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general purpose processor[edit]The system designer only needs to program the processors memory to carry out therequired functionality: software portion.These types are created to produce large numbers for a variety of applications

Here are some general characteristics from a general purpose processor:

Advantages:easy to design and use (only programming the memory)design time is thus lowdesign cost is thus lowreprogrammability (changing functionalities or improving a system becomes easy when you only need to change the program)Disadvantages:performance is not very goodsize is high ( because they are built to be used in a variety of applications with different specifications and all these specifications must be possible on theprocessor)they consume much powerUsually they are used to put in a product the first time it goes to the market,because of their cheap design cost and ease to use.Because of the use of code, a designer usually strives to minimize compiled codesize, rather than maximize performance.

example:Microcontroller (MCU), MicroprocessorBasically a microprocessor performs all the tasks that must be accomplished by amicrocontroller/embedded system.A general microprocessor consists of a bus unit which is a pathway to communicate with the (computer) memory,an instruction cache to keep track of instructions coming from the computer memory through the bus unit,a (pre)fetch unit copying instructions from the instruction cache for further processing, a decode unit gettinginstructions from the prefetch unit that will be converted to a binary code understood by the processor,a control unit that performs tasks or instructions which are comprised in the binary code coming from the decode unit ,

data cacheto save instructions or data, an ALU (arithmetic logic unit) that executes mathematic operations such as adding, multiplying,and finally registers which are also some memory used by the ALU to store the results of performed operations.A microcontroller does not have a data bus or bus unit as described above for ageneral microprocessor.The reason is that there is no need to communicate to memory because memory is incorporated on the same chip as the microprocessor itself.A MCU is typically used as a systems controller, with many conditional operations and frequent changes in program flow. The MCU code is written in C or C++.Theres a wide variety of MCUs available: from 4-bit, 32 kHz models to 32-bit, 500MHz devices, and beyond(The "-bit" designation refers to the width of a device's data bus, registers, e

xecution units, etc.)

If you choose an embedded operating system (Windows, Linux, Dos...) a microprocessor is needed.But for real-time operations you better not use a microprocessor. The microcontroller is actually a low-end microprocessor,and is used in more simple tasks (traffic light to hold the light for a certaintime...)

single purpose processor[edit]

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This type of processor is designed to execute exactly one program. An embedded designer creates a single-purpose processor by designing a custom digitalcircuit Advantages and disadvantages are more or less the opposite of the general-purpose processor:

Advantages:performance is very goodsmall size (exact to fit one solution)they consume little powerDisadvantages:not very easy to design and design time is thus highdesign cost is thus higherreprogramming is difficultlimited flexibility: not easy to make changes, accommodate featuresIn design we can make a difference between standard single-purpose processors and custom single-purpose processors (ASSP). The standard single-purpose processors (hardware peripherals) are explained in a different chapter Hardware Peripherals. They are used for in a wide variety of applications for the same task.

example: application-specific integrated circuit (ASIC),application-specific standard product (ASSP)They are designed to fit the specific requirements of an end product. In the design process they will be optimised for both power and performance. An ASIC is introduced for a product usually after a product is stabilised on the market (with

non-ASIC solution), because of the higher development time and cost. After thestabilisation the producer can look for extra margin by making the processor asgood as possible for his application. A disadvantage is that when you make a mistake, you will need to make a whole new chip, but for a general-purpose processor you just change the code and recompile. You can use an ASIC in a stable marketwhere technology and requirements aren't going to change rapidly