NXP Semiconductors LPC11U1x, User Manual

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User manual Rev. 5.5 — 21 December 2016 66 of 523
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Chapter 5: LPC11U3x/2x/1x Power profiles
For a simplified clock configuration scheme see Figure 11 . For more details see Figure 7 .
5.7.1.1 Param0: main clock
The main clock is the clock rate the microcontroller uses to source the system’s and the
peripherals’ clock. It is configured by either a successful execution of the clocking routine
call or a similar code provided by the user. This operand must be an integer between 1 to
50 MHz inclusive. If a value out of this range is supplied,
set_power returns
PWR_INVALID_FREQ and does not change the power control system.
5.7.1.2 Param1: mode
The input parameter mode ( Param1 ) specifies one of four available power settings. If an
illegal selection is provided, set_power returns PWR_INVALID_MODE and does not
change the power control system.
PWR_DEFAULT keeps the device in a baseline power setting similar to its reset state.
PWR_CPU_PERFORMANCE configures the microcontroller so that it can provide more
processing capability to the application. CPU performance is 30% better than the default
option.
PWR_EFFICIENCY setting was designed to find a balance between active current and
the CPU’s ability to execute code and process data. In this mode the device outperforms
the default mode both in terms of providing higher CPU performance and lowering active
current.
PWR_LOW_CURRENT is intended for those solutions that focus on lowering power
consumption rather than CPU performance.
5.7.1.3 Param2: system clock
The system clock is the clock rate at which the microcontroller core is running when
set_power is called. This parameter is an integer between from 1 and 50 MHz inclusive.
5.7.1.4 Code examples
The following examples illustrate some of the set_power features discussed above.
5.7.1.4.1 Invalid frequency (device maximum clock rate exceeded)
command[0] = 60;
command[1] = PWR_CPU_PERFORMANCE;
command[2] = 60;
(*rom)->pWRD->set_power(command, result);
The above setup would be used in a system running at the main and system clock of
60 MHz, with a need for maximum CPU processing power. Since the specified 60 MHz
clock is above the 50 MHz maximum,
set_power returns PWR_INVALID_FREQ in
result[0] without changing anything in the existing power setup.
5.7.1.4.2 An applicable power setup
command[0] = 24;
command[1] = PWR_CPU_EFFICIENCY;
command[2] = 24;