CN111478842A - High-speed data transmission system and method - Google Patents
High-speed data transmission system and method Download PDFInfo
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- CN111478842A CN111478842A CN202010294307.2A CN202010294307A CN111478842A CN 111478842 A CN111478842 A CN 111478842A CN 202010294307 A CN202010294307 A CN 202010294307A CN 111478842 A CN111478842 A CN 111478842A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/4013—Management of data rate on the bus
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L12/40006—Architecture of a communication node
- H04L12/40013—Details regarding a bus controller
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
- H04L12/40—Bus networks
- H04L2012/40208—Bus networks characterized by the use of a particular bus standard
- H04L2012/40215—Controller Area Network CAN
Abstract
The invention provides a high-speed data transmission system and a method, comprising the following steps: two pairs of data buses, two arbitration lines and a plurality of communication nodes; each arbitration line is used for controlling different data buses respectively, each arbitration line carries out transmission by taking an arbitration frame as a unit, each data bus carries out transmission by taking a data frame as a unit, each arbitration frame selects a winning communication node, and the winning communication node obtains the use right of the next data frame of the target data bus. The invention can realize the requirements of high-speed, reliable and real-time communication among a plurality of communication nodes.
Description
Technical Field
The present invention relates to the field of data transmission, and more particularly, to a high speed data transmission system and method.
Background
A CAN (Controller Area Network) bus has been widely used in the fields of automobile application, industrial automation, and the like because of its advantages of high reliability, real-time performance, and the like.
The CAN bus only comprises a pair of differential signal lines, adopts serial data transmission and has simple structure; the method supports multi-master communication, namely each node device can actively initiate data communication to other node devices on the network at any time, and the communication sequence is determined according to the priority of the identifier of each node device; when a plurality of node devices simultaneously initiate communication, the avoidance priority with low priority is high. However, the bus rate is limited, and is up to 1Mbps (the communication distance is less than 40 meters), and the data frame of the CAN bus CAN transmit at most 8 bytes of effective data each time, which cannot meet the design requirement of large data volume high-speed communication among a plurality of node devices. In addition, when there are many node devices hanging on the bus, communication conflicts are easy to occur, only one node device is allowed to obtain the right of use of the bus for data transmission by arbitration each time, and other node devices have to wait, so that the bus rate is limited.
Disclosure of Invention
The invention aims to provide a high-speed data transmission system and a high-speed data transmission method, which can realize the requirements of high-speed and real-time communication among a plurality of communication nodes by utilizing a high-speed data bus under the multipoint interconnection application occasion and have high transmission efficiency and high reliability.
The technical scheme provided by the invention is as follows:
a high speed data transmission system comprising: the data bus is transmitted by taking a data frame as a unit; the arbitration lines are respectively used for controlling the election function of the data sending rights of different data buses, wherein the arbitration lines transmit by taking arbitration frames as units, the transmission time of the arbitration frames is the same as that of the data frames, and each arbitration frame is used for transmitting the identifier of the winner communication node; the communication nodes are respectively connected in parallel and hung on the data buses and the arbitration line; each communication node includes: the arbitration interface module is used for sending the identifier of the arbitration interface module to an arbitration line; the data sending module is used for sending own data to the data bus; the control module is used for selecting an arbitration line when detecting that the arbitration interface module has a data transmission requirement, and controlling the arbitration interface module to transmit the identifier of the arbitration interface module to the arbitration line in the current arbitration time period of the current arbitration frame; and when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and controls the data transmission module to transmit own data to a target data bus in the next data frame.
Further preferably, the system clock is in a quasi-synchronous manner.
Further preferably, the arbitration interface module is further configured to send its own identifier to the arbitration lines according to a preset phase difference, wherein a deviation between the preset phase differences of the two arbitration lines is located at (0 °,180 °).
Further preferably, the control module is further configured to dynamically select one arbitration line according to the idle rates of different arbitration lines when it is detected that the control module has a data transmission requirement.
Further preferably, the arbitration interface module is further configured to send an identifier composed of a plurality of symbols onto the arbitration bus, wherein when consecutive same symbols are sent, the identifier is sent with a different encoding result from a previous symbol.
The invention also provides a high-speed data transmission method, which comprises the following steps: in the current arbitration frame, a communication node with a data transmission requirement selects an arbitration line and transmits an identifier of the communication node to the arbitration line; and when the identifier is detected to be successfully sent, the communication node is a winning communication node of the current arbitration frame, and sends own data to a target data bus in the next data frame, wherein the target data bus is a data bus controlled by the arbitration frame.
