I received on Tue, 22 Aug 1995 18:44:59 from Mike Keitz : > Subject: Re: Ready for non-window pics > > Martin Kirk wrote: > >Hi, > > > >Will someone please give me a brief list of the requirements for clearing > >the registers when moving one's code to non-windowed pics? I assume it > >is a simple clear all registers operation. Please confirm. > > > > AFAIK, the non-window PICs have *exactly* the same chip in them as the > window ones. So there should be no difference in operation between one type > and the other, other than inability to erase the non-window one. > > (In an earlier thread, someone noted that newer versions of the window chips > have a non-erasable code protect bit. So if this bit is set, a windowed > chip would be non-reusable as well. Has Microchip issued an exact statement > on this?) I have two PIC17C44-JW (windowed) engineering samples, one now a doorstop, the other now a paperweight. Microchip did confirm that the code-protect on these windowed parts is not erasable. One representative told me that there is some kind of metal or metalization over those fuses. Since the dice are exactly the same in windowed and OTP parts, this is obviously intended to make it more difficult for a would-be hacker to split open an OTP package and create his/her own ``window'' to selectively erase the code-protect fuse of a code-protected part. When I posted my speculations on the MCHIPBBS about the implementation (some fuse bits are eraseable, some are not) it was removed and I was sent a private BBS mail message explaining that management was understandably touchy about the topic. The only difference between windowed and non-windowed parts is that an erased windowed part tends to come up initialized the same way every time, with zeros in lots of places which should not be relied upon. Peter F. Klammer, Racom Systems Inc. PKlammer@ACM.Org 6080 Greenwood Plaza Boulevard (303)773-7411 Englewood, CO 80111 FAX:(303)771-4708