3. Communication Between Memory and Processing Unit

Communication between memory and processing unit consists of two registers:

• Memory Address Register (MAR).

• Memory Data Register (MDR).

To read,

1. The address of the location is put in MAR.

2. The memory is enabled for a read.

3. The value is put in MDR by the memory.

To write,

1. The address of the location is put in MAR.

2. The data is put in MDR.

3. The Write Enable signal is asserted.

4. The value in MDR is written to the location specified.