Flash and EEPROM.

What is the difference between Flash and EEPROM?

Datasheets of the microcontroller, specify Flash endurance of 10k W/E cycles while EEPROMS 100K W/E Cycles. Also Wikipedia claims Flash to be cheaper than EEPROM and also that the reason for shorter endurance is that Flash is writen and erased in blocks while EEPROM can be edited byte by byte. So Flash has more wearing across it's life.

Why the cost difference?

Thank you.

lord loh. said:

What is the difference between Flash and EEPROM?

Datasheets of the microcontroller, specify Flash endurance of 10k W/E cycles while EEPROMS 100K W/E Cycles. Also Wikipedia claims Flash to be cheaper than EEPROM and also that the reason for shorter endurance is that Flash is writen and erased in blocks while EEPROM can be edited byte by byte. So Flash has more wearing across it's life.

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FLASH is often used when the technology is really EEPROM, as far as I'm aware Atmel were the first to use this advertising technique (claiming their earlier AVR processors were FLASH, when they were actually EEPROM). At that time MicroChip were correctly calling their PIC processors EEPROM, but it didn't take long for the MicroChip marketing department to follow suit - and PIC EEPROM processors became renamed FLASH over night. Of the new MicroChip devices, some are still EEPROM based, and some are FLASH, but all are classed as FLASH (presumably Atmel may well do the same?, but neither will tell you this!).

So FLASH is generally treated as an advertising 'buzz word' and not a specific technology at all.

In practice it really makes no difference, unless you're writing a programmer for them!.

Wikipedia claims that Flash is cheaper. Also why should EEPROM be cheaper? Or is there an anomaly in Wikipedia?

Just an after thought....

Does any type of a memory have an internal battery that takes the IC in low power mode to retain data content while making it inoperatable? I vaguely remember reading about it in some magazine an year ago....

lord loh. said:

Wikipedia claims that Flash is cheaper. Also why should EEPROM be cheaper? Or is there an anomaly in Wikipedia?

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No idea?, I don't make or design chips.

Possibly true 'FLASH' uses less silicon?, or a cheaper technique?.

lord loh. said:

Does any type of a memory have an internal battery that takes the IC in low power mode to retain data content while making it inoperatable? I vaguely remember reading about it in some magazine an year ago....

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Don't know about a year ago? - but historically (25 years ago?) there have been CMOS static RAM's that had batteries to retain memory when the power was disconnected. But generally it was more common to have a battery on board feeding the memory (like the CMOS RAM in a PC).

The difference between FLASH and EEPROM is a bit more than marketing bumpf. Flash cells are characterized by the presence of 2 gates. The method of placing and extracting electrons from the floating gates are different than in EEPROM. These are things of interest to chip designers. To the rest of us it hardly matters.

The one thing which is certain about the business besides Moore's Law is that any statement made about relative pricing will be moot in the "futura prossimo" (next future), as out Italian friends would say.

Flash should be smaller, hence less silicon per chip, more chips per wafer, so forth. Or from another perspective, what's the largest capacity EEPROM chip you've seen vs the biggest Flash chip? I think that even the SPI serial Flash chips available can cram 1 MByte in a 8 pin SOIC.

I think Maxim still sells some parts with integrated (molded into the package) batteries. Most of these are beefed up RTC parts.

hjames said:

Flash should be smaller, hence less silicon per chip, more chips per wafer, so forth. Or from another perspective, what's the largest capacity EEPROM chip you've seen vs the biggest Flash chip? I think that even the SPI serial Flash chips available can cram 1 MByte in a 8 pin SOIC.

I think Maxim still sells some parts with integrated (molded into the package) batteries. Most of these are beefed up RTC parts.

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NAND Flash has higher density. But NOR flash seems to provide random access. While NAND flash is sequentially accessed.