| In modern electronic equipment,the types of electrical signals are becoming more and more abundant.The communication protocols used between devices are also more complicated.As a mainstream electrical signal debugging tool,ordinary digital oscilloscopes have been unable to meet the requirements of users to analyze complex protocol signals.However,the domestic high-end oscilloscopes with protocol analysis functions mainly support simple and common protocols such as I~2C,SPI,and USB,and there are fewer types of protocols supported.Therefore,thesis designs a protocol analysis and decoding function for the complex protocols MDIO,CAN FD and PCIe1.0,and conducts the following research on the three aspects of signal analysis,triggering and decoding data transmission in this function:1.In the analysis of the protocol signal,in order to obtain and analyze the information carried in the protocol signal,according to the transmission characteristics of the three protocol signals,different processing methods are adopted.MDIO protocol recovers the data information with the help of the accompanying clock signal line.CAN FD protocol data line embeds the clock signal,with bit-stuffing encoding method.By generating clock pulses,the padding bits in the bit-stuffing encoding are filtered and processed to restore its real information;PCIe1.0 protocol has scrambling code and8b/10b encoding,as well as the characteristics of fast signal transmission speed and large amount of data carried.Therefore,a parallel data processing method is designed to match the amount of data transmitted by PCIe 1.0 by shifting the sampling point,and then the data information is restored by 8b/10b decoding and parallel data descrambling.2.In terms of protocol signal triggering,in order to facilitate users to capture the signals of interest more quickly,8,15,and 18 trigger modes are provided for MDIO,CAN FD,and PCIe1.0 protocols,including start-stop status,signal flags and data information and other conventional triggers,as well as error detection triggers such as coding errors,CRC errors,and packet format errors.The design difficulty lies in the variety of triggers,and in order to meet the needs of high-speed signal calculation and improve data processing speed,design a parallel CRC calculation method for PCIe1.0 protocol CRC error checking.3.In terms of protocol decoding data transmission,in order to visualize the information carried by the protocol signal,a decoding data packet is designed to encapsulate the valid characters and data information carried in the protocol signal,and then cache it in hardware and upload it to the industrial computer.After the software system parses the data packet,it is displayed in the form of a decoding label to achieve the decoding function.Thesis designs the analysis and decoding functions of three serial protocol signals in the digital oscilloscope.The experimental verification shows that it can analyze the MDIO protocol with the highest 2.5 Mbps,the CAN FD protocol with the fastest 8 Mbps,and the PCIe1.0 protocol.The trigger positioning of the signal is accurate,and the character information and data information displayed on the decoding label are consistent with the signal waveform,which meets the requirements of the design index and verifies the effectiveness of the function.Signal debuggers can use this function to effectively test and analyze serial protocol signals,which realized the diversity of instrument functions,and improved the practical value of the instrument. |
