Basic components of memory
Discussed herein is main memory, i.e. memory.
The main memory includes a storage body, MAR, MDR, the various components and logic control circuits.
Bank
- A main memory (memory) composed of a plurality of memory banks, a bank has a plurality of memory cells, one memory cell has several (8,16,32 etc.) of memory elements;
- Each storage element can store a binary "0" or "1";
Storage memory word length word
- Word storage : a storage unit for storing binary code;
- Memory word length : number of binary code stored in a memory cell; memory word length may be 8, 16, 32 and the like.
A memory word may represent a binary number, decimal, hexadecimal number, a string of characters, ASCII code, such as an instruction.
Such as: 0011011001111101 memory word represents the binary number 16, 13949 represents a decimal, hexadecimal numbers 367DH, two ASCII code indicates "6" and "}" represents an instruction.
Instructions and data stored in a memory;
Search by address
- Search by address : an address given to each memory cell number, address number according to realization of the memory storage unit memory word (written), taken (read).
As will be prepared in advance of each instruction stored in the respective program good storage unit, when the program is run, as long as the first address of the first instruction given by the program in the main memory, the program counter is incremented and the method 1, the automatic formation address storage unit storing an instruction, the machine can automatically run the whole process.
As another example, when the need to reuse one of an instruction or data, is sufficient to point their respective address numbers to the memory cell, without taking up more memory cells to store the same data or repeat the same instruction, thereby increasing the utilization of storage space.
Two registers
The MAR ( Memory the Address the Register ), a memory address register.
- Action: a storage unit storing an address (number).
- The number of bits of the memory cell corresponding to the MAR. For example, if the storage unit has 1024 = 2 10 th, 10 has the MAR.
- MAR reflect the number of memory cells.
MDR (the Register the Data Memory), a memory data register.
- Action: storing data stored in the memory cell preparation, or store data from the storage unit to the CPU is ready to remove.
- MDR is equal to the number of bits stored in word length.
- MDR reflect storage word length, and the length of a single cell.