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Flash Memory and Micro SD Card
Presented by:
Krishna Goyal
(200601195)
Anirudh Tripathi (200601141)
OUTLINE
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Memory
Volatile and Nonvolatile memory
EPROM and EEPROM memory
Flash memory
NAND and NOR Flash memory
Flash Memory operations
Advantage and Disadvantage of Embedded Over Stand Alone
Flash Memory
• Micro SD card
• Summary
• References
Memory
• The terms “storage” or “memory” refer to the parts
of a digital computer that retain physical state (data)
for some interval of time, possibly even after
electrical power to the computer is turned off.
• A computer system's memory is crucial to its
operation; without memory, a computer could not
read programs or retain data. Memory stores data
electronically in memory cells contained in chips. It is
usually measured in kilobytes, megabytes, or
gigabytes.
• Memory is classified into volatile and non-volatile
memory.
Memory Classification
VOLATILE
NON-VOLATILE
SRAM
ROM
PROM
DRAM
EPROM
EEPROM
NVRAM
Flash Memory
Floppy Disk
MRAM
Hard Disk
Magnetic Devices
Volatile Memory
• The most widely used form of primary storage today
is a volatile form of random access memory, meaning
that when the computer is shut down, anything
contained in random access memory (RAM) is lost.
• DRAM used for main memory
• SRAM used for cache
Non-Volatile memory
• EEPROM, EPROM, FeRAM, FLASH, NVSRAM and
ROM are different types of non-volatile memory.
• The main differences are in the memories relative
cost per bit and the flexibility to accommodate code
changes.
• nonvolatile memory, NVM or non-volatile storage, is
computer memory that can retain the stored
information even when not powered.
EPROM
• Erasable Programmable Read Only Memory also
known as UV-EPROM is a form of non-volatile
memory. It is programmed electrically at high
voltage using a charge that is injected into the
floating gate. Data is erased by exposing the EPROM
to UV light. The memory chip may then be reprogrammed with new data.
• EPROMs are expensive because of the special quartz
window packaging required for erasing
capability. EPROMs are quickly being replaced by
FLASH memory devices.
EEPROM
• (Electrically Erasable Programmable ROM) A
rewritable memory chip that holds its content
without power. EEPROMs have a lifespan of between
10K and 100K write cycles, which is considerably
greater than the EPROMs that came before them.
• Unlike E-PROMs, which have to be placed under UV
light for erasure, EEPROMs are erased in place. They
use a floating gate to hold a charge like an E-PROM
and have a second transistor for erasure.
Flash Memory
• Flash memory is a programmable, read-only,
nonvolatile memory similar to EPROM and EEPROM.
Although flash memory is a derivative of EPROM and
EEPROM.
• EEPROM is automatically erased before a WRITE on a
byte basis. Flash is either erased in blocks or the
entire chip at once.
• Flash memory is made of either NOR or NAND gates.
Flash Memory
• Flash memory is used in memory card and flash
drives to transfer data.
• They are removable and re-writable and are much
shorter than floppy disk and hold more information.
• Flash memory is used in devices as cameras , mobile
phones and video games.
• Examples:-BIOS chip, compact flash, Smart media,
Memory stick, Memory card.
Flash Memory Cell
Memory Architecture Diagram
USB Flash Drive
NAND and NOR Flash Memory
• NOR flash supports random access and is used for instruction
storage and execution known as "execute in place" (XIP). With
a lifespan of about 100K write cycles, erasing and writing take
several seconds, but reading is fast.
• NAND flash, developed by Toshiba, reads and writes
sequential, disk sector-sized blocks of 512 bytes, but must be
erased in blocks from 16KB to 128KB. Less expensive than
NOR, NAND flash can be rewritten up to a million times.
Writing and erasing NAND flash is also faster than NOR.
