PIC18F4510 Microprocessor Encrypted Heximal Reading has been proved to be success by executing a security fuse bit breaking on the microcontroller, the content readout from its MCU is perfectly matched with original file;
Device Resets on stack overflow and stack underflow conditions are enabled by setting the STVREN bit in Configuration Register 4L. When STVREN is set, a full or underflow will set the appropriate STKFUL or STKUNF bit and then cause a device Reset. When STVREN is cleared, a full or underflow condition will set the appropriate STKFUL or STKUNF bit but not cause a device Reset. The STKFUL or STKUNF bits arecleared by the user software or a Power-on Reset when extract mcu atmega169v flash content.
A fast register stack is provided for the Status, WREG and BSR registers, to provide a “fast return” option for interrupts. The stack for each register is only one level deep and is neither readable nor writable. It is loaded with the current value of the corresponding register when the processor vectors for an interrupt. All interrupt sources will push values into the stack registers. The values in the registers are then loaded back into their associated registers if the RETFIE, FAST instruction is used to return from the interrupt if the firmware of microcontroller ic can be extracted.
If both low and high priority interrupts are enabled, the stack registers cannot be used reliably to return from low priority interrupts. If a high priority interrupt occurs while servicing a low priority interrupt, the stack register values stored by the low priority interrupt will be overwritten. In these cases, users must save the key registers in software during a low priority interrupt.If interrupt priority is not used, all interrupts may use the fast register stack for returns from interrupt before the MCU binary has been read from eeprom.
If no interrupts are used, the fast register stack can be used to restore the Status, WREG and BSR registers at the end of a subroutine call. To use the fast register stack for a subroutine call, a CALL label, FAST instruction must be executed to save the Status, WREG and BSR registers to the fast register stack. A RETURN, FAST instruction is then executed to restore these registers from the fast register stack. Example 5-1 shows a source code example that uses the fast register stack during a subroutine call and return.
