
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
393 of 487
NXP Semiconductors
UM10800
Chapter 26: LPC82x ROM API Power profiles
26.5.1.3 Param3: system PLL lock time-out
It should take no more than 100
s for the system PLL to lock if a valid configuration is
selected. If Param3 is zero, set_pll will wait indefinitely for the PLL to lock. A non-zero
value indicates how many times the code will check for a successful PLL lock event
before it returns PLL_NOT_LOCKED. In this case the PLL settings are unchanged and
Param0 is returned as Result1.
Remark:
The time it takes the PLL to lock depends on the selected PLL input clock
source (IRC/system oscillator) and its characteristics. The selected source can
experience more or less jitter depending on the operating conditions such as power
supply and/or ambient temperature. This is why it is suggested that when a good known
clock source is used and a PLL_NOT_LOCKED response is received, the set_pll routine
should be invoked several times before declaring the selected PLL clock source invalid.
Hint: setting Param3 equal to the system PLL frequency [Hz] divided by 10000 will
provide more than enough PLL lock-polling cycles.
26.5.2 set_power
This routine configures the device’s internal power control settings according to the calling
arguments. The goal is to reduce active power consumption while maintaining the feature
of interest to the application close to its optimum.
Remark:
Use the set_power routine with SYSAHBCLKDIV = 1 (System clock divider
register, see
and
set_power returns a result code that reports whether the power setting was successfully
changed or not.