Re: Why and when flash memory is needed in embedded system?

"John" <javacc1@xxxxxxxxx> wrote in message
news:1158825604.736539.96750@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

David Ashley wrote:
I think some form of non-volatile memory is needed in a system
of any complexity. I can picture an ASIC or CPLD that does
something useful yet has no non-volatile memory. Like a
sound effect generator, one button switches sounds, the other
button turns sound generation on.


If the embedded system doesn't have flash memory, how can it boot up??
I keep thinking flash memory or ROM is used for boot up process.

is that true? please advice more....

ROM is not necessarily Flash. Flash is just a convenient method of being
able to reprogram ROM chips. In the old days ROM consisted of fuses that
were blown so the data was permanently etched into the memory. Later on
erasable ROMs became avaiable but you had to shine UV light on them to
clear.

Speaking to a very old hairy-eared engineered once he told be that the
ROM he used many many years ago was windings of copper wire with ferrite
beads on them to represent data. Apparently they always used women to
wind the wires because they were more accurate than men. But I
digress....

As long as there is some kind of memory available to the processor that
is not lost when the power is removed (so it is non-volatile) then it
will be able to boot. Flash is one type of possible memory (and the most
common) but so is battery backed Static RAM or an old-school PROM or a
number of other methods.


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