Semiconductor memories and auxiliary memories

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MEMORY UNIT-3 Mohammad Asif Iqbal Assistant Professor, Deptt of ECE,

Transcript of Semiconductor memories and auxiliary memories

Page 1: Semiconductor memories and auxiliary memories

MEMORY

UNIT-3

Mohammad Asif IqbalAssistant Professor, Deptt of ECE,JETGI, Barabanki

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SEMICONDUCTOR MEMORY

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INTERNAL ORGANIZATION OF MEMORY CHIP

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TOTAL EXTERNAL CONNECTIONS 16 words of 8 bits each:16x8 memory org..TOTAL EXTERNAL CONNECTION=164 ADDRESS (A0 A1 A2 A3)8DATA (b0 b1 b2 b3……………………b7)2 CONTROL 2 POWER/GROUND

1Kx1 memory cells ???

128x8 memory???

= 15

= 19

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CONTINUED……….

32 ROWS

32 COLUMNSInput/output

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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

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SRAM

READ

ON ONWRITE1 0

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EXAMPLE OF A CMOS MEMORY CELL

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CMOS INVERTER

0 ON1 ON

NMOS

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EXAMPLE OF A CMOS MEMORY CELL

1 0

1ON

1OFF

0OFF

0ON

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ASYNCHRONOUS DRAMS

T

The charge may be stored for 10 ms only

bWord line 5V= LOGIC 1

ON

CHARGING

OFF

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& 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

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& 2.5 OR 2 1/2D MEMORY ORGANIZATION2D

32 ROWS

32 COLUMNSInput/output

64 only

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ROMZ0 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

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PROMBIT LINE

WORD LINE

FUSE LINK

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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??

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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.

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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.

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AUXILIARY MEMORIES

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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 thedirection that

the current flows

How a magnetic recording works

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MAGNETIC TAPE

8 TRACKS (DATA) + 1 PARITY

READ/WRITE HEADBLOCK 1

BLOCK 2IRG

INTER RECORD GAP

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FLOPPY OR MAGNETIC DISC

READ/WRITE HEAD

We may have single sided floppyDouble sided floppy

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MAGNETIC DISC

Head no: 3Cylinder no: 0Sector no: 1

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THANK YOU!