Can any one tell me exactly what is a boot loader in a microcontroller

 

Google probably would do a better job than me at explaining but in summary it is a piece of code on the MCU that checks for incoming data of a specific format every time the processor is reset. If it receives this data it copies it into the MCU program memory at an address beyond the bootloader code (to avoid overwriting the bootloader) and then executes it. If no data is received it starts executing what ever code is currently in memory at the start address.

In this way it allows an MCU to be programmed over serial lines (usually via USB) without dedicated programming hardware.

 

Thank you very much....I don't have much idea about controller...But it is mentioned that it is piece of code on MCU.....for which processor resets....I have a doubt does MCU will have a processor in it...If so what is the differnce between controller and processor

 

Thank you Nandu

 

All micoprocessors and microcontrollers have internal hardware to accomplish a RESET function. In short this function resets all of the internal registers to some set of known default values. You can find these known default values in the datasheet. It then sets the program counter register to the address of the NEXT instruction to be executed. It then lets the processor do what it does, fetch instructions and execute them.

This first program that gets executed could be a bootloader or it could be the ultimate application.

 

We covered this here, twice already:

http://forum.allaboutcircuits.com/threads/firmware-in-microcontroller.103949/