The SMMA flag indicates whether a memory operation is already in progress. If it is 0, no memory operation is in progress. If it is 1, a memory operation is in progress. When the processor changes the state of SMMA from 0 to 1, the memory starts the operation. On completion of the operation, the memory control logic resets the flag. Obviously, this will be done after the memory access time is over. The MFC signal from memory can be used to reset this flag.