The relationship between FLASH and RAM, ROM

The single-chip FLASH is mainly used as a program memory, which is to replace the previous ROM. The biggest one is to reduce the cost of the chip and can be electrically erased. Currently, the FALSH life of the single-chip microcomputer on the market is quite different, and the number of erasing and writing is from 1000. ~100,000 are available, but the storage time can be guaranteed for 40 years, pay attention to when choosing. There are also some inexpensive MCUs that do not use expensive EEPROMs to integrate the power-down data memory, but use FALSH to do it, but pay attention to its lifetime of up to 100,000 times, and erasing can not be byte-written, this Pay attention to the occasions where the life is satisfactory.

RAM is a data memory, similar to the memory inside the computer. It is mainly used to store the process data in the running of the program. After the power is turned off, the previous data will be lost. Therefore, the program needs to be initialized when it is powered on, otherwise the data after power-on. Is a random number that can cause a program to crash.

ROM is the program memory, the data will not be lost after power-off, but its data will not change during the running of the program. The ROM of the early MCU has been replaced by the current FLASH memory because of the trouble of erasing the modification, the expensive or low-cost OTP type cannot modify the data. Because FLASH is easy to erase, some of the current MCUs support online internal programming. The specific program execution mode can modify the content of FALSH, and realize the online modification of program memory. This does not conflict with the content of the program memory mentioned above when it is running, because the content does not change when the program is running normally, and only works in the read-only state.

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