
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
74 of 487
NXP Semiconductors
UM10800
Chapter 6: LPC82x Reduced power modes and power management
–
All registers except the DPDCTRL and GPREG0 to GPREG3 registers and PCON
will be in their reset state.
2. Once the chip has booted, read the deep power-down flag in the PCON register
(
) to verify that the reset was caused by a wake-up event from Deep
power-down and was not a cold reset.
3. Clear the deep power-down flag in the PCON register (
4. (Optional) Read the stored data in the general purpose registers (
).
5. Set up the PMU for the next Deep power-down cycle.
Remark:
The RESET pin has no functionality in Deep power-down mode.
6.7.7.4 Programming Deep power-down mode using the self-wake-up timer:
The following steps must be performed to enter Deep power-down mode when using the
self-wake-up timer for waking up:
1. Enable the low-power oscillator to run in Deep power-down mode by setting bits 2 and
3 in the DPDCTRL register to 1 (see
)
2. Ensure that bit 3 in the PCON register (
) is cleared.
3. Write 0x3 to the PM bits in the PCON register (see
).
4. Store data to be retained in the general purpose registers (
).
5. Write one to the SLEEPDEEP bit in the ARM Cortex-M0+ SCR register.
6. Start the self-wake-up timer by writing a value to the WKT COUNT register
(
7. Use the ARM WFI instruction.
6.7.7.5 Wake-up from Deep power-down mode using the self-wake-up timer:
The part goes through the entire reset process when the self-wake-up timer times out:
1. When the WKT count reaches 0, the following happens:
–
The PMU will turn on the on-chip voltage regulator. When the core voltage reaches
the power-on-reset (POR) trip point, a system reset will be triggered and the chip
re-boots.
–
All registers except the DPDCTRL and GPREG0 to GPREG3 registers and PCON
are in their reset state.
2. Once the chip has booted, read the deep power-down flag in the PCON register
(
) to verify that the reset was caused by a wake-up event from Deep
power-down and was not a cold reset.
3. Clear the deep power-down flag in the PCON register (
4. (Optional) Read the stored data in the general purpose registers (
).
5. Set up the PMU for the next Deep power-down cycle.
Remark:
The RESET pin has no functionality in Deep power-down mode.