Does anybody know if _TALLY values are persistent for a given function?

If a timer interrupts and performs something that updates _TALLY, does it update the _TALLY variable visible to the function it interrupted? Is it possible the sequence of events could be:

* Sample code sequence
SELECT * FROM whatever INTO CURSOR c_data
IF _TALLY = 10
    ? "Success"
ENDIF

* 1 ==> SQL SELECT resulting in _TALLY = 10
* 2 ==> Timer fires, executes code which change _TALLY TO 0, returns
* 3 ==> IF _TALLY = 10 is executed and it fails

I wrote a test app with multiple timers and I haven't seen any cases yet after several thousand iterations where it disrupts the visible _TALLY at any given levels. But, this test is not conclusive. It could just be timing coincidence.

Does anybody know?