Encrypted Microcontroller PIC18F4480 Heximal Copying needs to crack mcu protective system and dump firmware out from flash and eeprom memory;
The action that takes place when the stack becomes full depends on the state of the STVREN (Stack Over- flow Reset Enable) configuration bit. (Refer to Section 23.1 “Configuration Bits” for a description of the device configuration bits.) If STVREN is set (default), the 31st push will push the (PC + 2) value onto the stack, set the STKFUL bit and reset the device. The STKFUL bit will remain set and the stack pointer will be set to zero when extract mcu atmega168l software.
If STVREN is cleared, the STKFUL bit will be set on the 31st push and the stack pointer will increment to 31. Any additional pushes will not overwrite the 31st push and STKPTR will remain at 31. When the stack has been popped enough times to unload the stack, the next pop will return a value of zero to the PC and sets the STKUNF bit, while the stack pointer remains at zero. The STKUNF bit will remain set until cleared by software or until a POR occurs if extract microcontroller atmega168a eeprom.
Returning a value of zero to the PC on an underflow has the effect of vectoring the program to the Reset vector, where the stack conditions can be verified and appropriate actions can be taken. This is not the same as a Reset, as the contents of the SFRs are not affected. Since the Top-of-Stack is readable and writable, the ability to push values onto the stack and pull values off the stack without disturbing normal program execution is a desirable feature before extract chip atmega88p program.
The PIC18 instruction set includes two instructions, PUSH and POP, that permit the TOS to be manipulated under software control. TOSU, TOSH and TOSL can be modified to place data or a return address on the stack. The PUSH instruction places the current PC value onto the stack. This increments the stack pointer and loads the current PC value onto the stack. The POP instruction discards the current TOS by decrementing the stack pointer. The previous value pushed onto the stack then becomes the TOS value.
