Bus is an internal structure and a common channel for cpu, memory and input/output devices to transmit information. All components of the host computer are connected through the bus, and external devices are connected to the bus through corresponding interface circuits, thus forming a computer hardware system. In the computer system, the common path for transmitting information among various components is called bus, and the microcomputer connects various functional components through the bus structure.
Address bus AB(Address Bus): used to specify the address of data stored in RAM (Random Access Memory).
A computer bus is a unit that supports CPU or DMA and is used to transfer the physical addresses of computer memory components/locations that these units want to access (read/write). The width of data bus varies with the size of addressable memory components, which determines how much memory can be accessed.
1, and the address bus AB is specially used to transmit addresses. Because the address can only be transmitted from CPU to external memory or I/O port, the address bus is always unidirectional and tri-state, which is different from the data bus.
The number of bits in the address bus determines the memory space that the CPU can directly address. For example, the address bus of an 8-bit microcomputer is 16 bits, and its maximum addressable space is 2 16 = 64 KB. The address bus of an 8-bit microcomputer 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 bits.
2. Control Bus CB (Control Bus): It transmits the signal of the microprocessor control unit to the peripheral equipment.
Control bus (CB for short). The control bus is mainly used to transmit control signals and timing signals. Some of these control signals are sent by the microprocessor to the interface circuits of memory and input/output devices, such as read/write signals, chip selection signals and interrupt response signals. There are other components that feed back to the CPU, such as: interrupt application signal, reset signal, bus request signal, device ready signal, etc.
Therefore, the transmission direction of the control bus depends on the specific control signal, which is generally bidirectional, and the number of bits of the control bus depends on the actual control needs of the system. In fact, the specific situation of control bus mainly depends on CPU. ?
Control buses are connected together to complete and realize the communication and data transmission between them, so the concept of bus is the basis for understanding the composition and working principle of PC and motherboard and the interrelated system between components.
These control information include CPU's reading and writing signals to memory and I/O interface, I/O interface's interrupt request or DMA request signal to CPU, CPU's reply and response signal to these I/O interfaces, various working status signals of I/O interface and other various functional control signals. The control bus runs between CPU, memory and input/output devices.
3. Data bus DB(Data Bus): Data is transmitted between CPU and RAM for processing or storage.
A bus. Standardize the realization method of data sharing and exchange between homogeneous system and heterogeneous system in large-scale integrated application system, and the data exchange standard between systems. It can be used to transfer information between microprocessor and memory, and between microprocessor and input/output interface. The width of data bus is an important index to determine the performance of computer. At present, the data bus of microcomputer is mostly 32 bits or 64 bits.
Business entity data exchange: each subsystem has a business entity layer in the architecture level, and the data exchange mechanism establishes a layer transparent to all application systems at the business entity layer. Subsystems can share and interact through the business entity layer, no matter what the specific technical scheme is, which establishes a structure for continuous integration and business expansion between subsystems, thus realizing an extensible and complete integrated information system.
WebService data exchange: It is a Web service standard. Web service provides a scheme to share and exchange data between heterogeneous systems, and it can also share and exchange data by using unified interface standards in product integration.
Extended data
Technical indicators
1, the bandwidth of the bus (bus data transmission rate)
The bandwidth of the bus refers to the amount of data transmitted on the bus per unit time, that is, the maximum steady-state data transmission rate MB per second. [2]。 Two factors closely related to the bus are the bit width of the bus and the working frequency of the bus, and their relationship:
Bus bandwidth = bus working frequency * bus bit width/8;
Or the bandwidth of the bus = (bit width of the bus /8 )/ bus period.
2. Bit width of the bus
The bit width of the bus refers to the number of bits of binary data that can be transmitted by the bus at the same time, or the number of bits of the data bus, that is, the concept of bus width such as 32 bits and 64 bits. The wider the bit width of the bus, the greater the data transmission rate per second and the wider the bandwidth of the bus.
3. Operating frequency of the bus
The working clock frequency of the bus is in MHZ. The higher the working frequency, the faster the bus works and the wider the bus bandwidth.
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