Power Saving Modes
C513AO
User’s Manual
9-4
05.99
As in Normal Operation Mode, the ports can be used as inputs during Idle Mode. Thus, a capture
or reload operation can be triggered, the timers can be used to count external events, and external
interrupts will be detected.
As discussed below, Idle Mode is a useful feature which makes it possible to “freeze” the
processor’s status - either for a predefined time or until an external event reverts the controller to
normal operation.
Idle Mode is entered by setting the IDLE (PCON.0) bit. Since PCON is not a bit-addressable
register, the setting of this bit is achieved by byte-handling instructions. For example:
ORL
PCON,#00000001B
; Set IDLE bit
The instruction which sets bit IDLE is the last instruction executed before going into Idle Mode.
There are two ways to terminate Idle Mode:
– Idle Mode can be terminated by activating any enabled interrupt. This interrupt will be serviced
and, normally, the instruction to be executed following the RETI instruction will be the one
following the instruction that sets the bit IDLE.
– The other way to terminate Idle Mode, is a hardware reset. Since the oscillator is still running,
the hardware reset must be held active only for two machine cycles for a complete reset.
Note: The Watchdog Timer is the only peripheral which is stopped automatically during Idle Mode.