UM10601 Datasheet, PDF (267/313 Pages) NXP Semiconductors – LPC800 User manual

UM10601 NXP
Semiconductors
22.5.1.6 System clock approximately
command[0] = 12000;
command[1] = 16500;
command[2] = CPU_FREQ_APPROX;
command[3] = 0;
(*rom)->pWRD->set_pll(command, result);
Chapter 22:
equal to the
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The above code specifies a 12 MHz PLL input clock, a system clock of approximately
16.5 MHz and no locking time-out. set_pll returns PLL_CMD_SUCCESS in result[0] and
16000 in result[1]. The new system clock is 16 MHz.
22.5.2 Power control
See Section 22.5.1.1 and Section 22.5.2.2 for examples of the power control API.
22.5.2.1 Invalid frequency (device maximum clock rate exceeded)
command[0] = 30;
command[1] = PWR_CPU_PERFORMANCE;
command[2] = 40;
(*rom)->pWRD->set_power(command, result);
The above setup would be used in a system running at the main and system clock of
30 MHz, with a need for maximum CPU processing power. Since the specified 40 MHz
clock is above the 30 MHz maximum, set_power returns PWR_INVALID_FREQ in
result[0] without changing anything in the existing power setup.
22.5.2.2 An applicable power setup
command[0] = 24;
command[1] = PWR_CPU_EFFICIENCY;
command[2] = 24;
(*rom)->pWRD->set_power(command, result);
The above code specifies that an application is running at the main and system clock of
24 MHz with emphasis on efficiency. set_power returns PWR_CMD_SUCCESS in
result[0] after configuring the microcontroller’s internal power control features.
UM10601
Preliminary user manual
All information provided in this document is subject to legal disclaimers.
Rev. 1.0 — 7 November 2012
© NXP B.V. 2012. All rights reserved.
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