3.10 Program Memory with Post-increment using the LPM Z+ and ELPM Z+ Instruction
Constant byte address is specified by the Z-pointer contents. The 15 MSbs select word address. The LSb selects low byte if cleared (LSb == 0) or high byte if set (LSb == 1). If ELPM Z+ is used, the RAMPZ Register is used to extend the Z-register.