A limit switch controlling method and apparatus used in an optical drive are disclosed. The step of forming the embedded well region includes simultaneously doping the embedded well region and a well region of a core regular MOS device, and simultaneously doping the embedded well region and a well region of an IO regular MOS device, wherein the core and IO regular MOS devices are of the first conductivity type. If the destination verification module receives an acceptable version from the source, the destination module then determines a base PCPI to utilize for verification and sends a PCPI identifier of the base PCPI to the source.