Further preferably, the method further comprises the following steps: the system clock adopts a quasi-synchronous mode.
Further preferably, the sending of the own identifier to the arbitration line includes: the own identifier is sent to the arbitration lines with a predetermined phase difference, wherein the deviation between the predetermined phase differences of the two arbitration lines is located at (0 °,180 °).
Further preferably, the selecting an arbitration line by the communication node having a data transmission requirement includes: the communication node with the data transmission requirement dynamically selects one arbitration line according to the idle rate of different arbitration lines.
Further preferably, the sending the own identifier to the arbitration line further includes: an identifier consisting of a plurality of symbols is sent onto the arbitration line, wherein when consecutive identical symbols are sent, the transmission is performed with a different encoding result from the previous symbol.
The high-speed data transmission system and the high-speed data transmission method provided by the invention can bring at least one of the following beneficial effects:
1. according to the invention, the arbitration line is separated from the data bus, so that the transmission rate of the data bus can be improved; on the premise of ensuring the transmission rate of the data bus, the transmission rate of the arbitration line is reduced to improve the reliability of the system.
2. According to the invention, different arbitration lines are used for controlling different data buses, so that the transmission delay caused by collision can be reduced, and the transmission efficiency of the buses can be improved; each communication node can dynamically select arbitration lines according to the idle rates of different arbitration lines, so that the collision probability of collisions can be further reduced, and the transmission efficiency of the bus is improved.
3. The invention can support the blind plugging of the bus connector by respectively driving the two arbitration lines by the system clock in a quasi-synchronous mode or a synchronous mode and according to the preset phase difference.
4. According to the invention, when the same symbol is continuously transmitted, the encoding results of the symbol in different encoding modes are alternately transmitted, so that the decoding reliability, the fault identification capability of the system and the anti-interference capability of the system are improved.
Drawings
The above features, technical features, advantages and modes of realisation of a high speed data transmission system and a high speed data transmission method will be further described in the following, in a clearly understandable manner, with reference to the accompanying drawings, which illustrate preferred embodiments.
FIG. 1 is a schematic diagram of one embodiment of a high speed data transmission system of the present invention;
FIG. 2 is a flow chart of one embodiment of a high speed data transmission method of the present invention;
FIG. 3 is a flow chart of another embodiment of a high speed data transmission method of the present invention;
FIG. 4 is a flow chart of another embodiment of a high speed data transmission method of the present invention;
fig. 5 is a schematic voltage diagram of two arbitration lines respectively driven with a predetermined phase difference according to another embodiment of a high-speed data transmission method of the present invention.
The reference numbers illustrate:
100. the system comprises an arbitration interface module, a control module and a data sending module, wherein the arbitration interface module comprises 200.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will be made with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically illustrated or only labeled. In this document, "one" means not only "only one" but also a case of "more than one".
In one embodiment of the present invention, as shown in fig. 1, a high-speed data transmission system includes: the data bus is transmitted by taking a data frame as a unit; the arbitration lines are respectively used for controlling the election function of the data sending rights of different data buses, wherein the arbitration lines transmit by taking arbitration frames as units, the transmission time of the arbitration frames is the same as that of the data frames, and each arbitration frame is used for transmitting the identifier of the winner communication node; and the communication nodes are respectively connected in parallel and hung on the data buses and the arbitration line.
Specifically, an arbitration frame and a data frame on the CAN bus are multiplexed on the same bus in a time-sharing manner, and the arbitration frame limits the transmission rate of the data frame. In order to improve the transmission rate of the data bus, in the invention, the arbitration line is separated from the data bus, arbitration information is sent on the arbitration line, data information is sent on the data bus, the data bus can adopt a high-speed channel coding transmission scheme completely different from the arbitration line, the data bus has a higher symbol modulation rate to meet the high-speed transmission requirement, and the arbitration line has a lower symbol modulation rate to ensure the arbitration reliability.
The two arbitration lines are independently coded relative to the power supply and the ground respectively, so that the two arbitration lines can respectively send different identifiers, and the transmission rate of the identifiers is doubled.
