In order to establish a safe and effective road operating environment, car tachographs have been used more and more widely as an effective monitoring tool. The car tachograph needs to quickly record and store the key information of the vehicle every 0.2s, and Fujitsu FeRAM Memory has the characteristics of fast write cycle without waiting, almost unlimited number of erasing and writing, and non-volatile characteristics. It provides a stable and reliable memory solution for the storage of key information after an automobile accident.
With the rapid development of the economy, the number of cars has also increased by leaps and bounds; at the same time, the problems of traffic safety and traffic congestion are becoming more and more serious. Statistical analysis proves that a considerable part of the traffic accidents are caused by the driver’s fatigue driving and other illegal driving behaviors. Therefore, in order to manage road transport vehicles more effectively and provide everyone with a safe road operating environment, the relevant government departments of the state have decided to make it mandatory for all operating vehicles to install car driving recorders from September 2012 (operating vehicles include: all school buses, Highway passenger cars and tourist buses, buses without passenger standing areas, dangerous goods transport vehicles, semi-trailer tractors and trucks with a total mass greater than or equal to 12000kg), and the national standard GB/T 19056-2012 has been issued to define the vehicle driving recorder. Function, shape, interface standard and other indicators.
Car driving recorder, also known as “car black box”, records and stores the driving speed, time, mileage, position, brake and other information about the driving of the vehicle and the condition of the vehicle itself, and can realize data output through data communication digital electronic recording device. It must have data storage function, communication function, printing function and display function (as shown in the figure below).
This article will discuss the memory requirements and options for data storage functions.
The data storage function can be divided into two parts: real-time data storage and historical data storage. Car real-time data is mainly used to analyze the cause of the accident and the responsibility of the accident. The historical data of the car provides a reference basis for accident analysis or provides the basis for the assessment of the operating conditions of the car and the driver. Whether it is real-time data or historical data of the car’s driving, it must include these information: speed, brakes, turn signals, location information, date, etc.
The storage requirements for historical data are not high, as long as the data is stored in the specified memory at a specified long time interval (such as every hour), so the selection of this type of memory is also relatively easy. At present, large-capacity FLASH, SD card or Hard disk, U disk can meet the requirements. For the storage of real-time data, this requirement is relatively strict, because the real-time data will be updated in 0.2S (the national standard requires that 20s-long accident suspect data be collected every 0.2s, and it is required to continuously save nearly 100 pieces of data) and the equipment is required to be disconnected. After the power is turned on, the driving information and location information can be saved for 20s. Therefore, the selection of real-time memory must meet the following requirements:
1) Fast write operation;
The data storage function can be divided into two parts: real-time data storage and historical data storage. Car real-time data is mainly used to analyze the cause of the accident and the responsibility of the accident. The historical data of the car provides a reference basis for accident analysis or provides the basis for the assessment of the operating conditions of the car and the driver. Whether it is real-time data or historical data of the car’s driving, it must include these information: speed, brakes, turn signals, location information, date, etc.
The storage requirements for historical data are not high, as long as the data is stored in the specified memory at a specified long time interval (such as every hour), so the selection of this type of memory is also relatively easy. At present, large-capacity FLASH, SD card or Hard disk, U disk can meet the requirements. For the storage of real-time data, this requirement is relatively strict, because the real-time data will be updated in 0.2S (the national standard requires that 20s-long accident suspect data be collected every 0.2s, and it is required to continuously save nearly 100 pieces of data) and the equipment is required to be disconnected. After the power is turned on, the driving information and location information can be saved for 20s. Therefore, the selection of real-time memory must meet the following requirements:
1) Fast write operation;
2) Unlimited write cycles;
3) Data will not be lost after power failure;
4) High reliability;
It can be seen that only ferroelectric memory (FRAM) can meet the requirements of real-time data storage of automobile driving. The following figure is a functional block diagram of a tachograph based on ferroelectric memory (FRAM):In summary, according to the description of the real-time data memory requirements of the car tachograph, the ferroelectric memory (FRAM) with SPI or I2C interface, such as MB85RS64, MB85RS256 or MB85RC64TA, can meet the design requirements.
