0100nnnn00000011
md ← ZeroExtend1(MD);
IF (md = 0)
THROW RESINST;
sr ← SignExtend32(SR);
op1 ← SignExtend32(Rn);
address ← ZeroExtend32(op1 - 4);
WriteMemory32(address, sr);
op1 ← address;
Rn ← Register(op1);