The arbitration lines are transmitted according to arbitration frames, each arbitration frame is the identifier sending time of each communication node, the communication nodes are arbitrated according to the priority of the identifiers when colliding, the arbitration lines arbitrate the identifiers of the communication nodes participating in data sending right election of the arbitration frames, and finally, only the identifiers with high priority are presented on the arbitration lines, and the communication node corresponding to the identifier with high priority is the winning communication node of the arbitration frame.
The data bus is transmitted according to data frames, the transmission time of one data frame is the same as that of one arbitration frame, but the data volume transmitted in the same time is different, and the data volume of the data frame is larger than that of the arbitration frame, so that the transmission rate of the data bus is high.
At each arbitration frame, the winning communication node will obtain the transmission right for the next data frame for transmitting a frame of data. The data frame comprises an identifier of the receiving equipment, so that the receiving equipment can identify whether the data is sent to the receiving equipment, and if so, the data is received; otherwise, the process is abandoned.
Each communication node includes:
an arbitration interface module 100 for sending its own identifier to an arbitration line;
a data transmitting module 300 for transmitting its data to a data bus;
the control module 200 is configured to select an arbitration line when it is detected that there is a data transmission requirement for the arbitration module, and control the arbitration interface module to transmit an identifier of the arbitration interface module to the arbitration line in a current arbitration frame; and when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and controls the data transmission module to transmit own data to a target data bus in the next data frame.
Specifically, each communication node has a unique identifier for identifying itself, and the identifier is composed of one or more symbols. Each communication node must first send its own identifier on the arbitration line before sending data, and can only send on the data bus after the own identifier is successfully sent on the arbitration line. Since the system has two arbitration lines each controlling one pair of data buses and two pairs of data buses, and different arbitration lines controlling different data buses, each communication node must first select one arbitration line before transmitting data and then transmit its own identifier on that arbitration line. There are various ways to select the arbitration line, one arbitration line can be selected fixedly, or the arbitration line can be selected dynamically each time an identifier is sent; there are many ways to dynamically select the arbitration line, such as random selection, or to optimize the arbitration line with high idleness rate according to the idle condition of the arbitration line to reduce the probability of collision.
After the communication node sends a bit symbol of the identifier, monitoring the symbol on the arbitration line; when the symbol on the arbitration line is different from the symbol transmitted by the communication node, the transmission of the identifier is considered to be failed, and the transmission of the subsequent symbol of the identifier is stopped; when the symbol on the arbitration line is the same as the symbol sent by the communication node, indicating that the communication node successfully sends the one-bit symbol of the identifier; if there are more symbols to send, continuing to send the next symbol of the identifier; when the communication node successfully transmits all symbols of the identifier, the transmission of the identifier is considered successful.
When a plurality of communication nodes send identifiers simultaneously, the communication nodes which can correctly send the identifiers to the arbitration line obtain the arbitration success of the current arbitration frame to become the winner communication nodes, obtain the use right of the next data frame of the target data bus, and simultaneously, the arbitration is finished. The target data bus refers to the data bus controlled by the arbitration line. At the next arbitration frame, all devices again participate in arbitration.
Because two pairs of data buses exist, at most two communication nodes can be contended in each arbitration frame to obtain the use right of the data buses, and therefore the data transmission rate of the system is improved.
In another embodiment of the present invention, as shown in fig. 1, a high speed data transmission system includes:
on the basis of the previous embodiment, add: the system clock of the high-speed data transmission system adopts a quasi-synchronous mode.
The function of each communication node is replaced by:
each communication node includes:
the arbitration interface module 100 is configured to send its own identifier to one arbitration line according to a predetermined phase difference, wherein the deviation between the predetermined phase differences of the two arbitration lines is (0 °,180 °).
And a data sending module 300, configured to send its data to the data bus.
The control module 200 is configured to dynamically select an arbitration line according to the idle rates of different arbitration lines when it is detected that the arbitration module has a data transmission requirement, and control the arbitration interface module to transmit an identifier of the arbitration interface module to the arbitration line in a current arbitration frame; and when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and controls the data transmission module to transmit own data to a target data bus in the next data frame.
Specifically, the plesiochronous mode is to recover a clock signal and a positioning clock signal through a deviation between preset phase differences used by a bus and to allow the clock signal to serve as a system reference clock. The system is provided with high-precision clock samplers at each communication node, and the error between the signals of the clocks is within the acceptable range of the system. Therefore, although the system has a uniform clock signal, no extra wiring harness is provided for transmitting the clock signal, so that the synchronization mode is not true synchronization strictly, and is called as quasi-synchronization.
