#define SPH_PATTERN_INV ((SPH_CONFIGURABLE_BITS_BM & 0x55U) + INTERNAL_SRAM_START_8MSB)Applies the inverse checkerboard bit-pattern (0x55) to the configurable bits of the SPH register. Because the configurable bits of SPH are dependent on the size of SRAM, it is necessary to add the start address to compensate for any non-configurable bits when reading and writing to the SPH register.