tmr0 16f877

[Liviu M]

Cand dai un sfat, e indicat sa-l si motivezi (ca sa-l inteleaga si cel caruia il adresezi, ca altfel il ia de woodoo). Asa ca te rog sa si explici de ce e nevoie de volatile.

Ce stiu eu despre volatile asta e ce-am citit prin manualul de la picc.

 

Extras din manualul PICC9.80a

3.3.10.2 VOLATILE TYPE QUALIFIER

The volatile type qualifier is used to tell the compiler that an object cannot be guaranteed

to retain its value between successive accesses. This prevents the optimizer

from eliminating apparently redundant references to objects declared volatile

because it may alter the behavior of the program to do so.

Any SFR which can be modified by hardware or which drives hardware is qualified as

volatile, and any variables which may be modified by interrupt routines should use

this qualifier as well. For example:

volatile static unsigned int TACTL @ 0x160;

The volatile qualifier does not guarantee that any access will be atomic, which is

often not the case with the PIC10/12/16 architecture, which can only access a maximum

of 1 byte of data per instruction.

The code produced by the compiler to access volatile objects may be different to

that to access ordinary variables, and typically the code will be longer and slower for

volatile objects, so only use this qualifier if it is necessary. However failure to use

this qualifier when it is required may lead to code failure.