Image Number 3 for United States Patent #6260157.
A processing device includes a ROM having program instructions and at leas one jump instruction stored therein, a patch program for patching the program instructions in the ROM, a RAM capable of storing the patch program and a patch vector table that indicates the location of the patch program. A processor executes the program instructions in the program ROM and uses the patch vector table to execute the patch program when one of the jump instructions is reached. The patch program may be stored in the RAM and the patch vector table may point to the address in the RAM at which the patch program is stored so that the processor jumps directly to the RAM to execute the patch program when it reaches the one of the jump instructions. Likewise, a patch engine may be used to locate a specified patch program, load the specified patch program into the RAM and execute the specified patch program when the processor reaches the one of the jump instructions.