In these slides the concept of semiconductor memories have been explained in detail. With the clear dramatisation of CMOS logics. Auxiliary memories and its type have also been discussed.

1. MEMORY
UNIT-3
Mohammad Asif Iqbal
Assistant Professor,
Deptt of ECE,
JETGI, Barabanki

2. SEMICONDUCTOR MEMORY

3. INTERNAL ORGANIZATION OF MEMORY CHIP

4. TOTAL EXTERNAL CONNECTIONS
16 words of 8 bits each:
16x8 memory org..
TOTAL EXTERNAL CONNECTION=16
4 ADDRESS (A0 A1 A2 A3)
8DATA (b0 b1 b2 b3……………………b7)
2 CONTROL
2 POWER/GROUND
1Kx1 memory cells ???
128x8 memory???
= 15
= 19

5. CONTINUED……….
32 ROWS
32 COLUMNS
Input/output

6. SOME MORE PROBLEMS
A computer uses RAM chips of 1024 x 1 capacity.
a) How many chips are needed and how should their address lines be connected to provide a
memory capacity of 1024 bytes?
b) How many chips are needed to provide a memory capacity of 16K bytes?
Explain in words how the chips are to be connected to the address bus.
1024X1 1024X1 1024X1 1024X1 1024X1 1024X1 1024X1 1024X1
1024 bytes = 1024 X 8 bits = X 8
1024

7. SRAM
1 0

8. EXAMPLE OF A CMOS MEMORY CELL

9. CMOS INVERTER
0 ON
1 ON
NMOS

10. EXAMPLE OF A CMOS MEMORY CELL
1 0
1
ON
1
OFF
0
OFF
0ON

11. ASYNCHRONOUS DRAMS
T
The
charge
may be
stored
for 10 ms
only
b
Word line 5V= LOGIC 1
ON
CHARGING
OFF

12. & 2.5 OR 2 1/2D MEMORY ORGANIZATION
Suppose that the MAR is
10 bits wide
1024 words in the memory.
While this is not necessarily
terrible, increasing the MAR to
15 bits means there will be
32,768 wires, and 20 bits
would be over a million.
2D

13. & 2.5 OR 2 1/2D MEMORY ORGANIZATION2D
32 ROWS
32 COLUMNS
Input/output
64
only

14. ROM Z0 Z1 Z2 Z3
W0
W1
W2
W3
Z0 Z1 Z2 Z3 W0 W1 W2 W3
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1

15. PROM
BIT LINE
WORD LINE
FUSE LINK

16. QUESTIONS..
1-A ROM chip has four select inputs and operates from a 5V power
supply. How may pins are needed for the IC package? Draw the block
diagram and labeled all the input and output terminals in the ROM.
2-A peacock is a bird that doesn't lay eggs. How do they gets baby
peacocks??

17. EPROM :-Erasable, reprogrammable ROM
They may store information for long time but
not for infinite time some says for 100 years So
they may be used in place of ROM.
In this we use a special type of transistor
known as FAMOS.
The special characteristic of this transistor is
that it may be used as a normal transistor or as a
disabled transistor that is always turned off.
The important advantage of EPROM chip is
that their content can be erased and
reprogrammed
For erasing we have to erase the charges
trapped in the transistor of the memory cell;
which is achieved by exposing it to the
Ultraviolet light. This is the reason of this
transparent window.

18. EEPROM
A significant disadvantage of EPROMS is that a chip must be
physically removed from the circuit for reprogramming and
that its entire contents are erased by the ultraviolet light.
So an other ROM came into existence that can be both
programmed and erased electrically. Such chips are called
EEPROM( Electrically erasable PROM)
Moreover it is possible to erase the cell content selectively.
The only disadvantage of EEPROM is that different voltages
are needed for erasing, writing and reading the stored data.

19. AUXILIARY MEMORIES

20. The resulting magnetic field can be in
one of two different orientations
(polarities):
North-South
(clockwise)
South-North
(counter-clockwise)
A moving electrical
charge (current) creates a
magnetic field...
depending on the
direction that
the current flows
How a magnetic recording works

21. MAGNETIC TAPE
8 TRACKS
(DATA)
+ 1 PARITY
READ/WRITE
HEAD
BLOCK 1
BLOCK 2
IRG
INTER RECORD GAP

22. FLOPPY OR MAGNETIC DISC
READ/WRITE
HEAD
We may have single sided floppy
Double sided floppy

23. MAGNETIC DISC
Head no: 3
Cylinder no: 0
Sector no: 1

24. THANK YOU!