According to the different types of information transmitted on the bus, the bus can be divided into what

According to the different types of information transmitted on the bus, the bus can be divided into "data bus", "address bus" and "control bus". The data bus is used to transmit data information, and can transmit data that needs to be processed or stored back and forth between the CPU and RAM. The address bus is used by the CPU or DMA-capable units to communicate the physical addresses of the components/places in the computer's memory that these units want to access. The control bus is used to transmit control signals and timing signals, and can transmit signals from the microprocessor control unit to peripheral devices.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

Bus (Bus) is a public communication trunk for transmitting information between various functional components of the computer. It is an internal structure. It is a common channel for CPU, memory, input and output devices to transmit information. Each of the host Components are connected through a bus, and external devices are connected to the bus through corresponding interface circuits, thus forming a computer hardware system. In a computer system, the common channel for transmitting information between various components is called a bus. Microcomputers use a bus structure to connect various functional components.

The bus is a transmission harness composed of wires. According to the type of information transmitted by the computer, the computer bus can be divided into data bus, address bus and control bus, which are used to transmit data, data address and control bus respectively. control signal.

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

• Address Bus: It is a CPU or a unit with DMA capabilities that is used to communicate that these units want to access (read/write) the physics of computer memory components/places. address.

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

Data bus DB

"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.

Common data buses are ISA (ISA bus), EISA, VESA, PCI, etc.

Address bus AB

"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, So the address bus is always unidirectional and tri-state, unlike the data bus. 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) 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

"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.

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