The system bus of a computer is used to transfer information between various components of the computer and is divided into "data bus, address bus and control bus"; the system bus is a separate computer bus and is the main component connecting the computer system. The bus combines the functions of the data bus to carry information, the address bus to decide where to send the information, and the control bus to decide how to act.
The operating environment of this tutorial: Windows 10 system, DELL G3 computer.
What is it divided into: data bus, address bus and control bus?
System Bus (English: System Bus) is a separate computer bus and is the main component connecting computer systems. This technology was developed to reduce costs and promote modularity. The system bus combines the functions of the data bus to carry information, the address bus determines where to send the information, and the control bus determines how to act. Although the system bus was popular in the 1970s and 1980s, modern computers use different separate buses for more specific needs.
The information transmitted on the system bus includes data information, address information, and control information. Therefore, the system bus contains buses with three different functions,
That is, the data bus DB (Data Bus ), address bus AB (Address Bus) and control bus CB (Control Bus).
The data bus DB is used to transmit data information. The data bus is a bidirectional tri-state form (bi-directional means that it can be transmitted in two directions, either A->B or A
The address bus AB is specially used to transmit addresses. Since the address can only be transmitted from the CPU to the external memory or I/O port, the address bus is always one-way. Stateful, which is different from 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, if the address bus of an 8-bit microcomputer is 16 bits, its maximum addressable space is 2^16=64KB, and the address bus of a 16-bit microcomputer is 2^16=64KB. 20 bits, its addressable space is 2^20=1MB. Generally speaking, if the address bus is n-bit, the addressable space is 2^n (2 to the nth power) address space (storage unit). For example: a 16-bit wide address bus (commonly used in 8-bit processors in the 1970s and early 1980s) can address a memory space of 2 to the 16th power = 65536 = 64 KB addresses , and a 32-bit address bus (usually in PC processors like today's 2004) can address the memory space of 4,294,967,296=4GB (premise: the width of the data bus is 8 bits).
Note: bit=bit.
The B in the 2^n=X=YGB mentioned above is actually bit. This result is actually obtained by multiplying the addressable bits by 8 bits.
The 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 signal, bus request signal, limited 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.
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