The synchronous mode means that the system has a uniform reference clock, and each communication node transmits and receives data based on the uniform reference clock.
The arbitration line idleness can be calculated according to the number of times the arbitration line is idled for a certain time, for example, arbitration line 1, 50 arbitration frames out of 100 consecutive arbitration frames do not have any communication node sending an identifier to the arbitration line, indicating that the idleness is 50%; arbitration line 2, 10 arbitration frames out of 100 consecutive arbitration frames do not have any communication node sending an identifier onto the arbitration line, indicating that the idle rate is 10%; according to the idle rate, the arbitration line 2 is busy than the arbitration line 1, when a certain communication node has a data transmission demand, the arbitration line with high idle rate is preferentially selected, namely the arbitration line 1 is selected, the probability of collision is low, and the use right of the data bus can be more easily obtained.
The preset phase difference of the arbitration line refers to a phase difference of a transmission time point of the communication node from a clock signal (for example, a rising edge of one clock cycle) of the communication node when transmitting each symbol of the identifier to the arbitration line. The transmission time point at which the identifier is transmitted to the corresponding arbitration line can be determined based on the preset phase difference and the clock signal of the present communication node.
Each communication node of the system is connected to a system bus by a bus connector that includes two pairs of data buses and two arbitration lines. When the signal lines included in the bus connector are symmetrically arranged (for example, the data bus 1 arbitration line 2 data bus 2), the bus connector is easy to be inserted reversely in operation, and is similar to the data line of an apple mobile phone, so that the system is required to support the insertion and extraction of the bus connector in any direction, otherwise, the wrong insertion is required to be avoided through the structure of the bus connector.
When the two arbitration lines are provided with different preset phase differences and the deviation between the preset phase differences of the two arbitration lines is between (0 degrees and 180 degrees), the system can identify the type of the arbitration line according to the sequence of a plurality of received signal jumping points of the two arbitration lines and the time difference between the signal jumping points, so that the data bus corresponding to the arbitration line is further confirmed.
For example, as shown in fig. 5, 1 in the figure represents a voltage change curve of the arbitration line 1 (horizontal axis represents time and vertical axis represents level), 2 in the figure represents a voltage change curve of the arbitration line 2 (horizontal axis represents time and vertical axis represents level), and clk in the figure represents a clock signal of the present communication node. The preset phase difference of arbitration line 1 is 0, which means that the difference between the transmission time point of each symbol transmitted to arbitration line 1 and the rising edge of the clock cycle is 0; the arbitration line 2 has a preset phase difference of 90 °, which indicates a clock cycle in which the difference between the transmission time point of each symbol transmitted to the arbitration line 2 and the rising edge of the clock cycle is one quarter; one quarter of the clock period indicates a phase difference of 90.
As can be seen from fig. 5, in one clock cycle, the sending time point of the arbitration line 2 is earlier than 1/4T (T is a clock cycle) of the arbitration line 1 by 3/4T (T is a clock cycle) and the next sending time point of the arbitration line 1, and further the ratio of the time difference of the adjacent arbitration line signals is 1:3, and this rule is applied to the receiving end, and the receiving end identifies the arbitration line according to the ratio of the time differences of the signal transition time points of the received multiple consecutive arbitration lines, for example, the ratio is 1:3, and the arbitration line received first is arbitration line 1; if the ratio is 3:1, the arbitration line received first is arbitration line 2.
The embodiment adopts a quasi-synchronous mode based on a system clock, and two arbitration lines are respectively driven according to a fixed phase difference to support blind plugging of a bus connector, so that the system is convenient for users to use. The same scheme is applied to a synchronous system, blind plugging and unplugging of a bus connector can be realized, but the synchronous system is more complex and supports a limited transmission distance in order to realize a synchronous mode.
In another embodiment of the present invention, as shown in fig. 1, a high speed data transmission system includes:
on the basis of the first embodiment, the following steps are added: the high-speed data transmission system adopts an asynchronous mode.
The function of each communication node is replaced by:
each communication node includes:
an arbitration interface module 100, configured to send an identifier composed of a plurality of symbols onto the arbitration line, wherein when consecutive same symbols are sent, the symbols are sent with a different encoding result from a previous symbol.
And a data sending module 300, configured to send its data to the data bus.
