SECTION VI-8: Where the PIC Wakes Up when it is Powered Up

The question is that, at what address does the CPU wake up when power is applied? Each microprocessor is different. In the case of PIC family, all members of the family and variation, the PIC microcontroller wakes up at memory address 0000, when it is powered up. By powering up we mean applying Vcc to the RESET pin. 

When the PIC is powered up, the program counter PC has the value of 00000 in it. This means that it expects the first opcode to be stored at ROM address 00000H. In the PIC system, the first opcode must be burned into memory location 00000H of program ROM because this is where it looks for the first instruction when it is booted. We achieve this by using the ORG statement in the source program. Now discussing the step by step action of the program counter in fetching and executing a sample program in next sections.

PIC18 Program ROM Space
ipic18-program-rom-space.jpg

 

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