Instructions that use indexed addressing with 16-bit offsets can read from or write to any location in the 68HC05 memory map. These instructions always require three bytes of storage.
Target addresses are formed by taking the unsigned sum of the 16-bit offset and the contents of the index register and always range from $0000 to $FFFF. Thus, if X = $41, the instruction STA $FFE0,X will write to address $0021.
Indexed addressing with 16-bit offsets is especially useful for accessing tabular or string data stored in on-chip ROM which, on most 68HC05 devices, resides primarily above $0100.
