'A simple question .....'
Ricardo Ponte G
Well, I«m pretty new in the PIC«s world and I was reading some datas
and I read a term:
"PICmicro FLASH device" so, what«s the mean of " FLASH device "
What«s the mean of "PICmicro FLASH devices ???
What«s FLASH ???
If somebody can help me, I«ll apreciate it very much...
On Tue, May 19, 1998 at 01:15:18AM -0400, Ricardo Ponte G wrote:
> "PICmicro FLASH device" so, what«s the mean of " FLASH device "
It's a device that indecently exposes itself :-)
Seriously, FLASH is a fancy term for a kind of electrically-erasable
programmable read-only memory (EEPROM). The exact difference between
FLASH and regular EEPROM depends on which marketing person you talk to,
but basically FLASH is always bulk-erased, whereas (some) EEPROM can be byte
I think the original term came from the fact that it can be erased in a flash.
Clyde Smith-Stubbs | HI-TECH Software
Email: htsoft.com | Phone Fax clyde
WWW: http://www.htsoft.com/ | USA: (408) 490 2885 (408) 490 2885
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HI-TECH C: compiling the real world.
At 05:19 PM 19/05/98 +1000, you wrote:
Clyde is right, however the difference can be expanded somewhat more. A
FLASH device must have all the bits set to 1 i.e. FF as it can only clear
the bits in the macrocell i.e. wrtie a 0 to it (During programme), whereas
an EEPROM can change the state of any bit. Also the FLASH device has 4 gates
per memory cell, whereas; an EEPROM has 6.
Dennis Plunkett: Embedded Hardware, Software design
NEC Australia DRMASS
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On Wed, 20 May 1998,
To: pic microcontroller discussion list <MITVMA.MIT.EDU> PICLIST
On Wed, 20 May 1998, Samir OMAR wrote:
> Date: Wed, 20 May 1998 09:44:45 +1000 (EST)
> From: Samir OMAR <cse.unsw.EDU.AU> omar
> To: pic microcontroller discussion list <MITVMA.MIT.EDU> PICLIST
> Cc: cse.unsw.edu.auomar
> Subject: Re: A simple question .....
|Dennis Plunkett <RDD.NECA.NEC.COM.AU> wrote: dennis
> Also the FLASH device has 4 gates
> per memory cell, whereas; an EEPROM has 6.
Actually, no. Maybe you're thinking of SRAM cells; low power CMOS SRAM uses
six transistor cells, and higher density (but higher power) cells use
four transistor cells.
EPROM, EEPROM, and Flash all ususally use one transistor per cell, although
it is an unusual transistor with a second "floating" gate. For very
high speed memory, Sometimes a second transistor is added, because the same
characteristics that make a good storage transistor also make a relatively
In the past EEPROM cells sometimes had two separate floating gate
transistors for storing ones and zeros, and read the bits using differential
sensing. In such devices, the erased (or unprogrammed) state was
indeterminate. This was relatively common in the old MNOS (*) EEPROMs.
However, I don't think this technique is much used any more.
Maybe someone from Microchip would care to comment on how their Flash
(*) Yes, I really meant MNOS. Not NMOS.
From: Clyde Smith-Stubbs <HTSOFT.COM> clyde
To: MITVMA.MIT.EDU < PICLISTMITVMA.MIT.EDU> PICLIST
Date: Tuesday, May 19, 1998 4:39 AM
Subject: Re: A simple question .....
>Seriously, FLASH is a fancy term for a kind of electrically-erasable
>programmable read-only memory (EEPROM). The exact difference between
>FLASH and regular EEPROM depends on which marketing person you talk to,
>but basically FLASH is always bulk-erased, whereas (some) EEPROM can be
>I think the original term came from the fact that it can be erased in a
In a book "What a Great Idea" Charles "Chic" Thompson describes his
interview with Yoshiro NakaMats (inventor of CD, floppy, digital watch
etc. - more than 2,300 patents all together):
C.T.: I've read that you come up with a patentable idea every day. Have you
come up with one today?
Y.N.: No, let's invent a product together. What would you buy if it were
C.T.: I'd buy a recording device, about the size of a credit card, that
could fit in my shirt pocket. Every time I had a flash of an idea, I could
just record it. It would be voice activated, with a very large memory, and
have a voice activated filing system for idea management.
Y.N.: What would you call it?
C.T.: I'd call it "Flash" - because it would just be flashes of ideas, which
you could then download onto a computer system.
Y.N.: Very good. This will be our first product together, so when I get
home, I'll turn it over to my research department.
I am not sure, but could this be an origin of a term "Flash" memory?
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