How to Choose a

Micro Controller?

What is a "Microcontroller" ?A microcontroller is a small computer on a

single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications.

Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems.

Selecting a MicrocontrollerThe selection of microcontrollers involves the following factors.

1. Number of Input/output PinsHow many input/output pins are needed for the task concerned?

2. Interfaces requiredWhat Interfaces are going to be required?For example, is PWM required? Many Microcontrollers have PWM outputs, e.g. the PIC17C42 has two.

3. Memory requirementsWhat size memory is required for the task? The size of memory may be an important consideration. Some micros have as few as 256 instructions and 16 bytes of RAM. You can do a lot in that sort of space, but not everything. Moreover, while you can frequently upgrade to a "bigger chip", some chip families have relatively small memory limits imposed by their architecture,

so even the biggest chip you can get will have only 8k instructions (for example.) RAM (data memory) is usually scarce in microcontrollers; some algorithms require substantial RAM to be implemented in a straightforward manner, and it may be worthwhile looking for a micro with a lot of RAM (or external RAM expansion capabilities) if that's the sort of thing you had in mind. (For instance, implementing TCP/IP networking protocols in a micro whose total RAM space is less than used by a typical ethernet packet is likely to be ... interesting.)

4. Number of Interrupts requiredHow many events will need interrupts?

5. Processing speed required The microprocessor takes time to execute instructions, this time being determined by the processor clock.

Selecting a Microcontroller….

6. Cost – HW/SW tradeoffs7. Power consumption - TI, Microchip, Freescale9. Analog – A/D, DAC, Comparator, Op-amp10. Serial Communication- SPI, I2C, USB, IR, GbE 11. Product Family12. Development tools13. Timers – input capture, output compare14. Environmental conditions

Selecting a Microcontroller….

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