For memory operation, the CPU initiates a memory operation by loading the appropriate data i.e., address to MAR.

If it is a memory read operation, then it sets the read memory control line to 1. Then the contents of the memory location is brought to MDR and the memory control circuitry indicates this to the CPU by setting MFC to 1.

If the operation is a memory write operation, then the CPU places the data into MDR and sets the write memory control line to 1. Once the contents of MDR are stored in specified memory location, then the memory control circuitry indicates the end of operation by setting MFC to 1.

A useful measure of the speed of memory unit is the time that elapses between the initiation of an operation and the completion of the operation (for example, the time between Read and MFC). This is referred to as Memory Access Time. Another measure is memory cycle time. This is the minimum time delay between the initiation two independent memory operations (for example, two successive memory read operation). Memory cycle time is slightly larger than memory access time.