The control module 200 is configured to dynamically select an arbitration line according to the idle rates of different arbitration lines when it is detected that the arbitration module has a data transmission requirement, and control the arbitration interface module to transmit an identifier of the arbitration interface module to the arbitration line in a current arbitration frame; and when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and controls the data transmission module to transmit own data to a target data bus in the next data frame.
Specifically, the identifier is composed of a plurality of multilevel symbols, and at least comprises two multilevel symbols. The multilevel symbol is composed of a plurality of threshold separated different voltage amplitudes. The mapping between the multilevel symbols and the different voltages represents a coding scheme. Generally, the system adopts one coding mode, but the embodiment adopts two coding modes, each symbol has different coding results under different coding modes, namely corresponding to different voltages, when continuously same symbols are sent to an arbitration line, the different coding results with the previous symbol are adopted for sending, therefore, even if the same symbols are sent to the arbitration line, the obvious voltage change exists, the end of the previous symbol and the start of a new symbol can be known through the voltage change, and simultaneously, the clock signal is convenient to recover and position. Therefore, the method is beneficial to each communication node in the asynchronous system to accurately identify the end and the start of each symbol during data receiving, thereby further accurately decoding the symbols on the arbitration line.
Because different symbols correspond to different coding results in the same coding mode, when the transmitted symbol is different from the previous symbol, the transmission can continue to adopt the coding result in the same coding mode as the previous symbol.
For example, as shown in table 1, there are 8 levels:
for a twisted pair with a bus voltage fluctuating between 0 and 7V, a definition is that the voltage is 0 when the voltage is lower than 0.5V, 1 when the voltage is between 0.5V and 1.5V, 2 when the voltage is between 1.5V and 2.5V, 3 when the voltage is between 2.5V and 3.5V, 4 when the voltage is between 3.5V and 4.5V, 5 when the voltage is between 4.5V and 5.5V, 6 when the voltage is between 5.5V and 6.5V, and 7 when the voltage is higher than 6.5V.
There are 4 kinds of symbols, and the system has two coding modes, each symbol corresponds to two levels, level 1 and level 2. The identifier consists of 3-bit symbols. When the communication node with the identifier of 000 sends the identifier to the arbitration line, if only one coding method is adopted, the level on the corresponding arbitration line is 000, and the level on the arbitration line is 030 in the manner of this embodiment. If no communication node transmits an identifier (i.e., the arbitration line is idle), the arbitration line defaults to level 0, and it is difficult to distinguish whether no communication node has a data transmission request, whether the communication node has identifier 000, or whether the arbitration line is abnormal, and always remains at level 0, based on level 000.
TABLE 1
The symbol sending rule of the embodiment is beneficial to accurately identifying the end and the start of each symbol when each communication node in the asynchronous system receives data, so that the symbols on the arbitration line are further accurately decoded, and the success rate of decoding is improved; the system is also beneficial to distinguishing the bus fault from the normal code, the fault identification capability of the system is improved, and the anti-interference capability of the system is enhanced.
Although this embodiment is directed to an asynchronous system, the symbol transmission rule is also applicable to a quasi-synchronous system and a synchronous system. Although the end and the start of each symbol can be identified according to the uniform system clock in a synchronous mode, the symbol sending rule is beneficial to a system to distinguish bus faults from normal codes, and the fault identification capability of the system is improved.
In an embodiment of the present invention, as shown in fig. 2, a high speed data transmission method based on the high speed data transmission system described in any of the foregoing embodiments includes:
step S100 selects an arbitration line from the communication nodes having a data transmission requirement in the current arbitration frame, and transmits their own identifiers to the arbitration line.
Specifically, each communication node has a unique identifier for identifying itself, and the identifier is composed of one or more symbols. Each communication node must first send its own identifier on the arbitration line before sending data, and can only send on the data bus after the own identifier is successfully sent on the arbitration line. Since the system has two arbitration lines each controlling one pair of data buses and two pairs of data buses, and different arbitration lines controlling different data buses, each communication node must first select one arbitration line before transmitting data and then transmit its own identifier on that arbitration line. There are various ways to select the arbitration line, one arbitration line can be selected fixedly, or the arbitration line can be selected dynamically each time an identifier is sent; there are many ways to dynamically select the arbitration line, such as random selection, or to optimize the arbitration line with high idleness rate according to the idle condition of the arbitration line to reduce the probability of collision.
Step S200, the communication node detects whether the identifier of the communication node is successfully transmitted.
