On Wed, 21 Jul 1999 15:28:22 -0700 "William K. Borsum"
<borsum@DASCOR.COM> writes:

>I have an application where I need to log data at the rate of up to
>200
>K-bytes per second, to a depth of 120-160 Mega-bytes.
>Part of the problem is that it is memory is broken up into a series of
>ring
>buffers that are sequentially  over-written till an event occurs,

Consider using this logic:  While waiting for the event, keep writing
through all the memory over and over again.  When the event occurs, save
the address which corresponds to data written at the time of the event.
Then continue writing until you're about to overwrite the last
pre-trigger data you need to save.

This method is easy to program, and it also distributes wear over the
entire memory.  If you use 200 Kbytes per second, and a capacity of 120
Mbytes, each location is only re-written once per ten minutes while
waiting.  The recorder can run in the "waiting for trigger" mode for
about *19 years* before a location will have been re-written 1 million
times.

So it's not out of the question to use flash.  But I'd lean toward DRAM
because of the large capacity required.


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