zeroing enums and bit variables at startup

[SteveK]

Hi there,

I am using the watchdog on a 18F452 to cause the software to carry on from where it left off, ie without program initialisations. I am careful to initialise my variables only if it is a genuine powerup or brownout restart cause.

I have some enums, some of which have only two states, and are stored by the compiler as bit variables.

On a watchdog restart, the whole byte (at addres 0x02EE) which contains 8 bit variables is cleared, though I never set or clear any of these flags/enums through the watchdog restart path.

I also don't have these varibles initialised at the declaraion time.

Is this known behaviour? Can it be turned off? (Using PCWH 3.241)


Many thanks for your help,
Steve

[PCM programmer]

According to the .LST file, the following test program does not clear
the 'mode' variable upon reset. I tested this with PCH vs. 3.241
and 3.245.

Are you using the #zero_ram directive ? If so, then 'mode' will be
cleared upon reset.

[Ttelmah]

Do you declare the variables as 'static'?.
If so, the compiler will clear them.
This behaviour changed, a long time ago. The manual will tell you that a static variable will be cleared. Remember that if you declare a variable externally to the main code, it will become functionally static anyway, and in this case will not be cleared (this was what was changed - a long time ago, the compiler would treat such 'default static' variables as if they were static, and clear them as well, which was a pain!...).
So, if I declare:

[SteveK]

Hi guys,

Thanks so much for your responses. PCM programmer, no, I was not using the #zero ram directive.

Ttelmah, you have hit the nail on the head. I have declared the enum as a static within a function, so that it would keep its value between calls to that function.

The cure, of course, is simply to declare the enum as a global in main part of the program.

I will try this now - if I don't post again, assume all is well :-).

Many thanks again,
Steve