Specifically, after the communication node sends a symbol of one bit of the identifier, the communication node monitors the symbol on the arbitration line; when the symbol on the arbitration line is different from the symbol transmitted by the communication node, the transmission of the identifier is considered to be failed, and the transmission of the subsequent symbol of the identifier is stopped; when the symbol on the arbitration line is the same as the symbol sent by the communication node, indicating that the communication node successfully sends the one-bit symbol of the identifier; if there are more symbols to send, continuing to send the next symbol of the identifier; when the communication node successfully transmits all symbols of the identifier, the transmission of the identifier is considered successful.
Step S300, when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and transmits its own data to a target data bus in the next data frame, where the target data bus is a data bus controlled by the arbitration frame.
Specifically, when a plurality of communication nodes simultaneously transmit identifiers, the communication nodes capable of correctly transmitting the identifiers to the arbitration line obtain arbitration wining of the current arbitration frame to become a wining communication node, obtain the use right of the next data frame of the target data bus, and simultaneously, the arbitration is finished. The target data bus refers to the data bus controlled by the arbitration line. At the next arbitration frame, all devices again participate in arbitration.
Because two pairs of data buses exist, at most two communication nodes can be contended in each arbitration frame to obtain the use right of the data buses, and therefore the data transmission rate of the system is improved.
In another embodiment of the present invention, as shown in fig. 3, a high speed data transmission method based on the high speed data transmission system described in any of the previous embodiments includes:
the system clock of the high-speed data transmission system adopts a quasi-synchronous mode.
Specifically, the plesiochronous mode is to recover a clock signal and a positioning clock signal through a deviation between preset phase differences used by a bus and to allow the clock signal to serve as a system reference clock. The system is provided with high-precision clock samplers at each communication node, and the error between the signals of the clocks is within the acceptable range of the system. Therefore, although the system has a uniform clock signal, no extra wiring harness is provided for transmitting the clock signal, so that the synchronization mode is not true synchronization strictly, and is called as quasi-synchronization.
The synchronous mode means that the system has a uniform reference clock, and each communication node transmits and receives data based on the uniform reference clock.
Step S110 dynamically selects an arbitration line according to the idle rates of different arbitration lines at the current arbitration frame by the communication node having the data transmission requirement.
Specifically, the idle rate of the arbitration line may be calculated according to the idle times of the arbitration line in a certain time, for example, arbitration line 1, 50 arbitration frames out of 100 consecutive arbitration frames do not have any communication node sending an identifier to the arbitration line, indicating that the idle rate is 50%; arbitration line 2, 10 arbitration frames out of 100 consecutive arbitration frames do not have any communication node sending an identifier onto the arbitration line, indicating that the idle rate is 10%; according to the idle rate, the arbitration line 2 is busy than the arbitration line 1, when a certain communication node has a data transmission demand, the arbitration line with high idle rate is preferentially selected, namely the arbitration line 1 is selected, the probability of collision is low, and the use right of the data bus can be more easily obtained.
Step S120 sends its own identifier onto the arbitration lines according to a preset phase difference, wherein the deviation between the preset phase differences of the two arbitration lines is located at (0 °,180 °).
Specifically, the preset phase difference of the arbitration line refers to a phase difference of a transmission time point of the communication node from a clock signal (for example, a rising edge of one clock cycle) of the communication node when transmitting each symbol of the identifier to the arbitration line. The transmission time point at which the identifier is transmitted to the corresponding arbitration line can be determined based on the preset phase difference and the clock signal of the present communication node.
Each communication node of the system is connected to a system bus by a bus connector that includes two pairs of data buses and two arbitration lines. When the signal lines included in the bus connector are symmetrically arranged (for example, the data bus 1 arbitration line 2 data bus 2), the bus connector is easy to be inserted reversely in operation, and is similar to the data line of an apple mobile phone, so that the system is required to support the insertion and extraction of the bus connector in any direction, otherwise, the wrong insertion is required to be avoided through the structure of the bus connector.
When the two arbitration lines are provided with different preset phase differences and the deviation between the preset phase differences of the two arbitration lines is between (0 degrees and 180 degrees), the system can identify the type of the arbitration line according to the sequence of a plurality of received signal jumping points of the two arbitration lines and the time difference between the signal jumping points, so that the data bus corresponding to the arbitration line is further confirmed. Preferably, the deviation is 135 °, or 120 °.
