Post by thread:Aghhh Code Protection Bit Problem .... (fwd)

part 0 26415 bytes content-type:TEXT/PLAIN; CHARSET=US-ASCII hi there, Yesterday my worst nightmare occured, I think I may have inadvertently programmed the code protection bit on my PIC16C74JW. I'm not sure exactly how this happened. I have been using a home made programmer very succesfully up until now, but this time something strange happened the pic blankchecked ok programmed ok and then failed the verify.. At first I wasn't too worried but then I read back the code with a different package and this told me that the code protect bit had been set. Needless to say I was pretty disturbed that my 40 IRpounds chip had been effectively ruined. What I would like to find out from the list is 1. Is there anyway of undoing the code protect ?? (I assume not !) 2. If I cant undo the code protect is there any way I can reprogram the chip, even if I can't verify the code I write ? 3. If I buy a new chip what are the chances of me doing this again. 4. Am I correct in assuming that it only takes a one bit error when reprogramming the PIC to actually wreck your PIC. 5. Where are the fuses stored in memory are they part of the hex code you read back or is there a special bus instruction to access the fuses area of the pics. Is there any way I can be sure If I get another PIC that I don't do this again. Even if there is a hardware error in my programming. What I mean is for example If the download method is as follows 1. Send start signal 2. Download bit stream of CODE to PIC 3. Follow directly with bit stream of FUSES 010010.. etc 4. END If the above assumption is correct then I would be worried that a single bit error in the fuses stream could destroy my second PIC. However if on the other hand it follows the pattern of 1. Send Start Signal 2. Download bit stream of CODE to PIC 3. Send "Prepare to recieve FUSES code" (If fuses are to be set) 4. Now send Fuses bit stream. 5. END With the latter arrangement It could be possible to only program the code area and never send the "Prepare to recieve FUSES". This way I could be quite sure not to accidently set a CP FUSE. Assuming my spurious error doesn't send the correct byte to prepare for fuses.. (Fairly safe.) However I just realised I probably need to set my crystal fuse.. Aghhh is there any way to be safe.. One bit really isn't a big error for the price of the chip.. Anyway sorry for such a long posting. Any help or comments appreciated.. Thanks. David. P.S. I've included my original hex and readback code in case anyone can magically look at such cryptic figures and go " Ahh I know what happend" (Not likely I'd say) Everyone else delete at will !. Http://http://www.csn.ul.ie/~david Content-Type: TEXT/PLAIN; CHARSET=US-ASCII; NAME="RS232.HEX" Content-ID: <spam_OUTPine.LNX.3.95.970212162652.20083BTakeThisOuTskynet.csn.ul.ie>> Content-Description: original hex :020000000528D1 :08000800142888018316880109 :1000100020308C0019309900A43098008312903061 :100020009800C0308B00132806301805031D1E28C9 :100030008C1E09001A088800990009001812181669 :06004000FF3088000900FA :00000001FF Content-Type: TEXT/PLAIN; CHARSET=US-ASCII; NAME="READBACK.HEX" Content-ID: <.....Pine.LNX.3.95.970212162652.20083CKILLspam@spam@skynet.csn.ul.ie>> Content-Description: read back code. :100000002A007F007F007F003B00740051007400D5 :100010003F007200060067003A00660059000E00BB :1000200066005E0075003C0019006D00460031005E :100030004E007600750076006700760043004B00A6 :100040006100760076007F007F007F007F007F00E8 :100050007F007F007F007F007F007F007F007F00A8 :100060007F007F007F007F007F007F007F007F0098 :100070007F007F007F007F007F007F007F007F0088 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>David, > > Not that it is any consolation but I am looking at 3 PIC16C62A/JWs > out of a group of 5 that I had been using. These 3 all mysteriously > got code protected. Even though I have been especially careful and > am using a Microchip Promate programmer, it still happened. I understand that on HC705 series any code protection is via EPROM bit, I infer that code protection on PIC is via a fuse and therefore cannot be erased by UV ? Does this also apply to the flash parts - wouldn't it be more efficient that the code protection be via EPROM type bit anyway ? Are there any moves by microchip (hi guys) to change to EPROM bit ? And in any case since I hear that all code protected PIC parts are just as easy to read as the code protected motorola parts - wouldn't it be logical that a code protect chip could be erased and reused ? Rgds Mike

