27c256b an eprom or an eeprom?
Craig Nelson
rewriteable..
I've only got two of them and may only get one shot at each.. I can't
find any data sheets on it.
If you can point me in the proper direction, I'd sure appreciate it!
thanks
Craig
LdaVinci
wrote:
Hi Craig!
The complete part number is M27C256B-(dash) followed by:
2 numbers, defining one of 10 speeds, from 45 ns (45) to 250 ns (25)
+
a blank or an X, indicating Vcc tolerance... blank=10%, X= 5%
+
one of 4 alpha characters, for the type of package: F, B, C or N
+
one of 3 numbers, defining max. oper. temperature: 1= 0 to 70 deg. C,
3= -40 to +125 deg. C, or 6= 140 to +85 deg. C
+
one of 2 alpha characters to indicate supplied option: X for
"additional burn-in" or TR for tape & reel packing
Depending on the "type of package" (see above) the chip is either an
UV erasable EPROM or a PROM (program once device) also called one time
programmable or OTP.
The usual transparent (clear) plastic window on the top face of the
chip will denote an UV erasable EPROM. Absence of such window will
tell you it's an OTP.
The pinout for the UV erasable type is as follows:
1 - Vpp (programming or erasing voltage = 12.75 Volt, or = Vcc for all
other modes)
2 - A12
3 to 10 - A7 to A0 respectively
11 to 13 - Q0 to Q2 respect.
14 - Vss (ground level)
15 to 19 - Q3 to Q7, respect.
20 - E (cxhip enable, TTL levels, active on descending slope)
21 - A10
22 - G (output enable, TTL levels, active on descending slope)
23 - A11
24 - A9
25 - A8
26 - A13
27 - A14
29 - Vcc (normal read voltage = 6.25 +/- 0.25 Volt)
Hope this info is sufficient for your needs. Enjoy.
Cheers
daVinci
NoBodyInParticular
Not to be picky, the data you supplied is all good
information, but the window is quartz glass, plastic stops
UV light in its tracks and would never allow the chip to be
erased.
Bruce Lane
cr...@reversion.ca says...
> Just wondering if anyone out there knows if the 27C256B eprom is
> rewriteable..
Only if it's exposed to the appropriate wavelength of UV light
between writings. ;-)
In short, it's a UV EPROM.
> I've only got two of them and may only get one shot at each.. I can't
> find any data sheets on it.
You don't have a UV eraser?
--
Bruce Lane, Owner and Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
Amateur Radio: KC7GR (Formerly WD6EOS) since 12-77.
kyrrin (a/t) bluefeathertech dot-com (Reassemble to use)
"I'll get a life when someone demonstrates to me it would be superior to
what I have now..." (Taki Kogoma)
Michael A. Terrell
>
>
> The complete part number is M27C256B-(dash) followed by:
Wrong!
The prefix part of the part number would depend on who made it.
256Kb EPROMs were jellybean parts made by dozens of companies, with
different prefix to show who made it, and suffix to indicate the speed.
--
Michael A. Terrell
Central Florida
Richard Steven Walz
Craig Nelson <cr...@reversion.ca> wrote:
>Just wondering if anyone out there knows if the 27C256B eprom is
>rewriteable..
>I've only got two of them and may only get one shot at each.. I can't
>find any data sheets on it.
What are you talking about? That's an EPROM, of course it is rewritable,
but not without being ERASED first IF it is the WINDOWED version. If it
is NOT windowed then forget it, it can be written precisely ONCE ONLY.
The same die is in both windowed and non-windowed, but you need the window
and a UV eraser to erase it. If you want to write to unused parts of it
you may be able to do that.
What did you MEAN that you "may only get one shot at each"???? You cannot
rewrite it without erasing unless you are burning to 0 bits which are now
1's.
-Steve
Craig Nelson
27C256 (non-windowed version) is an EPROM (write once) not an EEPROM
(Rewriteable).
Interestingly, it seems the 28C256 (and any other with a 28 prefix) is
an EEPROM.
I was concerned about it because I dont have a UV eraser.. I'm finally
getting
into all of this and have only purchased the programmer thus far..
Thanks to all who replied!
Craig
rst...@deeptht.armory.com (Richard Steven Walz) wrote in message news:<3e376ea4$0$79559$8ee...@newsreader.tycho.net>...
Richard Steven Walz
Craig Nelson <cr...@reversion.ca> wrote:
>What I meant by "only one shot" is precisely what I thought.. the
>27C256 (non-windowed version) is an EPROM (write once) not an EEPROM
>(Rewriteable).
You're a little confused, an EPROM *IS* rewritable if it has a window
in it and if you erase it with a UV germicidal lamp of 253.7 nanometers.
It is ONLY OTP (one-time-programmable) IF it HAS NO window! Both
are EPROMs and BOTH have the SAME EXACT DIE inside. In other words,
it is NOT EPROM that makes it OTP, but the window! If you drilled
a hole in it down to the EPROM die, you COULD erase it!
-Steve
--
-Steve Walz rst...@armory.com ftp://ftp.armory.com/pub/user/rstevew
Electronics Site!! 1000's of Files and Dirs!! With Schematics Galore!!
http://www.armory.com/~rstevew or http://www.armory.com/~rstevew/Public
Sylvan Butler
> What I meant by "only one shot" is precisely what I thought.. the
> 27C256 (non-windowed version) is an EPROM (write once) not an EEPROM
> (Rewriteable).
No. EPROM == Erasable Programable Read Only Memory. It is
understood that means "Erasable via ultraviolet", "Programmable via
some electrical method" but normal operation is "Read Only" (a
memory write won't program it). Because ultraviolet exposure is
required to erase it, if there is no window in the package, the chip
cannot be erased. Electrically it is still an EPROM, so the part
number is not changed in substance (usually there will be a
different suffix for windowed vs non-windowed (cheaper) parts).
An EEPROM == Electrically Erasable Programmable Read Only Memory.
The progenitor of flash memory, it can be erased electrically but
the process is significantly slower and/or more cumbersome than a
typical memory write cycle, so erasure and programming is not a
typical mode of operation. I've never seen an EEPROM with a window.
Why would they put an expensive window into the package of an
electrically erasable part?
sdb
--
| Sylvan Butler | Not speaking for Hewlett-Packard | sbutler-boi.hp.com |
| Watch out for my e-mail address. Thank UCE. >>>> change ^ to @ <<<< |
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own good will torment us without end, for they do so with the approval
of their consciences. -- C. S. Lewis
Peter Bennett
wrote:
>What I meant by "only one shot" is precisely what I thought.. the
>27C256 (non-windowed version) is an EPROM (write once) not an EEPROM
>(Rewriteable).
>
>Interestingly, it seems the 28C256 (and any other with a 28 prefix) is
>an EEPROM.
The 27xxx series parts are UV-erasable if they are in a windowed
package. Some manufaturers may also put them in a cheap windowless
plastic package, and call them "OTP" (one-time programmable), because
they can't be exposed to UV light.
The 28xxx parts are electrically erasable and reprogrammable, and are
normally in plastic packages.
--
Peter Bennett VE7CEI
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