For example, as shown in fig. 5, 1 in the figure represents a voltage change curve of the arbitration line 1 (horizontal axis represents time and vertical axis represents level), 2 in the figure represents a voltage change curve of the arbitration line 2 (horizontal axis represents time and vertical axis represents level), and clk in the figure represents a clock signal of the present communication node. The preset phase difference of arbitration line 1 is 0, which means that the difference between the transmission time point of each symbol transmitted to arbitration line 1 and the rising edge of the clock cycle is 0; the arbitration line 2 has a preset phase difference of 90 °, which indicates a clock cycle in which the difference between the transmission time point of each symbol transmitted to the arbitration line 2 and the rising edge of the clock cycle is one quarter; one quarter of the clock period indicates a phase difference of 90.
As can be seen from fig. 5, in one clock cycle, the sending time point of the arbitration line 2 is earlier than 1/4T (T is a clock cycle) of the arbitration line 1 by 3/4T (T is a clock cycle) and the next sending time point of the arbitration line 1, and further the ratio of the time difference of the adjacent arbitration line signals is 1:3, and this rule is applied to the receiving end, and the receiving end identifies the arbitration line according to the ratio of the time differences of the signal transition time points of the received multiple consecutive arbitration lines, for example, the ratio is 1:3, and the arbitration line received first is arbitration line 1; if the ratio is 3:1, the arbitration line received first is arbitration line 2.
Step S200, the communication node detects whether the identifier of the communication node is successfully transmitted.
Step S300, when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and transmits its own data to the target data bus in the next data frame. The target data bus is a data bus controlled by the arbitration frame.
The embodiment adopts a quasi-synchronous mode based on a system clock, not only can save system wiring harness resources, but also can support blind plugging of a bus connector by symmetrically arranging an arbitration bus and a data bus, and is convenient for a user to use. The same scheme is applied to a synchronous system, blind plugging and unplugging of a bus connector can be realized, and the complexity of the system can be increased for realizing the synchronous mode of the synchronous system.
In another embodiment of the present invention, as shown in fig. 4, a high speed data transmission method includes:
the high-speed data transmission system adopts an asynchronous mode.
Step S110 dynamically selects an arbitration line according to the idle rates of different arbitration lines at the current arbitration frame by the communication node having the data transmission requirement.
Step S130 transmits an identifier composed of a plurality of symbols onto the arbitration line, wherein when consecutive identical symbols are transmitted, the transmission is performed with a different encoding result from the previous symbol.
Specifically, the identifier is composed of a plurality of symbols, and at least comprises two symbols. Each symbol is encoded and converted to a voltage and sent to the arbitration line. The mapping between symbols and voltages represents one way of encoding. Generally, the system adopts one coding mode, but the embodiment adopts two coding modes, each symbol has different coding results under different coding modes, namely corresponding to different voltages, when continuously same symbols are sent to an arbitration line, the coding results are sent by adopting different coding results from the previous symbol, so that even if the same symbols are sent to the arbitration line, the voltage change is obvious, the end of the previous symbol and the start of a new symbol can be known through the voltage change, therefore, the method is favorable for each communication node in the asynchronous system to accurately identify the end and the start of each symbol during data receiving, and further accurately decode the symbols on the arbitration line.
Because different symbols correspond to different coding results in the same coding mode, when the transmitted symbol is different from the previous symbol, the transmission can continue to adopt the coding result in the same coding mode as the previous symbol.
For example, as shown in table 2, there are 8 levels:
for a twisted pair with a bus voltage fluctuating between 0 and 7V, a definition is that the voltage is 0 when the voltage is lower than 0.5V, 1 when the voltage is between 0.5V and 1.5V, 2 when the voltage is between 1.5V and 2.5V, 3 when the voltage is between 2.5V and 3.5V, 4 when the voltage is between 3.5V and 4.5V, 5 when the voltage is between 4.5V and 5.5V, 6 when the voltage is between 5.5V and 6.5V, and 7 when the voltage is higher than 6.5V.
There are 4 kinds of symbols, and the system has two coding modes, each symbol corresponds to two levels, level 1 and level 2. The identifier consists of 3-bit symbols. When the communication node with the identifier of 000 sends the identifier to the arbitration line, if only one coding method is adopted, the level on the corresponding arbitration line is 000, and the level on the arbitration line is 030 in the manner of this embodiment. If no communication node transmits an identifier (i.e., the arbitration line is idle), the arbitration line defaults to level 0, and it is difficult to distinguish whether no communication node has a data transmission request, whether the communication node has identifier 000, or whether the arbitration line is abnormal, and always remains at level 0, based on level 000.