On Thu, 13 Feb 1997, Mike wrote: > >David, > > > > Not that it is any consolation but I am looking at 3 PIC16C62A/JWs > > out of a group of 5 that I had been using. These 3 all mysteriously > > got code protected. Even though I have been especially careful and > > am using a Microchip Promate programmer, it still happened. > > I understand that on HC705 series any code protection is via EPROM bit, > I infer that code protection on PIC is via a fuse and therefore cannot > be erased by UV ? Yeah I'd imagine so ! > > Does this also apply to the flash parts - wouldn't it be more efficient > that the code protection be via EPROM type bit anyway ? > > Are there any moves by microchip (hi guys) to change to EPROM bit ? > I hate to say it but I recon judging by previous discussions I have heard that the move was actually in the other direction. I reckon that it may have been due to a worry by microchip that one may be able to selectively erase parts of the windowed chip using perhaps a fine laser beam or something. And by doing so only wipe the CP bit.. I.e. exposing the protected code.. I am no expert on the subject so all I have just said is purely hearsay. Please correct me if I'm wrong in those assumptions. However on the note of Microchip doing something about the problem I would suggest and hope I'm taken seriously that a variant of the windowed chip be produced that has no code protect bit.. Surely this wouldn't be difficult (I realise Chip changes incur fabrication costs ) but I believe there would definately be a large market for such chips as most developers have no need to code protect their windowed versions.. It's easier to lock them in your drawer ! Could anyone who agrees with this suggestion please voice your support to confrim such a market. > And in any case since I hear that all code protected PIC parts are just > as easy to read as the code protected motorola parts - wouldn't it be > logical that a code protect chip could be erased and reused ? > Hmmmm, Are you sure on that one ? I'm sure microchip wouldn't be impressed ! > Rgds > > > Mike > Dave. http://www.csn.ul.ie/~david

Seems like they could have added a bit "code protect disable". When this fuze gets blown, you can nolonger code protect. This would allow us to make the chip "un-protectable" for development and still be able to protect them for production. If the code protect is enabled before code protect disable, then the chip would forever be code protected. If the code protect disable was "enabled" before the code protect, the chip would be un-protected forever. Both bits should be un eraseable. Any thoughts. Norm At 06:34 PM 2/12/97 +0000, you wrote: {Quote hidden}>On Thu, 13 Feb 1997, Mike wrote: > >> >David, >> > >> > Not that it is any consolation but I am looking at 3 PIC16C62A/JWs >> > out of a group of 5 that I had been using. These 3 all mysteriously >> > got code protected. Even though I have been especially careful and >> > am using a Microchip Promate programmer, it still happened. >> >> I understand that on HC705 series any code protection is via EPROM bit, >> I infer that code protection on PIC is via a fuse and therefore cannot >> be erased by UV ? > >Yeah I'd imagine so ! > >> >> Does this also apply to the flash parts - wouldn't it be more efficient >> that the code protection be via EPROM type bit anyway ? >> >> Are there any moves by microchip (hi guys) to change to EPROM bit ? >> > I hate to say it but I recon judging by previous discussions I >have heard that the move was actually in the other direction. I reckon >that it may have been due to a worry by microchip that one may be able to >selectively erase parts of the windowed chip using perhaps a fine laser >beam or something. And by doing so only wipe the CP bit.. I.e. exposing >the protected code.. > I am no expert on the subject so all I have just said is purely >hearsay. Please correct me if I'm wrong in those assumptions. > However on the note of Microchip doing something about the problem >I would suggest and hope I'm taken seriously that a variant of the >windowed chip be produced that has no code protect bit.. Surely this >wouldn't be difficult (I realise Chip changes incur fabrication costs ) >but I believe there would definately be a large market for such chips as >most developers have no need to code protect their windowed versions.. >It's easier to lock them in your drawer ! Could anyone who agrees with >this suggestion please voice your support to confrim such a market. > > > > > >> And in any case since I hear that all code protected PIC parts are just >> as easy to read as the code protected motorola parts - wouldn't it be >> logical that a code protect chip could be erased and reused ? >> > > Hmmmm, Are you sure on that one ? I'm sure microchip wouldn't be >impressed ! > >> Rgds >> >> >> Mike >> > > > Dave. > > > >http://www.csn.ul.ie/~david > >

I agree We are planning to introduce the PIC to the Scottish Education system as my teacher now has a job involving this. We sure could do with this as pupils, code protect and chip prices don't go well together. Tim At 12:58 12/02/97 -0600, you wrote: {Quote hidden}>Seems like they could have added a bit "code protect disable". When this >fuze gets blown, you can nolonger code protect. This would allow us to >make the chip "un-protectable" for development and still be able to protect >them for production. If the code protect is enabled before code protect >disable, then the chip would forever be code protected. If the code >protect disable was "enabled" before the code protect, the chip would be >un-protected forever. Both bits should be un eraseable. > >Any thoughts. > >Norm > ------------------------------------------------------------------ If you can read this, it is the end of the message! My web pages are at http://web.ukonline.co.uk/members/tim.kerby/ My PIC site is at web.ukonline.co.uk/members/tim.kerby/pic/ It needs your projects! ------------------------------------------------------------------

