Amit Weissenstern JTAG course 2009 Hebrew University Jerusalem Israel Flash memories Amit Weissenstern JTAG course 2009 Hebrew University Jerusalem Israel

Usage of Flash memories Your computer's BIOS chip Flash memory cards (MMC, CF, SD, etc…) USB storage devices (flash drives) PCMCIA memory cards Memory cards for video game consoles Many more… BIOS מערכת קלט/פלט בסיסית, התכנה הצרובה בזיכרון המחשב ומופעלת מרגע אתחולו PCMCIA Type I and Type II memory cards (used as solid-state disks in laptops) Flash memory cards (MMC, CF, SD) often used in cameras Multi media card, compact flash, Secure digital flash memory offers fast read access times (although not as fast as volatile DRAM memory used for main memory in PCs) and better kinetic shock resistance than hard disks (are able to withstand intense pressure, extremes of temperature, and even immersion in water) . These characteristics explain the popularity of flash memory in portable devices

Background Toshiba presented the NOR flash (1984) Toshiba announced NAND flash (1987) Intel introduced the first commercial NOR type flash chip (1988) Global NAND flash memory annual revenue is $15.2 billion (2008) Toshiba presented the invention at the IEEE 1984 International Electron Devices Meeting (IEDM) held in San Francisco, California. Its name comes from the fact that flash memory can be erased very quickly (like the speed of the flash on a camera

Types of memories Memories Volatile Non Volatile SRAM PROM Flash ROM DRAM EEPROM EPROM

Flash - Advantages Non-volatile Electrically erased and reprogrammed Solid state Can be accessed (read) at high speed. Single/Multi Level הוא שבב המאפשר כתיבה ומחיקה חוזרת על גבי השבב שמאחסן את המידע לאורך זמן ללא תלות במקור חשמל כלשהו, המחובר לשבב. זאת, בניגוד לזיכרון נדיף. - שבב זיכרון הֶבְזֵק (Flash memory) (Electrically Erasable Programmable Read-Only Memory) Specific type of EEPROM Erased and programmed in large blocks

Flash - Disadvantages Limited life of about 100,000 to 1,000,000 erase and write operations. Erasing is a block-level function. Longer time periods are required for erasing and writing. Access Time (μs): sufficient for many applications

Bit level structure Clear flash = All bits are set to one. Writing to flash is a two-step process: The memory must first be erased as a block (all ones). A write operation only writes a zero into a memory cell.

Flash file system Use of specifically designed flash file systems/controller to perform wear- leveling and error correction. Spread writes over the media. Defragmentation. Update storage method. When the flash store is to be updated, the file system will write a new copy of the changed data over to a fresh block, remap the file pointers, then erase the old block later when it has time.

NAND vs. NOR NOR Enables direct access to each memory cell. Fast random access, but slower write speed. Uses silicon less efficiently, resulting in higher cost per bit. NAND Enables sequential access to memory cells. Faster write and erase speed. Uses silicon more efficiently, resulting in lower cost per bit. NAND has far outpaced NOR, due to faster write and erase performance and lower cost.

Building blocks

Write – NOR flash

Read – NOR flash

Erase – NOR flash

Flash memory and Testability Testability for Flash memory: Structural Tests Functional tests Flash memory & JTAG technology: Use of flash in ‘On-Board Programming’ ( On-Board Programming ) יישומי צריבות תוך-מעגל עם טכנולוגיית ג'טאג, זוכים להתעניינות גוברת בימים אלה. תהליכי צריבות תוך-מעגל מתייחסים בדרך כלל לצריבה (הן כתיבה והן קריאה) של רכיבי זיכרון פלאש טכנולוגיה זו היא ג'טאג דרך רכיבי המגמה השלטת בימים אלה Structural Tests כדאי להכין את השבב לבדיקתיות. במיוחד לאור הגדלים ההולכים וקטנים Functional tests חשיבות מכרעת בכל הקשור למהירויות קריאה, כתיבה ומחיקה

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