CN106851854B - Serial communication frame structure and multi-node random access method - Google Patents
Serial communication frame structure and multi-node random access method Download PDFInfo
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Abstract
A serial communication frame structure and a multi-node random access method are provided, wherein the serial communication frame structure is provided with the following components in sequence: a 16-bit header, a 600ns guard interval, an 8-bit sync field, a 2048-bit data field, a 16-bit CRC check field, and an 800ns guard interval. The method comprises the following steps: continuously receiving serial communication data when a node starts to access, clearing a first counter, and starting to search a protection gap larger than 600ns in a serial communication frame node; carrying out baud rate judgment on the 16-bit frame header from the received first high-level bit, and counting the number of the received bits by the second counter; if the baud rate is 5Mbps and the count of the second counter is 16, judging whether the protection gap is greater than 400ns, if so, when the received serial communication data is a high-low conversion sequence of 10101010; judging whether the data field is finished according to the data length information; and the frame synchronization is successful, namely the node is successfully accessed. The invention ensures the reliability and the availability of the bus to be greatly ensured.
Description
Technical Field
The present invention relates to a communication system. In particular, to a serial communication frame structure and a multi-node random access method.
Background
In many industrial field applications, an apparatus is usually composed of a plurality of nodes, each node has independent function but needs to communicate with each other, so that an interconnection method is needed for achieving the purpose of mutual communication. In order to improve the reliability of interconnection and reduce the cost of interconnection, in the case that the communication bandwidth requirement is not very high, the interconnection is often performed by means of serial communication as shown in fig. 1.
Under the harsh requirement, the equipment can require single data channel to be interconnected without a clock, and interconnection resources are greatly saved. Meanwhile, in order to improve the availability of the system, all nodes are required to be randomly accessed to the system. In this case, it is very important to design a good serial frame structure and random access method for system availability.
The serial frame structure not only needs to reasonably arrange the communication structure of data, but also needs to consider the recovery of data without a synchronous clock and the protection gap between frames.
As shown in fig. 2, a complete frame mainly comprises a frame header, a synchronization field, a data field, and a CRC check field. There is a 800ns guard gap from frame to frame and a 600ns guard gap between the header and sync fields.
The frames are in a variable rate manner for the need of multiple nodes to compete for the bus. The frame header 16bit adopts a baud rate of 5Mbps, and other fields all adopt a baud rate of 50Mbps with a higher rate.
There are two random cases for all nodes in the system: firstly, all nodes can randomly access or withdraw from the system, which can cause the topology of the system composition to change; second, all nodes can randomly transmit the data they want to transmit.
When a node randomly withdraws, an incomplete frame of an outgoing line on the bus can be caused, and if the system node cannot judge the error frame or the incomplete frame, the system bus is hung up and cannot continue to work.
When a node randomly accesses and immediately sends, an error occurs in a frame being transmitted on the bus, so that the system bus is hung up.
Therefore, in order to solve the above problem, it is necessary to correctly parse the frame currently transmitted through the bus, clearly identify the field in which the current bus transmission frame is located, correctly find the beginning of the frame, and start accessing.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a serial communication frame structure and a multi-node random access method.
The technical scheme adopted by the invention is as follows: a serial communication frame structure comprises the following components in sequence: a 16-bit header, a 600ns guard interval, an 8-bit sync field, a 2048-bit data field, a 16-bit CRC check field, and an 800ns guard interval.
The 16-bit frame header adopts a baud rate of 5Mbps, and the 8-bit synchronization field, the 2048-bit data field and the 16-bit CRC check field all adopt a baud rate of 50 Mbps.
The first bit of the 16-bit frame header is 1.
The 8-bit synchronization field is a high-low transformation sequence of 10101010.
A multi-node random access method based on a serial communication frame structure comprises the following steps:
1) continuously receiving serial communication data when a node starts to access, simultaneously resetting a first counter, starting to search a protection gap larger than 600ns in a serial communication frame node, entering the next step if the protection gap is found, and otherwise, searching all the time;
2) carrying out baud rate judgment on the 16-bit frame header from the received first high-level bit, and counting the number of the received bits by the second counter; if the baud rate is 5Mbps and the count of the second counter is 16, entering the next step, otherwise, returning to the step 1);
3) judging whether the protection gap is larger than 400ns, if so, entering the next step, and otherwise, returning to the step 1);
4) when the received serial communication data is a high-low transformation sequence of 10101010, entering the next step, otherwise, returning to the step 1);
5) judging whether the data field is finished according to the data length information, judging whether the 16-bit CRC check field is correct when the data field is finished, if so, entering the next step, simultaneously adding 1 to the first counter, and if the 16-bit CRC check field is wrong, returning to the step 1);
6) and the frame synchronization is successful, namely the node is successfully accessed.
And 5) judging whether the data field is finished or not according to the data length information, if so, judging whether the data length information is 2048 bits, if not, finishing, and if not, continuing to judge.
The invention relates to a serial communication frame structure and a multi-node random access method, wherein a frame structure with variable speed is adopted, a frame header with low speed is beneficial to the realization of the random access of nodes, namely bus competition, and once the bus competition is successful, high-speed data transmission is adopted to improve the transmission efficiency of a bus. When the node is accessed, a method of sequentially judging different fields of a frame structure from a time domain is adopted, so that the condition that the bus is hung up due to error frames and incomplete frames is avoided. The reliability and the availability of the bus are greatly ensured.
