What is the difference between ROM and Ram?

Computer memory is divided into primary memory and secondary memory. The primary memory is also called internal memory (referred to as memory), and the secondary memory is also called external memory (referred to as external memory ). External Storage is usually magnetic media or optical disks, such as hard disks, floppy disks, tapes, and CD. It can store information for a long time and does not rely on electricity to store information.Mechanical PartsDrive, the speed is much slower than the CPU.

Rom and RAM are two types of memory in the computer. Rom indicates read-only memory, that is, it can only read information and cannot write information. After the computer is powered off, its information is still saved, it is generally used to store fixed system software and font libraries. Ram indicates read/write memory. You can perform read or write operations on any of the storage units. After the computer is powered off, its information will not be saved. You need to reload the data when the computer is powered on again, it is usually used to store operating systems, various running software, input and output data, intermediate results, and information exchange with external storage. We often say that memory mainly refers to ram.

Ram (Random Access Memory) ram-Random Access Memory random memory. The content of a storage unit can be retrieved or stored as needed, and the access speed is irrelevant to the location of the storage unit. This type of storage will lose its storage content when the power is down, so it is mainly used to store programs that are used for a short time. Random memory is dividedStatic random memory (static RAM, SRAM) and dynamic random memory (Dynamic RAM, Dram ). The so-called "Random Access" means that when a message in the memory is read or written, the time required is irrelevant to the location of the message.Sequential access (sequential
Access) When storing information in a device, the required time and location are related (such as tape ).

Features: 1. Random Access 2. Volatility 3. High access speed 4. Need to be refreshed 5. Sensitive to Static Electricity

SRAM is short for static RAM. It is a kind of memory with static access function. It can save the data stored inside it without refresh the circuit, while DRAM (Dynamic RAM) refresh and refresh each time, otherwise the internal data will disappear. Therefore, SRAM has high performance, but it also has its disadvantages, that is, it has a low degree of integration, DRAM Memory of the same capacity can be designed as a smaller volume, but SRAM requires a large volume and consumes a large amount of power. Therefore, the SRAM memory on the motherboard occupies part of the area. SRAM is mainly used for second-level high-speed cache.

Note:: There is another SDRAM, which is only one type of DRAM and is the mainstream memory. It is short for synchronous dynamic random access memory, that is, synchronous dynamic random memory. Synchronization means that memory needs to synchronize the clock, and internal command sending and data transmission are based on it; dynamic means that the storage array needs to be constantly refreshed to ensure data is not lost; random means that the exponential data is not stored in a linear order, but the data is read and written at the specified address freely.

MCU flashIt is mainly used as a program storage device to replace the previous Rom. The biggest advantage is that it reduces the cost of the chip and can be wiped by electricity. At present, the falsh life of Single Chip Microcomputer on the market is quite different, the number of erase writes ranges from 1000 ~ 0.1 million, but the storage period can be 40 years. The ROM of early single-chip microcomputer has been replaced by the current flash memory because it is difficult to erase and modify data, and the OTP type is expensive or low-cost and cannot modify data. Because flash is easy to erase and write, some of the current single-chip microcomputer support online internal programming, through a specific program execution method can modify falsh content, and realize online modification program memory. This is not in conflict with the content in the program memory mentioned above, which cannot be changed during running, because the content will not change during normal running of the program, it only works in read-only status.