|
PXN20RM Datasheet, PDF (120/1376 Pages) Freescale Semiconductor, Inc – PXN20 Microcontroller | |||
|
◁ |
System Clock Description
â Clock source from external oscillator
â Lock detect circuitry continuously monitors lock status
â Loss of clock (LOC) detection for reference and feedback clocks
â On-chip loop filter (for improved electromagnetic interference performance and reduces
number of external components required)
â Programmable frequency modulation
⢠On-chip crystal oscillator (4 â 40 MHz XTAL) supporting 4 MHz to 40 MHz crystals
⢠Dedicated 16 MHz internal RC oscillator
â 16 MHz internal RC oscillator supports low speed code execution and clocking of peripherals
through selection as the system clock
â Used as default clock source out of reset
â Provides a clock for rapid start-up from low power modes
â Provides a back-up clock in the event of PLL or external oscillator clock failure
â Provides watchdog timer
â 5% accuracy over the operating temperature range (after factory trim)
â Trimming registers to support frequency adjustment with in-application calibration
⢠Dedicated internal 128 kHz_IRC oscillator for low power mode operation and self wake-up
â 5% accuracy (after factory trim)
â Trimming registers to support improve accuracy with in-application calibration
⢠Dedicated 32 kHz_XTAL external oscillator for accurate timed wake-up
5.1.2 Clock Sources
The PXN20 clock sources are:
⢠High Frequency Crystal oscillator (4 â 40 MHz XTAL)
⢠Fast on-chip RC oscillator (16 MHz_IRC)
⢠Slow on-chip RC oscillator (128 kHz_IRC)
⢠32 kHz crystal oscillator (32 kHz_XTAL)
⢠Phase-Locked Loop (FMPLL)
The clock sources available on the PXN20 are shown in Figure 5-1 and discussed in more detail in
subsequent sections.
PXN20 Microcontroller Reference Manual, Rev. 1
5-2
Freescale Semiconductor
|
▷ |