Principles of Digital Electronics€¦ · Principles of Digital Electronics Chapter 06 Memories ... semiconductor memories. (True or False) True 3. Generally, if a semiconductor memory

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Principles of Digital

Electronics

Chapter 06

Memories

Mr. Nikhil Satpute


INTRODUCTION

• Overview of Memory

• Random Access Memory (RAM)

• Read Only Memory (ROM)

• Programmable ROM (PROM)

• Nonvolatile Read/Write Memory

• Memory Packaging

• Computer Bulk Storage Devices

• Digital Potentiometer with NV EEPROM


Classification of Memories

Memory

RAM (Random Access

Memory)

SRAM (Static RAM)

DRAM (Dynamic

RAM)

ROM (Read Only

Memory)

Masked ROM PROM EPROM EEPROM Flash

EEPROM

Sequential Memories


• Density

- Amount of data that the memory can store

• (Non-) Volatility

- Data storage capability if power is disconnected

• Read/write capability

- Capability to update memory

Overview of Memory

Three Important Characteristics

of Semiconductor Memory:


QUIZ

1. Three important characteristics of

semiconductor memory are (1) density, (2)

non-volatility, and (3) a read/write capability.

(True or False) True

2. High density (small memory cell size) is a

desirable characteristic of modern

semiconductor memories. (True or False) True

3. Generally, if a semiconductor memory is

nonvolatile this is a desirable characteristic.


4. A semiconductor memory that can be updated

is referred to as a(n) __________ (read-only,

read/write) memory.

read/write


• DRAM (Dynamic Random-Access Memory)

• SRAM (Static Random-Access Memory)

• ROM (Read-Only Memory)

• EPROM (Electrically Programmable ROM)

• EEPROM (Electrically Erasable PROM)

• Flash Memory

• FRAM (Ferroelectric RAM)

• MRAM (Magnetoresistive RAM)

Overview of Memory (Continued)

See future slides for characteristics of each category of memory.

Categories of Semiconductor Storage Cells:


QUIZ

1. SRAM is an acronym for _______. Static Random-

Access Memory

2. ROM is an acronym for _______. Read-Only Memory

3. DRAM is an acronym for ______. Dynamic Random-

Access Memory

4. EEPROM is an acronym for _______. Electrically Erasable

PROM

5. PROM is an acronym for _______. Programmable ROM


Important Semiconductor Memory Characteristics:

Non Volatile Electrically

Updatable

High

Density

EPROM

ROM

DRAM

EEPROM

SRAM +

Battery

FRAM

Flash

MRAM

Overview of Memory (Continued)


QUIZ

1. Both a ROM and EPROM are nonvolatile and have

high density but cannot be electrically updated.


2. The DRAM is a high density semiconductor memory

that __________ (can, cannot) be electrically updated.

can

3. The __________ (Flash, PROM) is a modern memory

that exhibits high density, is nonvolatile, and can be

updated electrically. Flash

4. SRAM with a battery backup (as in modern PCs) is

nonvolatile, and can be updated electrically. (True or

False)

True

5. FRAM and MRAM are both non-volatile RAMs

using newer technologies. (True or False) True


• Data can be “written” to RAM

• Stored data can be “read” at any time

• Volatile - cannot be used for permanent memory

• Access to any memory location (address) at any moment

Random-Access Memory (RAM)

• SRAM (Static RAM) - stores data in flip-flop-like cells.

Holds 0 or 1 as long as IC has power (volatile).

• DRAM (Dynamic RAM) - memory cells need refreshing

many times per second. Also volatile.

Characteristics of RAM:

Types of RAM:


QUIZ

1. Two types of RAM semiconductor memories are

the DRAM and __________. SRAM

2. The RAM is a __________ (non-volatile, volatile)

semiconductor memory.

volatile

3. Modern computers contain both SRAM and

DRAM types of semiconductor memories. (True

or False) True

4. Both SRAM and DRAM are types of read-only

semiconductor memories. (True or False) False

5. RAM semiconductor memory has exactly the

same characteristics as Flash memory because

they are non-volatile, can be updated electrically,

and have high density. (True or False) False


• Non-volatile - memory is not lost when

power is turned off

• Data is stored permanently

• Data stored in ROM can be “read” at

any time

• ROM cannot be reprogrammed

• High density

Read-Only Memory (ROM)

Characteristics of ROM:


QUIZ

1. ROM stands for __________. Read-Only Memory

2. ROM is a semiconductor

memory that can be updated

electrically and is volatile.

(True or False) False

3. ROM is a high density

semiconductor memory that

__________ (can, cannot) be

reprogrammed.

cannot

4. Data is stored permanently in

a ROM semiconductor

memory. (True or False) True


• Mask-Programmable ROM (usually simply called ROM)

• Field-Programmable ROM (FPROM)

• Erasable Programmable ROM (EPROM)

• Electrically Erasable PROM (EEPROM or E2PROM)

• Flash EEPROM

Programmable Read-Only Memory

(PROM)

Data can be programmed or “burned” into a PROM.

Types of PROM:


Mask Programmable ROM (ROM): It can only be programmed

once and is generally known as ROM.

Field PROM (F-ROM): The key difference from a

standard ROM is that the data is written into a ROM during

manufacture, while with a PROM the data is programmed into them

after manufacture. ROMs are used only for large production runs,

while PROMs are used for smaller production where the program

may have to be changed.

Erasable PROM (EPROM): It is a type of memory chip that

retains its data when its power supply is switched off. In other

words, it is non-volatile. It is an array of floating-gate

transistors individually programmed by an electronic device that

supplies higher voltages than those normally used in digital circuits.

