Microchip Technology MA160014 データシート

DS41412E-page 40

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For more information about the modes discussed in this
section see 

quick reference list is also available in 

.

When PRI_IDLE mode is selected, the designated
primary oscillator continues to run without interruption.
For all other power-managed modes, the oscillator
using the OSC1 pin is disabled. The OSC1 pin (and
OSC2 pin, if used by the oscillator) will stop oscillating. 

In secondary clock modes (SEC_RUN and
SEC_IDLE), the secondary oscillator (SOSC) is
operating and providing the device clock. The
secondary oscillator may also run in all power-
managed modes if required to clock Timer1, Timer3 or
Timer5.

In internal oscillator modes (INTOSC_RUN and
INTOSC_IDLE), the internal oscillator block provides
the device clock source. The 31.25 kHz LFINTOSC
output can be used directly to provide the clock and
may be enabled to support various special features,
regardless of the power-managed mode (see

 and

 for more

information on WDT, Fail-Safe Clock Monitor and Two-
Speed Start-up). The HFINTOSC and MFINTOSC
outputs may be used directly to clock the device or may
be divided down by the postscaler. The HFINTOSC
and MFINTOSC outputs are disabled when the clock is
provided directly from the LFINTOSC output.

When the Sleep mode is selected, all clock sources are
stopped. Since all the transistor switching currents
have been stopped, Sleep mode achieves the lowest
current consumption of the device (only leakage
currents).

Enabling any on-chip feature that will operate during
Sleep will increase the current consumed during Sleep.
The LFINTOSC is required to support WDT operation.
Other features may be operating that do not require a
device clock source (i.e., SSP slave, PSP, INTn pins
and others). Peripherals that may add significant
current consumption are listed in 

Power-up delays are controlled by two timers, so that
no external Reset circuitry is required for most
applications. The delays ensure that the device is kept
in Reset until the device power supply is stable under
normal circumstances and the primary clock is
operating and stable. For additional information on
power-up delays, see 

.

The first timer is the Power-up Timer (PWRT), which
provides a fixed delay on power-up. It is enabled by
clearing (= 0) the PWRTEN Configuration bit. 

The second timer is the Oscillator Start-up Timer
(OST), intended to keep the chip in Reset until the
crystal oscillator is stable (LP, XT and HS modes). The
OST does this by counting 1024 oscillator cycles
before allowing the oscillator to clock the device.

When the PLL is enabled with external oscillator
modes, the device is kept in Reset for an additional
2 ms, following the OST delay, so the PLL can lock to
the incoming clock frequency.

There is a delay of interval T

CSD

, following POR, while

the controller becomes ready to execute instructions.
This delay runs concurrently with any other delays.
This may be the only delay that occurs when any of the
EC, RC or INTIOSC modes are used as the primary
clock source.

When the HFINTOSC is selected as the primary clock,
the main system clock can be delayed until the
HFINTOSC is stable. This is user selectable by the
HFOFST bit of the CONFIG3H Configuration register.
When the HFOFST bit is cleared, the main system
clock is delayed until the HFINTOSC is stable. When
the HFOFST bit is set, the main system clock starts
immediately. 

In either case, the HFIOFS bit of the OSCCON register
can be read to determine whether the HFINTOSC is
operating and stable.