PIC18F2331 Datasheet, PDF (35/396 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High Performance PWM and A/D

PIC18F2331/2431/4331/4431
TABLE 3-2: COMPARISON BETWEEN POWER-MANAGED MODES
Power
Managed
Mode
CPU is clocked by ...
WDT time-out
causes a ...
Peripherals are
clocked by ...
Clock during wake-up
(while primary becomes
ready)
Sleep
Not clocked (not running) Wake-up
Any idle mode Not clocked (not running) Wake-up
Any run mode Secondary, or INTOSC Reset
multiplexer
Not clocked
Primary, Secondary or
INTOSC multiplexer
Secondary or INTOSC
multiplexer
None or INTOSC multiplexer
if Two-Speed Start-up or
Fail-Safe Clock Monitor are
enabled.
Unchanged from Idle mode
(CPU operates as in
corresponding Run mode).
Unchanged from Run mode.
3.2 Sleep Mode
The power-managed Sleep mode in the PIC18F2331/
2431/4331/4431 devices is identical to that offered in
all other PICmicro^® controllers. It is entered by clearing
the IDLEN and SCS1:SCS0 bits (this is the Reset
state), and executing the SLEEP instruction. This shuts
down the primary oscillator and the OSTS bit is cleared
(see Figure 3-1).
When a wake event occurs in Sleep mode (by interrupt,
Reset, or WDT time-out), the system will not be clocked
until the primary clock source becomes ready (see
Figure 3-2), or it will be clocked from the internal oscil-
lator block if either the Two-Speed Start-up or the Fail-
Safe Clock Monitor are enabled (see Section 22.0
“Special Features of the CPU”). In either case, the
OSTS bit is set when the primary clock provides the
system clocks. The IDLEN and SCS bits are not
affected by the wake-up.
3.3 Idle Modes
The IDLEN bit allows the controller’s CPU to be selec-
tively shut down while the peripherals continue to oper-
ate. Clearing IDLEN allows the CPU to be clocked.
Setting IDLEN disables clocks to the CPU, effectively
stopping program execution (see Register 2-2). The
peripherals continue to be clocked regardless of the
setting of the IDLEN bit.
There is one exception to how the IDLEN bit functions.
When all the low-power OSCCON bits are cleared
(IDLEN:SCS1:SCS0 = 000), the device enters Sleep
mode upon the execution of the SLEEP instruction. This
is both the Reset state of the OSCCON register and the
setting that selects Sleep mode. This maintains com-
patibility with other PICmicro devices that do not offer
power-managed modes.
If the Idle Enable bit, IDLEN (OSCCON<7>), is set to a
‘1’ when a SLEEP instruction is executed, the
peripherals will be clocked from the clock source
selected using the SCS1:SCS0 bits; however, the CPU
will not be clocked. Since the CPU is not executing
instructions, the only exits from any of the idle modes
are by interrupt, WDT time-out or a Reset.
When a wake event occurs, CPU execution is delayed
approximately 10 µs while it becomes ready to execute
code. When the CPU begins executing code, it is
clocked by the same clock source as was selected in
the power-managed mode (i.e., when waking from
RC_IDLE mode, the internal oscillator block will clock
the CPU and peripherals until the primary clock source
becomes ready – this is essentially RC_RUN mode).
This continues until the primary clock source becomes
ready. When the primary clock becomes ready, the
OSTS bit is set, and the system clock source is
switched to the primary clock (see Figure 3-4). The
IDLEN and SCS bits are not affected by the wake-up.
While in any idle mode or the Sleep mode, a WDT time-
out will result in a WDT wake-up to full power operation.
 2003 Microchip Technology Inc.
Preliminary
DS39616B-page 33