When Active Clock Tuning is enabled (ACTEN =
1) and either the ACTLOCK or ACTORS bits change
state (e.g., from a Locked to an Unlocked state), the ACT
Interrupt Flag (ACTIF) of the PIR registers is set (ACTIF =
1). If the ACT Interrupt Enable
(ACTIE) bit is set (ACTIE = 1), an interrupt
will be generated when ACTIF becomes set. No interrupts are
generated for each OSCTUNE update
unless the update results in a change of Lock status or
Out-of-Range status.