Flash Memory • FRAM (Ferroelectric RAM) • MRAM (Magnetoresistive RAM) See Future Slides for Characteristics of Each Category of Memory

Home , EEPROM, EPROM, Ferroelectric RAM, Flash memory, Magnetoresistive RAM, Optical disc

Principles of Digital Electronics

Mr. Nikhil Satpute

Chapter 06 Memories

• 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

Memory

RAM ROM (Read Sequential (Random Only Memories Access Memory) Memory)

SRAM DRAM Flash Masked ROM (Static (Dynamic PROM EPROM EEPROM EEPROM RAM) RAM)

Three Important Characteristics of Semiconductor Memory: • 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

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 read/write) memory.

• 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) See future slides for characteristics of each category of memory. ©2008 The McGraw-Hill Companies, Inc. All rights reserved. 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:

High Density

EPROM DRAM ROM Flash MRAM

Non Volatile Electrically EEPROM Updatable SRAM + Battery FRAM

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 Flash updated electrically. 4. SRAM with a battery backup (as in modern PCs) is nonvolatile, and can be updated electrically. (True or True False) 5. FRAM and MRAM are both non-volatile RAMs using newer technologies. (True or False) True

©2008 The McGraw-Hill Companies, Inc. All rights reserved. Random-Access Memory (RAM) Characteristics of RAM: • 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

Types of 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.

1. Two types of RAM semiconductor memories are the DRAM and ______. SRAM 2. The RAM is a ______(non-volatile, volatile) volatile semiconductor memory. 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 ©2008 The McGraw-Hill Companies, Inc. All rights reserved. Read-Only Memory (ROM)

Characteristics of ROM: • 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

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 cannot reprogrammed. 4. Data is stored permanently in a ROM semiconductor memory. (True or False) True ©2008 The McGraw-Hill Companies, Inc. All rights reserved. Programmable Read-Only Memory (PROM)

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

Types of PROM: • Mask-Programmable ROM (usually simply called ROM)

• Field-Programmable ROM (FPROM)

• Erasable Programmable ROM (EPROM)

• Electrically Erasable PROM (EEPROM or E2PROM)

• Flash EEPROM

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 nonvolatile 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.

Programmable 1. PROM stands for ______. 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 ©2008 The McGraw-Hill Companies, Inc. All rights reserved. Nonvolatile Read/Write Memory • Nonvolatile memory - memory that can retain stored information when power is turned off. • SRAM with battery backup - Typically a long-life lithium battery • Flash Memory - Nonvolatile - In-system rewritable (read/write) - Highly reliable - Low power consumption - High density • NVSRAM (Non-Volatile Static RAM) - Better access speed and overall life than SRAM with battery backup ©2008 The McGraw-Hill Companies, Inc. All rights reserved. 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) volatile type of semiconductor memory.

3. SRAM with battery backup as used in modern PCs is a ______(volatile, nonvolatile nonvolatile) type of semiconductor memory. 4. Flash memory features high density, is reliable, can be electrically updated and is ______(volatile, nonvolatile). nonvolatile

•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

©2008 The McGraw-Hill Companies, Inc. All rights reserved. Common Methods of Packaging Semiconductor Memory • 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)

Primary storage - computer’s internal storage Secondary storage - external storage

Types of secondary 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

•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

1. A 3.5 inch floppy disk is an example of a ______(primary, secondary) secondary storage device. 2. The SRAM in your PC is an example of a ______(primary, secondary) primary storage device. 3. The CD-R optical disc is ______recordable (recordable, rewritable).

4. The CD-RW optical disc is ______rewritable (recordable, rewritable).

©2008 The McGraw-Hill Companies, Inc. All rights reserved. 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.

+5V Power ON

H U / D

LOW=DownHIGH=Up Control Sets

10 Steps) 10

- position of Ω Negative pulse 2341 Logic wiper 5K6K ohm INC 4K ohm stored in 50%60% 40% EEPROM EEPROM 6K ohms Resistance (10k Resistance L

1. The electronic equivalent of a potentiometer is called a solid-state potentiometer or ______. Digital potentiometer 2. The digital potentiometer contains a ______(EEPROM, ROM) EEPROM section to store the wiper position on power down and recall the wiper position on power up. 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 ©2008 The McGraw-Hill Companies, Inc. All rights reserved. REVIEW