PXN20RM Datasheet, PDF (122/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller

System Clock Description
— jitter < 0.5%
— duty cycle: 50% ±10%
• Clock source can be kept alive in Sleep mode to facilitate fast start up. However, if > 8 MHz is
required, it cannot drive the RTC/API as the output driver needs to be disabled.
• Can be stopped in low power mode to reduce current consumption
• PLL Off mode to reduce consumption with external clock
• External square-wave input with PLL Off mode XTAL enabled by default out of Reset, turned off
for Square wave i/p
5.1.4 Internal High-Frequency RC Oscillator (16 MHz_IRC)
This internal RC oscillator provides a 16 MHz clock source to the device. The initial trimming value is
copied into the trimming register during power on reset (POR). The device’s individual value is
determined during one of the silicon test steps and stored in the device test Flash block. Until the Flash is
up and stable, the IRC runs at its untrimmed frequency.
5.1.4.1 16 MHz_IRC Features
• 16 MHz_IRC is the default system clock out of reset. This clock features the following:
— Clock for rapid startup from low power modes
— Can be configured to run in Sleep mode
— Backup clock in case of external oscillator or PLL failure
• Fast stabilization, enabling fast recovery
• Frequency trimmable for accuracy
• Powered from V_RC (3.3 V or 5 V nominal)
• Always enabled except in sleep modes when not being used (disabled in hardware only)
• The 16 MHz_IRC block contains no dividers of its own.
5.1.5 Internal Low-Frequency RC Oscillator (128 kHz_IRC)
The PXN20 includes a 128 kHz internal RC oscillator that is a highly reliable clock source during
low-power modes. This internal RC oscillator provide a 128 kHz clock source to the device. The initial
trimming value is copied into the trimming register during power on reset. This device’s individual value
is determined during one of the silicon test steps and stored in the device test Flash block. This trim value
is retained through Sleep mode.
5.1.5.1 128 kHz_IRC Features
The 128 kHz_IRC clock features the following:
• Frequency trimmable for accuracy
• Option to clock the API to provide a wakeup
• Option to clock the RTC to provide timekeeping
PXN20 Microcontroller Reference Manual, Rev. 1
5-4
Freescale Semiconductor