Processor: The processor is the heart of embedded system. The selection of processor is based on the following consideration

• Instruction set
• Maximum bits of operation on single arithmetic and logical operation
• Speed
• Algorithms processing and capability
• Types of processor( microprocessor, microcontroller, digital signal processor, application specific processor, general purpose processor)

Power source:

Internal power supply is must. Es require from power up to power down to start time task. Also it can run continuously that is stay “On’ system consumes total power hence efficient real time programming by using proper ‘wait’ and ‘stop’ instruction or disable some unit which are not in use can save or limit power consumption.

Clock / oscillator Circuits:

The clock ckt is used for CPU, system timers, and CPU machine cycles clock controls the time for executing an instruction. Clock oscillator may be internal or external .It should be highly stable.

Real time clock(RTC):

It require to maintain scheduling various tasks and for real time programming RTC also use for driving timers, counters needs in the system.

Resets Ckts and power on reset:

Reset process starts executing various instruction from the starting address. The address is set by the processor in the program counter. The reset step resent and runs the program in the following way

• System program that execute from beginning
• System boot up program
• System initialization program

Memory :

A system embeds either in the internal flash or ROM, PROM or in an external flash or ROM or PROM of the microcontroller.