Ron Kneusel wrote:
There is also an EPROM (or, what I naively call an EPROM: has a little window on it presumably to erase it?)
Yes, that would be an EPROM - Erasable Programmable Read-Only Memory. The 'little window' is indeed used to erase the contents, by placing the chip under a UV light source for a length of time.
The window should, in practice, normally be covered with a sticker impervious to UV light since there's a component of UV in natural and most artificial lights and chances are that prolonged exposure will inadvertently 'erase' bits.
Regards, -- Mark McDougall, Engineer Virtual Logic Pty Ltd, <http://www.vl.com.au> 21-25 King St, Rockdale, 2216 Ph: +612-9599-3255 Fax: +612-9599-3266