0000nnnn11000011
r0 ← SignExtend32(R0);
op1 ← SignExtend32(Rn);
IF (AddressUnavailable(op1))
THROW WADDERR, op1;
IF (MMU() AND DataAccessMiss(op1))
THROW WTLBMISS, op1;
IF (MMU() AND WriteProhibited(op1))
THROW WRITEPROT, op1;
IF (MMU() AND NOT DirtyBit(op1))
THROW FIRSTWRITE, op1;
ALLOCO(op1);
address ← ZeroExtend32(op1);
WriteMemory32(op1, r0);