存储器分类及主要指标

Classification of Memory Devices and Key Indicators

Classification Criteria	Type	Description
By Read-Write Function	Read-Write Memory	Allows CPU to read and write data, used for temporary data storage during system operation.
	Read-Only Memory (ROM)	CPU can only read pre-stored data in normal operation, used for storing firmware or system boot programs.
By Storage Medium	Semiconductor Memory	Stores information using the state of semiconductor circuits (e.g., flip-flops or capacitors), features fast access speed and small size, and is the main form of main memory.
	Magnetic Memory	Stores information using the magnetization direction of magnetic materials, has large capacity but relatively slow speed.
By Access Method	Random Access Memory (RAM)	The access time for any memory cell is the same, irrelevant to its physical location, which is the main feature of internal memory.
	Sequential Access Memory	Access time depends on the physical location of the data (e.g., tape, which requires rewinding), usually used for external memory.
By Information Retention	Volatile Memory	Information is lost immediately after power failure (e.g., common RAM).
	Permanent (Non-Volatile) Memory	Information is retained after power failure and does not require power to maintain (e.g., ROM, hard disk).

常用存储器芯片

扩展存储器设计

存储器地址译码电路设计

全地址译码

部分地址译码

存储器与 CPU 的连接