 2# side through the 2CAN transceiver's receiver to 2R is up, the above path time is actually the sum of the delay time of the signal flowing through each device, select the appropriate device, delay time The sum can be less than 250 nS, the delay time of the general delay is greater than the above path time, and also less than half of the BIT bit time of the CAN. Specifically, when the maximum 1MHz of the CAN bus is selected, the delay time can be 450nS, which is relative. There is a large delay (more than 2 milliseconds) in the traditional CAN bus data transmission, which reduces the data throughput rate and data transmission rate of the CAN bus, and thus cannot be used for a monitoring system with strong real-time requirements.

The basic principles, main features and advantages of the present invention have been shown and described above. It should be understood by those skilled in the art that the present invention is not limited by the foregoing embodiments, and that the present invention is only described in the foregoing embodiments and the description of the present invention, without departing from the spirit and scope of the invention. Various changes and modifications are intended to fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and their equivalents.

Claims

claims

1. The CAN bus multi-channel isolation collection method is characterized by: including the following steps: (1) Real-time detection of the bus level on the local side of the CAN bus;

Steps (2) Determine the status of the bus level on this side of the CAN bus;

Step (3) If the level on this side of the CAN bus is in the dominant state, limit the dominant state rotation on the other side of the CAN bus;

Step (4) If the level on this side of the CAN bus changes to a recessive state, perform a delay and continue to limit the dominant signal forwarded from the opposite side of the CAN bus until the delay ends;

Step (5) Detect in real time whether the CAN bus enters the self-locking state. If the CAN bus enters the self-locking state, release the self-locking state until the delay of the same time as step (4) ends.

2. The CAN bus multi-channel isolation collection method according to claim 1, characterized in that: Step (2) Determining the status of the bus level on the local side of the CAN bus includes the network name of the port on the local side of the CAN bus and the corresponding High and low levels, the network name includes the receiving end and the sending end.

3. The CAN bus multi-channel isolation collection method according to claim 1, characterized in that: Step (3) The method of limiting the dominant state rotation of the opposite side of the CAN bus includes the following steps:

(1) The opposite side of the CAN bus is in a dominant state, and the receiving end R on the opposite side of the CAN bus is controlled by a logic gate to output a low level;

(2) The low level output of the opposite side of the CAN bus passes through the lower edge extension circuit, limiting the sending terminal T on the opposite side of the CAN bus to a high level, and at the same time allowing the low level output of the opposite side of the CAN bus to pass through the local side of the CAN bus. The sending end T turns the CAN bus side into a dominant state.

4. The CAN bus multi-channel isolation gathering method according to claim 1, characterized in that: step (4) continues to limit the dominant signal forwarded from the opposite side of the CAN bus until the delay is completed. When the dominance of the opposite side of the CAN bus disappears, the lower edge signal is output through the logic gate and applied to the input end of the lower edge extension circuit U4 module. The lower edge extension circuit continues to limit the sending end T of the opposite side of the CAN bus to high. level until the delay of the next edge signal ends.

5. The CAN bus multi-channel isolation collection method according to claim 1, characterized in that: the criterion of the self-locking state in step (5) is that the levels of the local side and the opposite side of the CAN bus are both low. level, the steps to release the self-locking state are as follows:

(1) When the levels on this side and the opposite side of the CAN bus are both low level, the low level is output to high level through the NOR logic gate;

(2) The output high level passes through the lower edge extension circuit respectively, causing the sending end T on this side and the opposite side of the CAN bus to become high level; at the same time, the self-locking state disappears, and the sending end T on this side and the opposite side of the CAN bus is maintained. T becomes high level;

(3) When the receiving end of the CAN bus on this side and the opposite side turns to high level, the output is a lower edge signal, which is applied to the input end of the lower edge extension circuit respectively, so that the sending end of the CAN bus on this side and the opposite side T limit It remains high until the delay ends, and the self-locking state is released.

6. The CAN bus multi-channel isolation gathering method according to claim 1, characterized in that: the delay time of the delay in step (4) is greater than the recessive state of the opposite side of the CAN bus to the CAN bus. The transmission delay time in the roundabout on this side of the bus.