Modes to have:

A. Immediate loads: values are inside instructions

B. Direct loads/stores: address is in instruction

C. Indirect loads/stores: address is in one of four Memory Pointer registers

D. Indirect loads/stores with offset: base address is in Memory pointer, while the 16-bit signed offset value is taken from General Purpose registers or from the word following the instruction

E. Indirect loads/stores with post-increment: same as C, only after memory access the memory pointer value gets incremented by value from GPR, or from the next word, or by one of pre-set values

F. Indirect loads/stores with pre-increment: same as D, but address in Memory Pointer gets updated before memory access

(probably some more?)

-- Loads and stores are to be mostly to and from General Purpose Registers.

-- Only way to load data into Memory Pointers and 8-bit registers from memory would be immediate values that are encoded into instruction.