Looking for 27C64 or 27C256 PROM

[Jorden Verwer]

Hello all,

I'm currently using a 8051 microcontroller system with an external
27C64 EPROM chip. However, I want to be able to ensure that the system
will remain functional for years to come, and EPROMs only last for
about 10 years. Therefore, I'd like to replace the EPROM chip with a
fuse-based PROM chip (not OTP EPROM). Does anyone know where I can
find one? I need only one such chip. I also don't have a programmer
for this kind of chip, so if anyone knows how I could build one or if
anyone wants to program a PROM chip for me, I'd be very grateful. I do
have access to an EPROM programmer but I don't think it would suffice.
If no 27C64-like PROM chips can be found anymore, a 27C256-like PROM
would do just as well.

Thanks in advance,

Jorden Verwer

 

[James Beck]

Hello all,

I'm currently using a 8051 microcontroller system with an external
27C64 EPROM chip. However, I want to be able to ensure that the system
will remain functional for years to come, and EPROMs only last for
about 10 years. Therefore, I'd like to replace the EPROM chip with a
fuse-based PROM chip (not OTP EPROM). Does anyone know where I can
find one? I need only one such chip. I also don't have a programmer
for this kind of chip, so if anyone knows how I could build one or if
anyone wants to program a PROM chip for me, I'd be very grateful. I do
have access to an EPROM programmer but I don't think it would suffice.
If no 27C64-like PROM chips can be found anymore, a 27C256-like PROM
would do just as well.

Thanks in advance,

Jorden Verwer

I don't know of ANY fuse PROMs with those densities.
We have several products that have been running for 20+ years with no
problems with the EEPROMs failing. I think using the right algorithm
for the part adds greatly to the reliability. Fuse PROMs are also not
without their problems. Metal migration can cause fuses that were blown
to "unblow" themselves.

Jim

 

[William P.N. Smith]

I'm currently using a 8051 microcontroller system with an external
27C64 EPROM chip. However, I want to be able to ensure that the system
will remain functional for years to come, and EPROMs only last for
about 10 years.

Dunno for sure about fuse PROMs, but programming algorythm may make a
significant difference in lifetime, as Jim Beck mentions. Instead of
using one of the 'fast' algorythms that hits a cell till it barely
changes, then programs the entire chip at some multiple of that time,
do the full (50ms?) burn on each location. Takes a lot longer, but
you'll get more electrons {in,out} of the floating gate, and they'll
last longer.

I suppose you could do multiple EPROMS with voting, or build a
programmer into the circuit and allow the CPU to refresh it's own
EPROM once a year, but that probably adds enough complexity to reduce
the overall circuit reliability...

 

[Peter Bennett]

Hello all,

I'm currently using a 8051 microcontroller system with an external
27C64 EPROM chip. However, I want to be able to ensure that the system
will remain functional for years to come, and EPROMs only last for
about 10 years. Therefore, I'd like to replace the EPROM chip with a
fuse-based PROM chip (not OTP EPROM). Does anyone know where I can
find one? I need only one such chip. I also don't have a programmer
for this kind of chip, so if anyone knows how I could build one or if
anyone wants to program a PROM chip for me, I'd be very grateful. I do
have access to an EPROM programmer but I don't think it would suffice.
If no 27C64-like PROM chips can be found anymore, a 27C256-like PROM
would do just as well.

We've had UVPROM-based systems in use here for over 20 years, so I
don't think think you need to worry about the EPROMs forgetting.

Fuse PROMs were only made in fairly small sizes, as far as I recall -
I don't think you'll find any as large as a 2764 (and it is very hard
to find the small oned now.)

 

[Jorden Verwer]

I don't know of ANY fuse PROMs with those densities.
We have several products that have been running for 20+ years with no
problems with the EEPROMs failing. I think using the right algorithm
for the part adds greatly to the reliability. Fuse PROMs are also not
without their problems. Metal migration can cause fuses that were blown
to "unblow" themselves.

Hmm... I guess only hardwired ROM chips are truly durable then. Pity.

Dunno for sure about fuse PROMs, but programming algorythm may make a
significant difference in lifetime, as Jim Beck mentions. Instead of
using one of the 'fast' algorythms that hits a cell till it barely
changes, then programs the entire chip at some multiple of that time,
do the full (50ms?) burn on each location. Takes a lot longer, but
you'll get more electrons {in,out} of the floating gate, and they'll
last longer.

Okay, I'll use the slowest algorithm then. Would it help to program
the chip several times in succession? Or would that be damaging
instead?

One more thing (since it looks like I'm stuck with an EPROM): what is
the best material to cover the window with, in view of durability?

Thanks for your help,

Jorden

 

[Mark (UK)]

Hiya!

The largest BiPolar PROM that I have reference for is the 82S641 which
is an 8192x8 (same as 2764), but in a 24 pin package, so not directly
compatible.

The most secure way is to store an image of the data in the rom at
several locations, including multiple copies on CDR, and on a ZIP file
on the internet.

Yours, MArk.

 

[dont know]

Hello all,

I'm currently using a 8051 microcontroller system with an external
27C64 EPROM chip. However, I want to be able to ensure that the system
will remain functional for years to come, and EPROMs only last for
about 10 years. Therefore, I'd like to replace the EPROM chip with a
fuse-based PROM chip (not OTP EPROM). Does anyone know where I can
find one? I need only one such chip. I also don't have a programmer
for this kind of chip, so if anyone knows how I could build one or if
anyone wants to program a PROM chip for me, I'd be very grateful. I do
have access to an EPROM programmer but I don't think it would suffice.
If no 27C64-like PROM chips can be found anymore, a 27C256-like PROM
would do just as well.

Thanks in advance,

Jorden Verwer

don't worry about uv-eproms. I had customer owned equipment coming
back for upgrades mnfctured in 85-87. some were in continous use,
some were tossed aside, but the uv-eproms are always ok. The NV-rams
used in these was another story.