Memory is divided into read-only memory and read-write memory. The former stores debugged fixed programs and constants, and the latter stores some data that may change at any time. As the name suggests, once the read-only memory stores the data, it can only read out and cannot be changed (EPROM, E2PROM and other types of ROM can change and write data through certain methods - editor's note). The read - write memory can store or read data at any time

Internal structure of memory

How memory works

Memory is used to store data. It actually uses the high or low level to store data, that is, it actually stores the high or low level state, not what we are used to think

With such a structure, we can start storing data. For example, we need to put in a data

How does a number like 1234 work? Look at the figure above. This is the internal structure diagram of the memory. A memory is like a small drawer. There are 8 small boxes in a small drawer, that is, the 8-bit small boxes of the single chip microcomputer. Each small box is used to store 1-bit charge. The charge is transmitted or released through the wire connected to it. As for how the charge is stored in the small box, I don't need to know You can think of the wire as a water pipe. The charge in the small box is like water. That's good to understand. We call it a small drawer in the memory. One unit is equivalent to one byte, and one small box is equivalent to one bit 00011010. We just need to fill the small boxes No. 2, No. 4 and No. 5 with charge and let go of the charge in other small boxes, but the problem comes out again A memory has many same cell lines in parallel. Look, d7-d0 will put the charge into all byte cells when putting the charge, and the charge in each cell will be released when releasing the charge. In this way, no matter how many byte cells there are in the memory, we can only put the same number. Of course, this is not what we want, so we need to make a slight change in the structure There is a line connected to the decoder on each unit of the diagram. I send a signal to which unit through the decoder if I want to put the data into. The decoder turns on the corresponding switch through this line, so that the charge can go in and out freely. So can I write or read out the data to the memory at will? In fact, I can't continue to look at the figure above and d7-d 0 is also connected to a controller. What is it used for? This line is called the write / read control line. When we write data to the memory, we must first switch the switch to the write end. When we want to read data, we must first switch the switch to the read end. The chip selection end is to distinguish different memory settings. It doesn't matter if we don't understand it. Let's take a look at it later See how the decoder works