OTP parts are really EPROM devices without a window to erase
 them.  ROM parts are actually Masked ROM parts.  You have to
 send your code to Microchip, and they hard code it into the
 part.  The result of this is that the parts are much cheaper
 than using OTP parts, if you have enough volume to justify the
 initial setup costs.  Hope this helps.

                                         Regards,

                                          Jim



>I just rec'd the new Microchip line card. Inside they have a new
>category of parts classified as "R" such as 12CR509. The only
>difference they show is that the "R" version is classified as  ROM
>where the others are listed as OTP/Flash. Many of course are not
>flash. OTP is ROM, so what are they getting at here? Or is this just
>another way to classify window parts?
>
>Thanks
>Jack Shidemantle
>Automation & Development Engineer
>YSI, Inc. USA
>