Re: Memory selection for an embedded system

The types of memories that you mentioned, SDRAM, SRAM, FLASH, and
EEPROM, all have certain features that make them an advantage or
dis-advantage in certain situations. For example, SDRAM will be fast
and high density per dollar, but it requires a refresh circuit which
isn't necessarilly feasible on an embedded application. Therefore,
SRAM is often times use instead as it doesn't require this, but it is a
bit slower (70ns is typical I think) and slightly more expensive. The
last time I looked, a 256K x 16 SRAM chip on digikey was about $4 for
one device, which for most embedded systems, unless you call pentium
computers running windows an embedded system, which I don't, is a lot
of memory. Flash, on the other hand is non volatile, fairly high
density and is reprogrammable, often times used as ROM while EEPROM is
also nonvolatile, but fairly low density and speed.

The choice of which type of memory you select depends on the goal of
the application and a typical system will likely have multiple form of
memory in it.

.

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