What are the three types of computer buses?

The computer bus can be divided into data bus, address bus and control bus. The data bus transfers data that needs to be processed or stored back and forth between the CPU and RAM; the address bus is used to specify the address of the data stored in RAM; the control bus transmits signals from the microprocessor control unit to peripheral devices.

Computer bus can be divided into data bus (Data Bus), address bus (Address Bus) and control bus (Control Bus), also collectively referred to as the system bus .

• Data Bus: Transfers data that needs to be processed or stored back and forth between the CPU and RAM.

• Address Bus: Used to specify the address of data stored in RAM (Random Access Memory).

• Control Bus: Transmits signals from the microprocessor control unit (Control Unit) to peripheral devices.

"Data bus DB" is used to transmit data information. The data bus is a bidirectional three-state bus, that is, it can transmit data from the CPU to other components such as memory or I/O interfaces, and can also transmit data from other components to the CPU. The number of bits in the data bus is an important indicator of a microcomputer and is usually consistent with the word length of the microprocessor. For example, the word length of the Intel 8086 microprocessor is 16 bits, and its data bus width is also 16 bits. It should be pointed out that the meaning of data is broad. It can be real data, instruction code or status information, and sometimes even control information. Therefore, in actual work, what is transmitted on the data bus is not necessarily Just real data.

"Address bus AB" is specially used to transmit addresses. Since addresses can only be transmitted from the CPU to external memory or I/O ports, the address bus is always one-way three-state, which is different from the data bus. different. The number of bits in the address bus determines the size of the memory space that the CPU can directly address. For example, the address bus of an 8-bit microcomputer is 16 bits, so its maximum addressable space is 2^16=64KB. A 16-bit microcomputer (x-bit processing The address bus refers to the number of bits (1, 0) that the microprocessor can process in one clock cycle, that is, the word size). The address bus is 20 bits, and its addressable space is 2^20=1MB. Generally speaking, if the address bus is n bits, the addressable space is 2^n bytes.

"Control bus CB" is used to transmit control signals and timing signals. Among the control signals, some are sent by the microprocessor to the memory and I/O interface circuits, such as read/write signals, chip select signals, interrupt response signals, etc.; some are fed back to the CPU by other components, such as: interrupt application signals, reset signals, bus request signals, device ready signals, etc. Therefore, the transmission direction of the control bus is determined by the specific control signal, (information) is generally bidirectional, and the number of bits on the control bus is determined according to the actual control needs of the system. In fact, the specific situation of the control bus mainly depends on the CPU.

The above is the detailed content of What are the three types of computer buses?. For more information, please follow other related articles on the PHP Chinese website!