Drawings
FIG. 1 is a schematic diagram of a system interconnection topology in a serial communication manner;
FIG. 2 is a schematic diagram of a node random access process state machine employing the method of the present invention;
fig. 3 is a schematic diagram of a composition structure of a serial frame.
Detailed Description
A serial communication frame structure and a multi-node random access method thereof according to the present invention will be described in detail with reference to the following embodiments and accompanying drawings.
As shown in fig. 3, a serial communication frame structure of the present invention includes the following components: a 16-bit header, a 600ns guard interval, an 8-bit sync field, a 2048-bit data field, a 16-bit CRC check field, and an 800ns guard interval. That is, there is a 800ns guard gap from frame to frame, and a 600ns guard gap between the header and the sync field. In this case, the frame is in a variable rate mode for the purpose of competing the bus by a plurality of nodes. The 16-bit frame header adopts a baud rate of 5Mbps, and the 8-bit synchronization field, the 2048-bit data field and the 16-bit CRC check field all adopt a baud rate of 50 Mbps; the first bit of the 16-bit frame header is 1; the 8-bit synchronization field is a high-low transformation sequence of 10101010.
As shown in fig. 2, the multi-node random access method based on the serial communication frame structure of the present invention includes the following steps:
1) continuously receiving serial communication data when a node starts to access, simultaneously resetting a first counter, starting to search a protection gap larger than 600ns in a serial communication frame node, entering the next step if the protection gap is found, and otherwise, searching all the time;
2) because the first bit of the frame header is high level, the baud rate of the 16-bit frame header is judged from the first bit of the 16-bit frame header, and meanwhile, the second counter counts the number of received bits; if the baud rate is 5Mbps and the count of the second counter is 16, entering the next step, otherwise, returning to the step 1);
3) judging whether the protection gap is larger than 400ns, if so, entering the next step, and otherwise, returning to the step 1);
4) since the sync field is a 10101010 high-low transform sequence, it can be determined whether the sync field is present. When the received serial communication data is a high-low transformation sequence of 10101010, entering the next step, otherwise, returning to the step 1);
5) because the frame structure has information of data length, whether the data field is finished or not can be judged according to the length information. Judging whether the data field is finished according to the data length information, judging whether the 16-bit CRC check field is correct when the data field is finished, if so, entering the next step, simultaneously adding 1 to the first counter, and if the 16-bit CRC check field is wrong, returning to the step 1); judging whether the data field is finished or not according to the data length information, if so, judging whether the data length information is 2048 bits or not, if not, finishing, and if not, continuing to judge;
6) and the frame synchronization is successful, namely the node is successfully accessed.
Claims (2)
1. A multi-node random access method based on a serial communication frame structure is disclosed, wherein the serial communication frame structure comprises the following components in sequence: 16-bit frame header, 600ns protection gap, 8-bit synchronization field, 2048-bit data field, 16-bit CRC check field and 800ns protection gap; the method is characterized by comprising the following steps:
1) continuously receiving serial communication data when a node starts to access, simultaneously resetting a first counter, starting to search a protection gap larger than 600ns in a serial communication frame node, entering the next step if the protection gap is found, and otherwise, searching all the time;
2) carrying out baud rate judgment on the 16-bit frame header from the received first high-level bit, and counting the number of the received bits by the second counter; if the baud rate is 5Mbps and the count of the second counter is 16, entering the next step, otherwise, returning to the step 1);
3) judging whether the protection gap is larger than 400ns, if so, entering the next step, and otherwise, returning to the step 1);
4) when the received serial communication data is a high-low transformation sequence of 10101010, entering the next step, otherwise, returning to the step 1);
5) judging whether the data field is finished according to the data length information, judging whether the 16-bit CRC check field is correct when the data field is finished, if so, entering the next step, simultaneously adding 1 to the first counter, and if the 16-bit CRC check field is wrong, returning to the step 1);
6) and the frame synchronization is successful, namely the node is successfully accessed.
2. The method according to claim 1, wherein said step 5) of determining whether the data field is ended according to the data length information is to determine whether the data length information is 2048 bits, if so, ending, otherwise, continuing the determination.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1855767A (en) * | 2005-04-18 | 2006-11-01 | 大唐移动通信设备有限公司 | Method for establishing cells with large radius in CDMA communication system synchronized by time division synchronizing codes |
| CN101159483A (en) * | 2007-10-28 | 2008-04-09 | 中兴通讯股份有限公司 | TDD system signal transmission method and the adoptive frame structure thereof |
| CN105554870A (en) * | 2015-12-21 | 2016-05-04 | 海能达通信股份有限公司 | Uplink synchronization method and mobile terminal |
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| US9648616B2 (en) * | 2015-01-15 | 2017-05-09 | Nokia Solutions And Networks Oy | Method and apparatus for implementing efficient low-latency uplink access |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1855767A (en) * | 2005-04-18 | 2006-11-01 | 大唐移动通信设备有限公司 | Method for establishing cells with large radius in CDMA communication system synchronized by time division synchronizing codes |
| CN101159483A (en) * | 2007-10-28 | 2008-04-09 | 中兴通讯股份有限公司 | TDD system signal transmission method and the adoptive frame structure thereof |
| CN105554870A (en) * | 2015-12-21 | 2016-05-04 | 海能达通信股份有限公司 | Uplink synchronization method and mobile terminal |
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