Flash Memory Operation
• Flash memory stores information in an array of
floating gate transistors, called "cells", each of which
traditionally stores one bit of Information
• Newer flash memory devices, sometimes referred to
as multi-level cell devices, can store more than 1 bit
per cell, by using more than two levels of electrical
charge, placed on the floating gate of a cell
Flash Memory Operation
• Most modern NOR flash memory components are
divided into erase segments, usually called either
blocks or sectors.
• All of the memory cells in a block must be erased at
the same time.
• Programming in NOR , generally performed one byte
or word at a time.
NAND vs. NOR
• NAND's advantages are fast write (program) and
erase operations, while NOR's advantages are
random access and byte write capability
• NOR's random access ability allows for execute in
place (XiP) capability, which is often a requirement in
embedded applications
NAND/NOR Characteristics
NAND vs. NOR
• The disadvantages for NAND are slow random access,
while NOR is, its slow write and erase performance.
• The real benefits for NAND are faster program and
erase times, as NAND provides over 5 Mbytes/s of
sustained write performance.
• The block erase times are 2 ms for NAND and 700 ms
for NOR.
• Clearly, NAND has several significant positive
attributes.
• However, it's not well-suited for direct random access.
Advantage of Embedded Over
Stand-Alone Flash Memory
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Higher System Speed
Lower Power
Higher Reliability
Improved Security
System-On-Chip(SOC) Capability
Lower System Cost
Disadvantage of Embedded Over
Stand-Alone Flash Memory
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Single Source
Increased Process Complexity
Increased Test Cost
Density Limitation
Introduction to Micro SD Card
• MicroSD card is the memory card that is small and
thin with SDMI(Secure Digital Music Initiative).
• It is Flash based memory card designed to meet
security, capacity, performance and environment
requirements inherent to used in emerging audio
and video electronic devices.
• One of the great advantages of the Micro SD Cards is
that they are backward compatible with many
electronic devices that use standard SD memory
cards.
Micro SD Card Interface
Description
Features
• Performance
• Data Transfer Rate Read up to 23 MB/sec
(Max)
• Data Transfer Rate Write up to 20 MB/sec
(Max)
Features
• Add microSD card adapter can be use in SD
card socket.
• Support CPRM code.
• No external programming voltage required.
• SD card protocol compatible.
• Correction memory field errors.
• Easy handling for end user.
SD/SPI Bus Comparison
microSD card using SD bus
• Six wire communication
channel( clock, command, 4
data lines)
• Error protected data
transfer
• Single or multiple block
oriented data transfer.
microSD card using SPI bus
• Three wire serial data bus
( clock, dataIn, dataOut)+
card specific CS signal(hard
wired card selection)
• Optinal non protected data
transfer mode available.
• Single or multiple block
oriented data transfer.
MicroSD card pinpout SD mode
MicroSD card pin out SPI mode
Product Specification
Product Specification
Product Specification
Summary
• Flash technology is constantly changing, providing faster
program and erase cycles, a bigger number of guaranteed
erase and re-program cycles and longer data retention. Flash
technology put on-chip with microcontrollers has now
reached the point, where the in-application usability greatly
improved.
• In the past, storing of configuration data that stays available
after a power-down and power-up cycle required an
additional EEPROM or other storage device. Today, this
functionality can be provided by on-chip Flash, further
decreasing the parts count of embedded applications: an
additional external EEPROM or SRAM might not be required
anymore.
References
• http://www.puremobile.com/flash-memorycards.asp
• http://www.esacademy.com/faq/docs/flash/index.ht
m
• http://electronics.howstuffworks.com/flashmemory.htm
• http://en.wikipedia.org/wiki/Flash_memory
• http://www.dharmanitech.com
References
• Paolo Cappelletti, Carla Golla, Piero Olivo, Enrico
Zanoni “Flash Memories”, Kluwer Academic
Publishers.
• Joe E. Brewer and Manzur Gill “Nonvolatile Memory
Technologies with Emphasis on Flash ”, Wiley
Interscience