>> OK, that's news. I was under the impression that an FPGA works something
>> like an EPROM - you use UV to erase it and then program in all the
>> circuit connections, and thereafter it just works.
> 
> Some are OTP (one time programmable) but most are flash based today.

A PROM is OTP; an EPROM (Erasable PROM) can be reused.

An EPROM usually works by having a little lense over the die surface, 
through which you fire UV radiation to cause chemical changes in the 
chip material which either 'connects' or 'disconnects' circuit pathways, 
thus forming a ROM.

I was under the impression that FPGAs work in the same way, except 
instead of opening and closing contacts between data lines and the power 
rails to make bit patterns, you actually connect and disconnect blocks 
of circuitry to make a custom circuit configuration.

Of course, flash RAM uses chemical changes to permanently store data 
too; you just don't need the lense and the UV radiation. But I didn't 
think you could use that technology to physically change connections...

> Atmel makes CPLDs and FPGAs, too.

Right, OK.

-- 
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