TABLE 2
| |
|
||
| | Level | 1 | |
| 0 | 0 | 3 | |
| 1 | 2 | 5 | |
| 2 | 4 | 7 | |
| 3 | 6 | 1 |
Step S200, the communication node detects whether the identifier of the communication node is successfully transmitted.
Step S300, when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and transmits its own data to the target data bus in the next data frame. The target data bus is a data bus controlled by the arbitration frame.
The symbol sending rule of the embodiment is beneficial to accurately identifying the end and the start of each symbol when each communication node in the asynchronous system receives data, so that the symbols on the arbitration line are further accurately decoded, and the success rate of decoding is improved; the system is also beneficial to distinguishing the bus fault from the normal code, the fault identification capability of the system is improved, and the anti-interference capability of the system is enhanced.
Although this embodiment is directed to an asynchronous system, the symbol transmission rule is also applicable to a quasi-synchronous system and a synchronous system. Although the end and the start of each symbol can be identified according to the uniform system clock in a synchronous mode, the symbol sending rule is beneficial to a system to distinguish bus faults from normal codes, and the fault identification capability of the system is improved.
It should be noted that the above embodiments can be freely combined as necessary. The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A high speed data transmission system, comprising:
the data bus is transmitted by taking a data frame as a unit;
the arbitration device comprises two arbitration lines and a control unit, wherein the two arbitration lines are respectively used for controlling the election function of data sending rights of different data buses, each arbitration line takes an arbitration frame as a unit to transmit, the transmission time of the arbitration frame is the same as that of the data frame, and each arbitration frame is used for transmitting an identifier of a winner communication node;
the communication nodes are respectively connected in parallel and hung on the data buses and the arbitration line;
each communication node includes:
the arbitration interface module is used for sending the identifier of the arbitration interface module to an arbitration line;
the data sending module is used for sending own data to the data bus;
the control module is used for selecting an arbitration line when detecting that the arbitration interface module has a data transmission requirement, and controlling the arbitration interface module to transmit an identifier of the arbitration interface module to the arbitration line in a current arbitration frame; and when detecting that the identifier is successfully transmitted, the communication node is the dominant communication node of the current arbitration frame, and controls the data transmission module to transmit own data to a target data bus in the next data frame.
2. A high speed data transmission system according to claim 1, characterized in that:
the system clock adopts a quasi-synchronous mode.
3. A high speed data transmission system according to claim 2, characterized in that:
the arbitration interface module is further configured to send its identifier to the arbitration lines according to a preset phase difference, wherein a deviation between the preset phase differences of the two arbitration lines is (0 °,180 °).
4. A high speed data transmission system according to claim 1, characterized in that:
and the control module is further used for dynamically selecting one arbitration line according to the idle rate of different arbitration lines when detecting that the control module has a data transmission demand.
5. A high speed data transmission system according to claim 1, characterized in that:
the arbitration interface module is further configured to send an identifier composed of a plurality of symbols to the arbitration bus, where when consecutive same symbols are sent, the identifier is sent using a different encoding result from a previous symbol.
6. A high-speed data transmission method applied to the high-speed data transmission system according to claim 1, comprising:
in the current arbitration frame, a communication node with a data transmission requirement selects an arbitration line and transmits an identifier of the communication node to the arbitration line;
and when the identifier is detected to be successfully sent, the communication node is a winning communication node of the current arbitration frame, and sends own data to a target data bus in the next data frame, wherein the target data bus is a data bus controlled by the arbitration frame.
7. The high-speed data transmission method according to claim 6, further comprising:
the system clock adopts a quasi-synchronous mode.
8. The method of claim 7, wherein sending the own identifier onto the arbitration line comprises:
the own identifier is sent to the arbitration lines with a predetermined phase difference, wherein the deviation between the predetermined phase differences of the two arbitration lines is located at (0 °,180 °).
9. The method of claim 6, wherein the communication node having a data transmission requirement selects an arbitration line comprising:
the communication node with the data transmission requirement dynamically selects one arbitration line according to the idle rate of different arbitration lines.
10. The method of claim 6, wherein sending the own identifier onto the arbitration line further comprises:
an identifier consisting of a plurality of symbols is sent onto the arbitration line, wherein when consecutive identical symbols are sent, the transmission is performed with a different encoding result from the previous symbol.
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