Hardware system refers to thePhysical devices, that is, it is composed of mechanical, optical, electrical and magnetic components, and has the functions of calculation, control, storageinputandoutputThe physical part of the function.E.g. CPUstorage、floppy disk driver、Hard drive、Optical drive、mother boardVarious cards and host, display, printergraph plotter、ModemThe whole machine hardware is also called "hard equipment".along withElectronic systemThe complexity of,system designHas become an important discipline, traditionalRepeated test methodIt has become increasingly unfit for the development of the times.Fast-growingHardware/software co designTechnology is getting more and more attention.Under the guidance of system objectives and requirements, through comprehensive analysis of system software and hardware functions and existing resources, it maximizes the concurrency between system software and hardware, and coordinates the design of software and hardwareArchitectureTo make the system work in the best state.
One set for immediate usesystem bus All parts of the computer system are connected, and information can be exchanged between them through the bus.The advantage of this structure is that it is easy to expand newI/O deviceAnd various I/O devicesregisterAnd main memoryStorage unitsureUnified addressing, makeCPUAccess to I/O equipment is more convenient and flexible;The disadvantage is that only a pair of settings attached to the bus can transmit information to each other at the same time, that is, the bus is used in time sharing, which limits the throughput of information transmission. This structure is generally used inMicrocomputerandSmall computerMedium.
Dual bus structure
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In order to eliminate the bottleneck of information transmission, multiple groups of buses are often set. The most common is to set a dedicated high-speed bus between main memory and CPUStorage bus。The advantage of this structure is that the control circuit is simple and the transmission rate of I O bus is low;The disadvantage is that CPU efficiency is low, becauseI/O deviceInformation exchange with main memory shall be conducted through CPU.withstorageIn the dual bus structure,Main memoryIt can exchange information with the CPU through the storage bus, and can alsosystem bus Exchange information with I/O equipment. This structure has the advantage of high information transmission rate;Its disadvantage is that it needs to increase the investment in hardware.
Large system structure with channels
In order to expand the function of the system and improve the efficiency of the system, the channel structure is used in large and medium-sized computer systemshostMultiple channels can be connected, and one channel can connect one or more channelsI/OController, one I/O controller can be connected to one or moreI/O device, so it has greater expansion space. In addition, the channel manages and controls the I/O equipment, which reduces the CPU burden and improves the efficiency of the entire system.
Minimum hardware system
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The hardware design of embedded system is different from its application occasions and application systems.Generally, users can choose the appropriatemicroprocessorType, according to the corresponding interface circuit, different types of peripherals are collocated to form application systems with different purposes and different scales.These systems, no matter how large they are, can be divided into core circuits in terms of hardwareMinimum systemAnd variousperipheralThe required peripheral interface circuit.Usually, the smallest hardware system refers to a system composed of processors andSDRAMAnd FLASH, plus some necessaryAuxiliary circuitConstitute the core system.The minimum hardware system is not only the core part of the whole hardware system, but also its composition has an important impact on the software system. Its composition determines thatBootloaderAt the same time, it is also the basis for the normal operation of the embedded operating system.In other words, the smallest hardware system and the smallest software system at the bottom above it constituteEmbedded system The most basic and core part.
