Ram, Rom, SRAM, ssram, SDRAM, flash memory

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 kind of storage will lose its storage content when the power is down, so it is mainly used to storeProgram.
According to different storage information, random memory is divided into static random memory (static RAM, SRAM) and dynamic random memory (Dynamic RAM, Dram ).

ROM:

Rom is short for read-only memory. It is a solid state semiconductor memory that can only read data stored in advance. The feature is that once data is stored, it cannot be changed or deleted. It is usually used in electronic or computer systems that do not need to change data frequently. The data will not disappear because the power supply is off.

SRAM:

SRAMYou can save the data stored internally without refresh the circuit. DRAM (Dynamic Random Access Memory)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.

◎Advantages and high speedYou do not need to use the memory refresh circuit to improve overall work efficiency.

◎Disadvantages: Low integration levelThe power consumption is large, the same capacity is large, and the price is high. A small number of key systems are used to improve efficiency.

◎Systems used by SRAM:

○ High-speed cache between CPU and primary memory.

○ CPU internal L1/L2 or external L2 cache.

○ Coast cache for external CPU expansion.

○ CMOS 146818 chip (RT & cmos sram ).

Ssram:

Ssram is the abbreviation of synchronous static random access memory, that is, synchronous static random access memory.

Synchronization refers to the step clock required for memory operations. The internal command transmission and data transmission are based on it. Random Index data is not stored in a linear order, instead, data is read and written by the specified address.

All access to ssram is started along the rise/fall of the clock. Address, data input, and other control signals are related to clock signals. Unlike asynchronous SRAM, asynchronous SRAM access is independent of the clock, and data input and output are controlled by address changes.

(SDRAM: synchronous dynamic random access memory, synchronous dynamic random access memory)

SDRAM:

Synchronous dynamic random memory with SDRAM

SDRAM: synchronous dynamic random access memory, which synchronizes dynamic random memory. Synchronization refers to the synchronization of clock for memory operations. Internal Command sending and data transmission are based on it; dynamic means that the storage array needs to be constantly refreshed to ensure that data is not lost. Random means that the index data is not stored in a linear order, but the data is read and written by freely specifying the address.

Flash memory:

Flash memory chip

flash memory is a long-lived non-volatile memory that maintains the stored data information during power outages, data deletion is not measured in a single byte but in a fixed block (Note: nor flash is stored in bytes .), The block size is generally kb to 20 mb. Flash memory is a variant of the electronic erasable read-only memory (EEPROM). Unlike flash memory, it can be deleted and rewritten horizontally in bytes instead of the entire chip, in this way, the flash memory is faster than the eeprom update speed. Because the data can still be stored during power-off, flash memory is usually used to save settings, such as in the computer BIOS (Basic Input and Output Program), PDA (Personal Digital Assistant), digital cameras to save data, etc.