#FUSES NOPROTECT and PROTECT

srikrishna · Joined: 06 Sep 2017 Posts: 82

Any one can explain me Why we use #FUSES NOPROTECT and #FUSES PROTECT in code??
i have read the manual it says
#FUSES NOPROTECT //Code not protected from reading

what does it mean by Code not protected from reading??

Ttelmah · Joined: 11 Mar 2010 Posts: 19539

It means if you stick the chip into a programmer, and try to read it, you won't get the code back.
There are quite a few 'variants' depending on the chip involved.

1) On old chips you could read an encrypted form of the code. Quite difficult to decode, but meant you could read it from a 'known working' chip, and then compare this to verify that the programming had worked OK.
On more modern chips you just get 'blank' data back, so have to verify before setting this fuse.
2) Many chips have other options, allowing different parts of the code to be protected.

Designed to help protect commercial code from being copied.

There is a big 'downside' to this when developing code, that once set, it can only be turned off by a full chip erase. This uses a memory 'life' for the whole chip, every time you want to change anything. Otherwise the programmer can be 'smart' and only change parts that need to be changed.
So only turn it on if you need to protect the code, and only after you have the code working.

UserJP · Joined: 13 Oct 2017 Posts: 2

If you have set the #noprotect fuse, your program memory can be read. This is not directly the code you wrote (because if it were it would be reverse engineering, and this is very very difficult), it is machine language with some cryptography done by the compiler.

see:

temtronic · Posted: Fri Oct 13, 2017 9:44 am

re:

Ttelmah · Joined: 11 Mar 2010 Posts: 19539

This does depend on the PIC.
As I tried to explain. On all PIC's, if unprotected, a programmer can read the machine code.
On older PIC's if protected, you get back an encrypted version of the code. It can be broken but is hard.
On newer PIC's if protected you get back nothing.