Microchip PIC18F44K20 Processor Flash Memory Program Restoration
Microchip PIC18F44K20 Processor Flash Memory Program Restoration is a reverse engineering process through which the fuse bit of MCU pic18f44k20 will be located and cracked, then extract locked code from microcontroller memory;
Under these conditions, the file address of the instruction is not interpreted as the lower byte of an address (used with the BSR in direct addressing), or as an 8-bit address in the Access Bank. Instead, the value is interpreted as an offset value to an Address Pointer, specified by FSR2. The offset and the contents of FSR2 are added to obtain the target address of the operation.
Any of the core PIC18 instructions that can use direct addressing are potentially affected by the Indexed Literal Offset Addressing mode. This includes all byte-oriented and bit-oriented instructions, or almost one-half of the standard PIC18 instruction set. Instructions that only use Inherent or Literal Addressing modes are unaffected.
Additionally, byte-oriented and bit-oriented instructions are not affected if they do not use the Access Bank (Access RAM bit is ‘1’), or include a file address of 60h or above. Instructions meeting these criteria will continue to execute to faciliate the process of attacking mcu pic18f13k50 flash memory. A comparison of the different possible addressing modes when the extended instruction set is enabled.
Those who desire to use byte-oriented or bit-oriented instructions in the Indexed Literal Offset mode should note the changes to assembler syntax for this mode. This is described in more detail in Section 24.2.1“Extended Instruction Syntax”.