What is the computer bus technology?

Bus, English is called "buses", that is, our Chinese "public car", which is very image, for example, the route of the public car is certain, any of us can take a public car to the route of any one of the public car site. If we compare our people to electronic signals, this is why English is called "bus" instead of "car". Of course, from a professional point of view, the bus is a description of electronic signal transmission lines of the structure of the form, is a set of signal lines, is the transmission of information between subsystems of the public channel. It can transfer, exchange, share and control the information between the parts of the whole system through the bus. such as in the computer system, it is CPU, memory, input, output devices to convey information of the public channel, the host parts through the host connection, the external equipment through the corresponding interface circuit and then connected to the bus.

　　

Classification

There are many ways of bus classification, such as external and internal bus, system bus and non system bus, etc.

By functional points

The most common is to partition the data bus from the function, which can be divided into address bus select、read (address buses), data bus and control bus. In some systems, the data bus and address bus can be shared under the control of the address latch, which is reused.

The address bus is specifically used to route addresses. In the design process, the most common should be from the CPU address bus select、read to choose the storage address of external storage. The number of bits in the address bus often determines the size of the storage space, for example, the address bus select、read is 16 bits, and its maximum storage space is 216 (64KB).

Data bus is used to transmit data information, it has one-way transmission and two-way transmission of data bus, two-way transmission of data bus is usually two-way three-state form of the bus. The number of digits in the data bus is usually consistent with the length of the micro-processing. For example, the Intel 8086 microprocessor has a length of 16 bits, and its data bus width is 16 bits. In the actual work, the data bus transmission is not necessarily the full meaning of the information.

The control bus is used to transmit control signals and timing signals. For example, when the microprocessor operates on the external memory, it must first emit a read/write signal, a slice signal and a read interrupt response signal through the control bus. The control bus is generally bidirectional, and its transmission direction is determined by the specific control signal, and the number of digits also depends on the actual control needs of the system.

Divide by transmission mode

The bus can be divided into serial bus and parallel bus according to the way of data transmission. In principle, the parallel transmission mode is better than the serial transmission, but the cost will be increased. In layman's terms, the parallel transmission path is like a multiple-lane road, while a serial transmission allows only one car to pass through a single road. At present, the common serial bus has SPI, I2C, USB, IEEE1394, RS232, can and so on, while the parallel bus is relatively small, common such as IEEE1284, ISA, PCI and so on.

Divide by clock signal mode

According to the clock signal is independent, can be divided into Stang and Line. Stang clock signals are independent of data, which means using a separate line as the clock signal, while the Line clock signal is extracted from the data, usually using the edge of the data signal as the clock synchronization signal.