31.1.3 LPTMR prescaler/glitch filter clocking options
The prescaler and glitch filter of the LPTMR module can be clocked from one of four
sources determined by LPTMR0_PSR[PCS]. The following table shows the chip-specific
clock assignments for this field.
NOTE
The chosen clock must remain enabled if the LPTMR is to
continue operating in all required low-power modes.
LPTMR0_PSR[PCS]
Prescaler/glitch filter clock
number
Chip clock
00
0
MCGIRCLK—internal reference clock
(not available in LLS and VLLS modes)
01
1
LPO—1 kHz clock (not available in
VLLS0 mode)
10
2
ERCLK32K (not available in VLLS0
mode when using 32 kHz oscillator)
11
3
OSCERCLK—external reference clock
(not available in VLLS0 mode)
See
for more details on these clocks.
31.2 Introduction
The low-power timer (LPTMR) can be configured to operate as a time counter with
optional prescaler, or as a pulse counter with optional glitch filter, across all power
modes, including the low-leakage modes. It can also continue operating through most
system reset events, allowing it to be used as a time of day counter.
31.2.1 Features
The features of the LPTMR module include:
• 16-bit time counter or pulse counter with compare
• Optional interrupt can generate asynchronous wakeup from any low-power mode
• Hardware trigger output
• Counter supports free-running mode or reset on compare
• Configurable clock source for prescaler/glitch filter
• Configurable input source for pulse counter
• Rising-edge or falling-edge
Introduction
KL27 Sub-Family Reference Manual , Rev. 5, 01/2016
502
Freescale Semiconductor, Inc.