On Wed, 12 Feb 1997, Tim Kerby wrote: > Hey, is it a 74 or 74A? > I think the 74 can be uv erased. If you have been using the 74 and this > chip is a 74a then some config bits are inverted possibly including code > protect. > > > Tim Actually I'm using the 16C74. And I haven't tried UV erasing it yet. Actually I was afraid to erase it in case someone came back and said ... " Well you can actually undo the code protect bit as long as you don't attempt to UV erase it first ! ". Not likely to happen at this stage. I don't have access to an eraser until tommorow so I'll let you know if it works. I had been under the impression though that the policy was that all new PICs would have fuse CP's thus only the older 74's in stock would be UV erasable. Also can someone confirm what Tim mentioned about the CP bits being inverted on 74A. My programmer software is supposed to support 74A. I'm not sure yet how it knows what chip it is ?? Although I had programmed before using same software... Dave. http://www.csn.ul.ie/~david > > > ------------------------------------------------------------------ > If you can read this, it is the end of the message! > My web pages are at http://web.ukonline.co.uk/members/tim.kerby/ > My PIC site is at web.ukonline.co.uk/members/tim.kerby/pic/ > It needs your projects! > ------------------------------------------------------------------ >

Absolutely.. This sounds like the best idea yet !! On Wed, 12 Feb 1997, Norm Cramer wrote: {Quote hidden}> Seems like they could have added a bit "code protect disable". When this > fuze gets blown, you can nolonger code protect. This would allow us to > make the chip "un-protectable" for development and still be able to protect > them for production. If the code protect is enabled before code protect > disable, then the chip would forever be code protected. If the code > protect disable was "enabled" before the code protect, the chip would be > un-protected forever. Both bits should be un eraseable. > > Any thoughts. > > Norm > > At 06:34 PM 2/12/97 +0000, you wrote: > >On Thu, 13 Feb 1997, Mike wrote: > > > >> >David, > >> > > >> > Not that it is any consolation but I am looking at 3 PIC16C62A/JWs > >> > out of a group of 5 that I had been using. These 3 all mysteriously > >> > got code protected. Even though I have been especially careful and > >> > am using a Microchip Promate programmer, it still happened. > >> > >> I understand that on HC705 series any code protection is via EPROM bit, > >> I infer that code protection on PIC is via a fuse and therefore cannot > >> be erased by UV ? > > > >Yeah I'd imagine so ! > > > >> > >> Does this also apply to the flash parts - wouldn't it be more efficient > >> that the code protection be via EPROM type bit anyway ? > >> > >> Are there any moves by microchip (hi guys) to change to EPROM bit ? > >> > > I hate to say it but I recon judging by previous discussions I > >have heard that the move was actually in the other direction. I reckon > >that it may have been due to a worry by microchip that one may be able to > >selectively erase parts of the windowed chip using perhaps a fine laser > >beam or something. And by doing so only wipe the CP bit.. I.e. exposing > >the protected code.. > > I am no expert on the subject so all I have just said is purely > >hearsay. Please correct me if I'm wrong in those assumptions. > > However on the note of Microchip doing something about the problem > >I would suggest and hope I'm taken seriously that a variant of the > >windowed chip be produced that has no code protect bit.. Surely this > >wouldn't be difficult (I realise Chip changes incur fabrication costs ) > >but I believe there would definately be a large market for such chips as > >most developers have no need to code protect their windowed versions.. > >It's easier to lock them in your drawer ! Could anyone who agrees with > >this suggestion please voice your support to confrim such a market. > > > > > > > > > > > >> And in any case since I hear that all code protected PIC parts are just > >> as easy to read as the code protected motorola parts - wouldn't it be > >> logical that a code protect chip could be erased and reused ? > >> > > > > Hmmmm, Are you sure on that one ? I'm sure microchip wouldn't be > >impressed ! > > > >> Rgds > >> > >> > >> Mike > >> > > > > > > Dave. > > > > > > > >http://www.csn.ul.ie/~david > > > > >

> On Wed, 12 Feb 1997, Norm Cramer wrote: > > Seems like they could have added a bit "code protect disable". When this > > fuze gets blown, you can nolonger code protect. This would allow us to > > make the chip "un-protectable" for development and still be able to protect > > them for production. If the code protect is enabled before code protect > > disable, then the chip would forever be code protected. If the code > > protect disable was "enabled" before the code protect, the chip would be > > un-protected forever. Both bits should be un eraseable. > > > > Any thoughts. > Absolutely.. > This sounds like the best idea yet !! I prefer a slightly different variant: the device incorporates a code-protect bit and a code-protect-write-enable bit. When an OTP is shipped from the factory, the latter bit is set; for a UV device it is not set. While it would be possible for a programmer to--with enough trouble--burn the protect-enable pin and then burn the protect bits themselves, this would not happen without deliberate action. As a simpler alternative, Microchip could simply document the behavior of one of their "test" locations sufficiently to say that it will be blank on all UV devices and non-blank on OTP's. A programmer could then simply decline to code-protect any device whose test area was blank. This alternative may be the best because it could be accomplished with no change to the die whatso- ever; only a slight change in handling (to erase the window parts before ship- ping them) and in the documentation. On a related note: is there any reliable (blessed by Microchip) method of identifying a part to be programmed? Programming a 16C622 as though it's a 16C84 seems to damage the poor thing rather severely...