mistake. Buses can be divided into five types according to their functions: 1. Data bus, which is used to transmit data information. The data bus is a bidirectional three-state bus that transmits data that needs to be processed or stored back and forth between the CPU and RAM; 2. Address bus, used to specify the address of the data stored in RAM; 3. Control bus, It is mainly used to transmit control signals and timing signals; 4. Expansion bus is a bus for data communication between external devices and the computer host; 5. Local bus is a first-level bus or management layer added between the ISA bus and the CPU bus.
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 a transmission harness composed of wires.
The bus is an internal structure. It is a common channel for CPU, memory, input and output devices to transmit information. The various components of the host are connected through the bus, and the external devices are connected to the bus through the 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.
Bus can be divided into five types according to their functions and specifications:
Data Bus: In the CPU Data that needs to be processed or stored is transferred back and forth to 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.
Expansion Bus: A bus for data communication between external devices and the computer host, such as ISA bus and PCI bus.
Local Bus: An expansion bus that replaces higher-speed data transmission.
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.
Data Bus (DataBus) standardizes the implementation method of data sharing and exchange in homogeneous systems and heterogeneous systems in a large integrated application system, and the standard for data exchange between systems. It can be used to transfer information between microprocessor and memory, microprocessor and input and output interface. The width of the data bus is an important indicator of computer performance. Microcomputer data buses are mostly 32-bit or 64-bit.
1. Business entity data exchange: Each subsystem has a business entity layer in the architecture layer. The data exchange mechanism establishes a layer in the business entity layer that is transparent to all application systems. layer. Subsystems, regardless of the specific technical solutions implemented, can share and interact through the business entity layer. This also establishes a structure that can carry out continuous integration and business expansion between subsystems, thereby achieving an scalable a complete integrated information system.
2. WebService data exchange: It is a Web service standard. Web service provides a solution for sharing and exchanging data between heterogeneous systems. It can also be used to use unified data in product integration. Interface standards for data sharing and exchange.
Address bus AB
"Address bus AB" is specially used to transmit addresses, because addresses can only be transmitted from the CPU to external memory or I/O port, 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
ControlBus (ControlBus) is referred to as CB. The control bus is mainly used to transmit control signals and timing signals. Among the control signals, some are sent by the microprocessor to the memory and input and output device 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 request signals, Reset signal, bus request signal, device ready signal, etc. Therefore, the transmission direction of the control bus is determined by the specific control signal, which is generally bidirectional. The number of bits in 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 control bus is connected together and completes and implements communication and data transmission between them. Therefore, the concept of bus is the basis for understanding the structure, working principle and mutual relationship between components of PC and motherboard. These control information include the CPU's read and write signals to the memory and input and output interfaces, the interrupt requests or DMA request signals from the input and output interfaces to the CPU, the CPU's answer and response signals to these input and output interfaces, and the various working status signals of the input and output interfaces. and various other function control signals. The control bus travels between the CPU, memory, and input and output devices.
Extension bus
The expansion bus is a set of transmission lines that transmit information from one or more source components to one or more destination components.
Expansion bus type:
PC/XT bus system
In the early 1980s, with the emergence of IBM PC/XT, The 8-bit expansion bus it used represented a new bus standard at the time. This model quickly dwarfed the Apple ΙΙ.
With the improvement of peripheral device performance, main memory speed and 16-bit central processor performance, the 8-bit bus can no longer adapt to new technologies. IBM used Intel to launch a new 16-bit microprocessor 80286 development PC/AT personal computers use a new 16-bit expansion bus, which is formed by adding address signals, data signal lines and control signal lines to the PC/XT expansion bus. These two buses have coexisted on the same chassis for a long time. .
ISA bus system
The extended bus system of PC/AT is the industry standard architecture that has been used in the market for a long time. Bus (ISA). This 16-bit expansion bus system has been the mainstream used by motherboard manufacturers on the market for a long time. Some people tried to establish another standard, but they were eliminated by the market (this situation continued until the emergence of 32-bit microprocessor chips) after).
Local bus
The local bus is a first-level bus or management layer added between the ISA bus and the CPU bus. This allows some high-speed peripherals. Such as graphics card. The hard disk controller is removed from the ISA bus and directly connected to the CPU bus through the local bus to match the high-speed CPU bus.
Local bus technology is a major change in the development of PC architecture. It has made a qualitative leap in the data exchange speed between peripherals, CPU and memory. The performance difference between PCs and small workstations has gradually disappear.
High-performance microprocessors can run at clock frequencies above 33MHz, but they still have to wait for hard drives, graphics cards and other peripherals. The single-bus system structure has become a bottleneck in improving the overall performance of microcomputers. In order to solve this problem, a local bus is added to the traditional bus structure to improve the overall performance of the machine. The currently implemented local buses can be divided into dedicated local buses, VESA local buses and PCI local buses.
The "local bus" defined by the VESA bus directly connects address, data and control signals to the pins of the main CPU. The bus design is simple and has no buffer. When the CPU speed is higher than 33MHz, it will cause processing delays and generate wait states. Therefore, it can only reliably control three peripherals.
The starting point of the PCI local bus design is to improve the interconnection of peripheral components, hoping that it will become a cross-platform/cross-processor universal I/O component interface standard. Therefore, the PCI bus is independent of the bus and connected to the CPU management The feet have nothing to do with it. Adopting group mode, linear burst transmission, bus master control and synchronous operation are possible. It has strong compatibility with other buses and provides automatic configuration function.
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