Memory Unit

The basic processing of a computer begins with memory fetch or read cycle and the memory fetch is routed to the memory unit.

The memory unit consists of a large number of storage locations each with its own unique address. The CPU can randomly access any location in memory where RAM is often used. And this memory organization is typical for most microprocessors today. RAM being a volatile memory there should be power for the memory to contain data so a portion of memory unit is often built using read-only memory (ROM) chips. The program stored by a ROM is permanent and is not lost when power is removed. The memory unit’s address selector/decoder circuit examines the binary number on the address lines and selects the proper memory location to be accessed. In example, CPU is reading from memory, it activates its Memory Read control signal. This causes the selected database in memory to be placed onto the data lines and routed to the instruction register within the CPU. This is how memory unit works.