Once programmed, an EPROM can be erased by exposing it to

strong ultraviolet light source (such as from a mercury-vapor light).


Electrical Erasable PROM: An EPROM usually must be

removed from the device for erasing and programming, whereas

EEPROMs can be programmed and erased in-circuit, by applying

special programming signals. Originally, EEPROMs were limited

to single byte operations which made them slower.

Flash Memory: Flash memory is an electronic non-

volatile computer storage medium that can be electrically erased

and reprogrammed. Where as EPROMs had to be completely

erased before being rewritten, Flash memory may be written and

read in blocks (or pages) which are generally much smaller than

the entire device.


QUIZ

1. PROM stands for __________. Programmable

Read-Only Memory

2. A mask-programmable ROM can only

be programmed once and is generally

known as a ROM. (True or False) True

3. An EEPROM is an electrically

erasable PROM that is non-volatile

and can be updated electrically.


4. A Flash memory is an electrically

erasable PROM that has high

density, is volatile, and cannot be

updated electrically. (True or False) False


• SRAM with battery backup

- Typically a long-life lithium battery

Nonvolatile Read/Write Memory

• NVSRAM (Non-Volatile Static RAM)

- Better access speed and overall life than

SRAM with battery backup

• Flash Memory

- Nonvolatile

- In-system rewritable (read/write)

- Highly reliable

- Low power consumption

- High density

• Nonvolatile memory - memory that can retain

stored information when power is turned off.


QUIZ

1. Memory that retains its stored information

even when power is turned off is referred to

as __________ (volatile, nonvolatile). nonvolatile

2. SRAM is a __________ (volatile, nonvolatile)

type of semiconductor memory.

volatile

3. SRAM with battery backup as used in

modern PCs is a _________ (volatile,

nonvolatile) type of semiconductor memory.

nonvolatile

4. Flash memory features high density, is

reliable, can be electrically updated and

is __________ (volatile, nonvolatile). nonvolatile


Other Nonvolatile RAM (Using newer technologies)

•FRAM (ferroelectric RAM)

-Nonvolatile RAM

-In-circuit programmable

-Good access speed

-Low density

-High cost

-Ferroelectric capacitor and MOS transistor memory cell

•MRAM (magnetoresistive RAM)

-Nonvolatile RAM

-In-circuit programmable

-Excellent access speed

-High density

-Nanotechnology used in fabrication


• DIP (Dual In-line Package)

• SIP (Single In-line Package)

• ZIP (Zig-zag In-line Package)

• SIMM (Single In-line Memory Module)

• DIMM (Dual-In-line Memory Module)

• RIMM (like DIMM by Rambus, Inc.)

• Memory card (like Flash memory card)

Common Methods of Packaging

Semiconductor Memory


Primary storage - computer’s internal storage

Secondary storage - external storage

Computer Bulk Storage Devices

• Mechanical Devices

- Punched paper card

- Punched or perforated paper tape

• Magnetic Devices

- Magnetic tape (sequential-access device)

- Magnetic drum

- Hard disk

- Floppy disk

Types of secondary storage devices:


Computer Storage Devices

•Optical Devices

- CD-ROM (Read-only)

- CD-R (recordable)

- CD-RW (rewritable)

- WORM (Write-once Read-many

- DVD (Digital versatile disc or digital video disc)

- Magneto-optical disc- part optical/part magnetic

• Semiconductor Devices

- Flash EEPROM semiconductor memory

Types of Secondary Storage Devices (cont’d.):


QUIZ

1. A 3.5 inch floppy disk is an example

of a __________ (primary, secondary)

storage device.

secondary

2. The SRAM in your PC is an example

of a __________ (primary, secondary)

storage device.

primary

3. The CD-R optical disc is __________

(recordable, rewritable). recordable

4. The CD-RW optical disc is _________

(recordable, rewritable). rewritable


Digital Potentiometer Digital potentiometer is an electronic device comparable to

a traditional potentiometer with resistance outputs variable

in discrete steps. The wiper position is stored in EEPROM

when the power is turned off. Digital input pulses control

the movement of the wiper. Also referred to as a solid-state

potentiometer or non-volatile (NV) digital potentiometer.

Res

ista

nce

(1

0kΩ

- 1

0 S

tep

s)

Control

Logic

EEPROM

INC

U / D

+5V Power ON

Sets

position of

wiper

stored in

EEPROM

6K ohms

H

L

LOW=Down

Negative pulse 1 5K ohm

50%

Negative pulse 2

4K ohm

40%

5K ohm

50%

HIGH=Up

Negative pulse 3 6K ohm

60%

Negative pulse 4


QUIZ

1. The electronic equivalent of a

potentiometer is called a solid-state

potentiometer or __________. Digital potentiometer

2. The digital potentiometer contains a

__________ (EEPROM, ROM)

section to store the wiper position on

power down and recall the wiper

position on power up.

EEPROM

3. A single negative pulse will cause the

wiper of a digital potentiometer to

move one discrete step up or down

depending on the condition of the

U/D’ control input. (True or False) True


REVIEW

• Overview of Memory

• Random Access Memory (RAM)

• Read Only Memory (ROM)

• Programmable ROM (PROM)

• Nonvolatile Read/Write Memory

• Memory Packaging

• Computer Bulk Storage Devices

• Digital Potentiometer with NV EEPROM

Documents

Principles of Digital Electronics€¦ · Principles of Digital Electronics Chapter 06 Memories ... semiconductor memories. (True or False) True 3. Generally, if a semiconductor memory