UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 34 of 841
NXP Semiconductors
UM10360
Chapter 4: LPC176x/5x Clocking and power control
point, software can control switching to the main oscillator as a clock source. Prior to
starting the main oscillator, a frequency range must be selected by configuring the
OSCRANGE bit in the SCS register.
4.3.3 RTC oscillator
The RTC oscillator provides a 1 Hz clock to the RTC and a 32 kHz clock output that can
be used as the clock source for PLL0 and CPU and/or the watchdog timer.
Remark: The RTC oscillator must not be used as a clock source when the PLL0 output is
selected to drive the USB controller. In this case select the main oscillator as clock source
for PLL0 (see also Table 17
).