EEPROM, EEPROM
In the early days of the development of the microcomputer, the BIOS was stored in a ROM (Read Only Memory). The internal data of the ROM is burned in a special way in the manufacturing process of the ROM. The contents of the ROM can only be read and cannot be changed. Once it is burned in, the user can only verify whether the written data is correct. No further modifications can be made. If you find any errors in the data, you can only make a copy if you don't use it. ROM is produced on the production line and is generally used only in high-volume applications due to its high cost.
Due to the inconvenience of ROM manufacturing and upgrading, a PROM (Programmable ROM) was later invented. Initially, there is no data inside the PROM made in the factory. The user can write his own data with a dedicated programmer, but this opportunity is only once. Once it is written, it cannot be modified. If an error occurs, it is written. The chip can only be scrapped. The characteristics of the PROM are the same as those of the ROM, but the cost is higher than that of the ROM, and the speed of writing data is slower than that of the ROM. Generally, it is only suitable for a small number of occasions or for pre-production verification of the ROM.
The EPROM (Erasable Programmable ROM) chip can be repeatedly erased and written, which solves the drawback that the PROM chip can only be written once. The EPROM chip has a very obvious feature. On the ceramic package on the front side, a glass window is opened through which the integrated circuit can be seen. The ultraviolet light can be erased through the hole to illuminate the internal chip. The internal data, the EPROM eraser is used to complete the chip erase operation. The writing of the data in the EPROM requires a dedicated programmer, and a certain programming voltage must be added when writing content to the chip (VPP=12-24V, depending on the chip model). The EPROM model starts with 27, such as 27C020 (8*256K) is a 2M Bits capacity EPROM chip. After writing the data, the EPROM chip also seals the window with an opaque sticker or tape to protect the data from the surrounding ultraviolet rays.
Fundamental:
Due to the inconvenience of EPROM operation, most of the BIOS ROM chips on the motherboard are EEPROM (Electrically Erasable Programmable ROM). EPROM erase does not need to rely on other equipment, it is to modify its contents with electronic signals, and Byte is the minimum modification unit, you do not have to wash all the data to write, completely get rid of EPROM Eraser and programmer Bondage. When EPROM writes data, it still needs to use a certain programming voltage. At this time, it is easy to rewrite the content with a dedicated refresh program provided by the manufacturer. Therefore, it belongs to a dual voltage chip. By means of the dual voltage characteristic of the EPROM chip, the BIOS can have a good anti-virus function. When upgrading, the jumper switch is turned to the "ON" position, that is, the corresponding programming voltage is added to the chip, and the upgrade can be conveniently performed; When used normally, the jumper switch is turned to the "OFF" position to prevent illegal modification of the BIOS chip by the CIH virus. Therefore, many motherboards still use EPROM as a BIOS chip and have become a major feature of their motherboards.
The main function of the safety barrier is to restrict the dangerous energy in the safe place from entering the dangerous place, that is, to limit the voltage and current sent to the dangerous place.
1. Due to the tripartite isolation mode, there is no need for system grounding line, which brings great convenience to the design and on-site construction. The requirements for instruments in hazardous areas are greatly reduced, and isolated instruments are not required on site.
2. Since the signal line does not need to be grounded together, the stability and anti-interference ability of the detection and control circuit signal are greatly enhanced, so as to improve the reliability of the whole system.
3. The isolated safety barrier has stronger input signal processing ability and can accept and process thermocouple, thermal resistance, frequency and other signals, which is impossible for Zener safety barrier.
4. The isolated safety barrier [2] can output two mutually isolated signals to be used by two equipment using the same signal source, ensure that the signals of the two equipment do not interfere with each other, and improve the electrical safety insulation performance between the connected equipment.
Isolated Safety Barrier,Output Intrinsic Isolated Safety Barrier,Explosion-Proof Relay Isolated Barrier,Switch Explosion-Proof Relay Barrier
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