UM10375 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
User manual Rev. 3 — 14 June 2011 58 of 368
NXP Semiconductors
UM10375
Chapter 5: LPC13xx Power profiles
command[3] = 0;
(*rom)->pWRD->set_pll(command, result);
The above code specifies a 12 MHz PLL input clock, a system clock of no more than
40 kHz and no time-out while waiting for the PLL to lock. Since the maximum divider value
for the system clock is 255 and running at 40 kHz would need a divide by value of 300,
set_pll returns PLL_INVALID_FREQ in result[0] and 12000 in result[1] without changing
the PLL settings.
5.5.1.4.3 Exact solution cannot be found (PLL)
command[0] = 12000;
command[1] = 25000;
command[2] = CPU_FREQ_EQU;
command[3] = 0;
(*rom)->pWRD->set_pll(command, result);
The above code specifies a 12 MHz PLL input clock and a system clock of exactly
25 MHz. The application was ready to infinitely wait for the PLL to lock. Since there is no
valid PLL setup within earlier mentioned restrictions, set_pll returns
PLL_FREQ_NOT_FOUND in result[0] and 12000 in result[1] without changing the PLL
settings.
5.5.1.4.4 System clock less than or equal to the expected value
command[0] = 12000;
command[1] = 25000;
command[2] = CPU_FREQ_LTE;
command[3] = 0;
(*rom)->pWRD->set_pll(command, result);
The above code specifies a 12 MHz PLL input clock, a system clock of no more than
25 MHz and no locking time-out. set_pll returns PLL_CMD_SUCCESS in result[0] and
24000 in result[1]. The new system clock is 24 MHz.
5.5.1.4.5 System clock greater than or equal to the expected value
command[0] = 12000;
command[1] = 25000;
command[2] = CPU_FREQ_GTE;
command[3] = 0;
(*rom)->pWRD->set_pll(command, result);
The above code specifies a 12 MHz PLL input clock, a system clock of at least 25 MHz
and no locking time-out. set_pll returns PLL_CMD_SUCCESS in result[0] and 36000 in
result[1]. The new system clock is 36 MHz.
5.5.1.4.6 System clock approximately equal to the expected value
command[0] = 12000;
command[1] = 16500;
command[2] = CPU_FREQ_APPROX;
command[3] = 0;
(*rom)->pWRD->set_pll(command, result);
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