Post by thread:[PIC]: selective programming

Hi Folks, I've just come back from my vacation to be hit with this question. I believe it is possible but I'm not sure how difficult it is to do. If anyone has any comments I'd appreciate it. The Question: Using a 16F628 (or 16F876 ) can I, load a piece of code into an area of memory and code protect it. Then at a later stage load some new code into the remaining memory, which can make calls to the protected code. I know the bootloaders do something of this ilk but I don't wish to use bootloading - I need to be able to use a picstart or similar programmer. I am aware there are issues around the making of the calls etc when generating/compiling the second batch of code. It is just the feasibility of the hardware side I'm interested in at the moment. Slan John -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

> The Question: > Using a 16F628 (or 16F876 ) can I, load a piece of code into > an area of > memory and code protect it. Then at a later stage load some > new code into > the remaining memory, which can make calls to the protected > code. No. Protection = protect everything, so no new reads or writes unless you erase (everything) first. Check the 18f PICs where this is possible to some extent. I don't know about the 16f8xA and 16f8xxA, might be possible with them too. Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

Hi Wouter, Thanks for your reply. Although it wasn't what I wished to hear it does clarify somewhat. However I do have a thought which may prove to be of help for my requirement. It all hinges on whether the PICSTART always does a bulk erase or not. If it does then I'll have to look at a more "flexible" programmer. On reading the programming spec I see that there is selective code protection for blocks of memory. This means that initially I can programme the first piece of code and protect the block (e.g. 400 -7ff). Now if I come along later and selectively write to the remaining memory(e.g. 0 -3ff) - but without doing a bulk erase first - I can get in the second part of the code. The issue I see here is that if I then want to protect all the code it could cause a bulk erase which puts me back at square one. My gut feel on this issue is that if I leave the configuration word at it's unprogrammed state ( all 1s - I'm assuming) and just write a zero to the one bit for the 400 - 7ff block protection, I can then set all the other bits (low) as required on the second programming run. I don't think this would constitute a "reset" of the configuration word and thus no bulk erase caused. What do you think? Slan John -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> (snip about partial protection and reprogramming without erasing) > What do you think? Sorry, I am not familiar with the exeact algorithm used by PS+, so I cannot comment. For my own programmer [Byron, are you reading? ;] and PC software shuch slective programming should be possible, although I never tested it. Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads