UM11029
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© NXP Semiconductors N.V. 2017. All rights reserved.
User manual
Rev. 1.0 — 16 June 2017
117 of 515
NXP Semiconductors
UM11029
Chapter 8: LPC84x System configuration (SYSCON)
To avoid glitches when powering down the FRO, the FRO clock is automatically switched
off at a clean point. Therefore, for the FRO a delay is possible before the power-down
state takes effect.
The system oscillator requires typically 500
μ
s to start up after the SYSOSC_PD bit has
been changed from 1 to 0. There is no hardware flag to monitor the state of the system
oscillator. Therefore, add a software delay of about 500
μ
s before using the system
oscillator after power-up.
Table 172. Power configuration register (PDRUNCFG, address 0x4004 8238) bit description
Bit
Symbol
Value
Description
Reset value
0
FRO
OUT_PD
FRO
oscillator output power
0
0
Powered
1
Powered down
1
FRO
_PD
FRO
oscillator power down
0
0
Powered
1
Powered down
2
FLASH_PD
Flash power down
0
0
Powered
1
Powered down
3
BOD_PD
BOD power down
1
0
Powered
1
Powered down
4
ADC_PD
ADC wake-up configuration
1
0
Powered
1
Powered down
5
SYSOSC_PD
Crystal oscillator power down. After power-up,
add a software delay of approximately 500
μ
s
before using.
1
0
Powered
1
Powered down
6
WDTOSC_PD
Watchdog oscillator power down. Changing
this bit to powered-down has no effect when
the LOCK bit in the WWDT MOD register is
set. In this case, the watchdog oscillator is
always running.
1
0
Powered
1
Powered down
7
SYSPLL_PD
System PLL power down
1
0
Powered
1
Powered down
9:8
-
Reserved. Always write these bits as 0b01
0b01
12:10
-
Reserved. Always write these bits as 0b011
0b011
13
DAC0
DAC0 power down
1
0
Powered
1
Powered down