Ben wrote:
as well as not knowing of where to get
ferromagnetic? ram. I want real non-voiltile memory.
Ramtron ferroelectric RAM (nonvolatile) is available from Newark
Electronics. The traditional problem with FRAM is that it had limited
read endurance, as well as limited write endurance. Just reading the
part would wear it out. The newest 3V parts have fixed that.
The FM18L08 is a 32K*8 3V 70ns part with unlimited endurance. IIRC,
the last time I bought some from Newark I paid under $10 each.
There is a newer 128K*8 55ns part, the FM20L08. Newark doesn't have
it yet. All American Direct gives a price of $25.59, but it is not
clear whether they actually have parts in stock.
If you want to use these in a 5V system, it's probably a good idea
to use some 74LVC buffers that can function as level translators.
There are also some 128K*8 nonvolatile parts from Simtek, e.g.,
STK14CA8 and STK16CA8. They are not ferroelectric, but instead combine
SRAM and flash on one part, with automatic transfers between the two at
powerup and powerdown. Since they use SRAM, they are much faster
than the Ramtek parts. They also respond to a series of writes to magic
addresses to allow software controlled transfers, in a manner similar
to the Dallas Semiconductor battery-backed RAM with RTC. Although the
probability of accidental activation of that feature is miniscule,
I still don't much like it.
Eric