Principles of Digital Electronics€¦ · Principles of Digital Electronics Chapter 06 Memories ......
Transcript of Principles of Digital Electronics€¦ · Principles of Digital Electronics Chapter 06 Memories ......
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
Principles of Digital
Electronics
Chapter 06
Memories
Mr. Nikhil Satpute
©2008 The McGraw-Hill Companies, Inc. All rights reserved.
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
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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
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• 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:
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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.
(True or False) True
4. A semiconductor memory that can be updated
is referred to as a(n) __________ (read-only,
read/write) memory.
read/write
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• 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:
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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
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Important Semiconductor Memory Characteristics:
Non Volatile Electrically
Updatable
High
Density
EPROM
ROM
DRAM
EEPROM
SRAM +
Battery
FRAM
Flash
MRAM
Overview of Memory (Continued)
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QUIZ
1. Both a ROM and EPROM are nonvolatile and have
high density but cannot be electrically updated.
(True or False) True
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
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• 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:
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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
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• 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:
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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
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• 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:
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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).
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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.
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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.
(True or False) True
4. A Flash memory is an electrically
erasable PROM that has high
density, is volatile, and cannot be
updated electrically. (True or False) False
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• 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.
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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
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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
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• 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
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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:
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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.):
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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
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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
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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