What is DRAM? What do you understand by DRAM refreshing? With the help of a block diagram, demonstrate how DRAM can be interfaced to a microprocessor.

Dynamic RAM (DRAM) is basically the same as SRAM, except that it retains data for only 2 or 4 ms on an internal capacitor. After 2 or 4 ms, contents of the DRAM should be completely rewritten (refreshed) as the capacitors, which store logic 1 or logic 0, lose their charges. Entire content of the memory is refreshed with 256 reads in a 2-to-4 ms interval. Refreshing also takes place during a write, a read or during a special refresh cycle.