Question

Course: Computer Architecture
Theme: Internal Memory

Draw the diagram of a typical 16 Mb DRAM (4M X 4) and explain its action. Draw the diagram of an SRAM cell and explain its action.

Answer 1

16 Mb DRAM (4M X 4)

DRAM means dynamic random access memory. The DRAM has more advantages than static RAM like simpler to build, less expensive, larger memory units, etc. DRAM is a special type of memory where it stores each bit in a cell containing capacitors and transistors.

In 16 MB DRAM at a time we can able to read/write 4bits. The memory is organized by 4 squares of array with2048 X 2048 elements. The system can able to select each location by specifying the row address and column address.

Working

As u can see above, this shows the architecture of 16 Mb DRAM. When the system needs to read data then the system supplies the address this is carried to the DRAM using address lines. 11 lines are needed to select one block in 2048 rows. Once the address is received by the DRAM it will feed into the row decoder to decode the address. The same procedure is carried out in a column decoder. After decoding the output is fed into the memory array and the memory array will return the data..

SRAM cell

SRAM is a static random access memory that uses circuits that contain latches to hold the bits.

Working

The above figure shows the architecture of the SRAM cells. Each SRAM contains 2 states- state 0 and state 1.

in state 0

c1is low(0) and c2 is high(1)

T2,T3 OFF and T1,T4 is on

in state 1

c1is high(0) and c2 is low(1)

T2,T3 On and T1,T4 is off

To write into SRAM:- apply values to bit line B and B'

To read from SRAM:-apply value to bit line B