Central CPU of single chip microcomputer scheme

In fact, people often combine arithmetic unit and controller, which is called central processing unit - CPU. In addition to the operation, the single chip microcomputer should also complete the control function. Therefore, it is inseparable from counting and timing. Therefore, a timer and counter are set in the single chip microcomputer. So far, we have known the basic composition of single chip microcomputer, that is, single chip microcomputer is composed of central processing unit (i.e. arithmetic unit and controller in CPU), read-only memory (usually expressed as ROM), read-write memory (also known as random memory, usually expressed as RAM), input / output port (also divided into parallel port and serial port, expressed as I / O port), etc. In fact, there is a clock circuit in the single chip microcomputer, so that the single chip microcomputer can operate and control rhythmically. In addition, there is the so-called "interrupt system", which has the function of "communication room". When the parameters of the single-chip microcomputer control object reach a state that needs to be intervened, it can be reported to the CPU through this "communication room", so that the CPU can take appropriate countermeasures according to the priorities of external events.

Now, we have known the composition of single chip microcomputer. The remaining problem is how to connect their parts into an interrelated whole? In fact, there is a "link" connecting them inside the single chip microcomputer, that is, the so-called "internal bus". This bus is like the "trunk road" of a big city, and CPU, ROM, ram, I / O port, interrupt system, etc. are distributed on both sides of this "bus" and connected with it. Thus, all instructions and data can be transmitted through the internal bus, just as all kinds of goods in a big city are transmitted through the trunk road.