Design and Application of EEPROM Based on Serial Communication in TV
1 Introduction
In recent years, digital TV technology has developed rapidly, especially the introduction of remote control systems. Various manufacturers have added microprocessors (MCUs) to TV sets. Various artificial intelligence color TVs have completely replaced the manual (mechanical) control and memory of old TVs. the way. With the increasingly powerful functions of TV-specific MCUs, the functions used by users are becoming more and more abundant, the data required to be stored and the refresh speed are continuously improved, and various models and specifications of memory have emerged successively. At present, the most widely used TV set is E2PROM.
Because E2PROM holds a large amount of data closely related to the working state of the TV, its reliability is crucial to remote control TV and is regarded as the second core device. The E2PROM maintains communication with the first core device (MCU) and stores the working information of the TV. Sometimes, due to the loss of stored data, significant losses are caused, and even the data cannot be repaired. Therefore, in the television system, for the storage of system data and user data generally use electrically erasable memory E2PROM. E2PROM has the advantages of easy operation, long data storage time, wide storage temperature range, and many erasable times. The serial communication E2PROM represented by the AT24CXX series introduced by ATMEL has gradually become the first choice for E2PROM in TV product design due to its advantages of reliable quality and simple interface.
2 Introduction to AT24CXX series
Compared with parallel communication memory, serial communication memory is widely used due to its advantages of occupying few resources, I / O bus, and small size. Typical serial communication E2PROM AT24CXX is an I2C bus serial device, with a wide operating power supply (1.8 ~ 5.5 V), strong anti-interference ability f input pin built-in Schmitt trigger filter to suppress noise), low power consumption (write state The maximum working current is 3 mA), high reliability (1 million write times, data storage for 100 years), support online programming and other features.
Figure 1 AT24CXX internal structure diagram
Figure 1 shows the block diagram of the internal structure of AT24CXX. The SDA pin can realize bidirectional serial data transmission. The rising edge of the clock signal input at the SCL pin sends data into the E2PROM, and the data is read out at the falling edge of the clock.
According to the size of the memory space address, AT24CXX is divided into C02 / 2K, C04 / 4K, C08 (A) / 8K, C16 / 16K and other versions. In addition to the different storage space, the internal performance of each version of the device is basically the same, users can Choose the appropriate device according to the actual conditions of use. The A2, A1, and A0 pins are the device address input pins of the AT24CXX hardware connection. Up to 8 AT24C02 or 4 AT24C04 or 2 AT24C08 (A) or 1 AT24C16 can be connected to one bus.
In addition, AT24CXX series devices have pins for hardware data write protection. When this pin is connected to a low level, the device is allowed to read / write normally; when this pin is connected to a high level, the device starts the write protection function. Table 1 shows the description of the write protection function and storage structure of each version of the device.
3 AT24CXX design and application in color TV
Although the number of peripheral pins and components of AT24CXX is very small, and the interface circuit is simple, in actual CRT color TV applications, due to interference signals such as high-voltage flashover in the TV, E2PROM will have some "strange" phenomena, resulting in abnormal TV operation. The main phenomena that cause the TV to work abnormally are given below.
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