NXP Semiconductors KL25 Series - Freescale Semiconductor, Inc

PIT_LDVAL0 = 0xFFFFFFFF; // setup timer 0 for maximum counting period
PIT_TCTRL0 = TEN; // start timer 0
To access the lifetime, read first LTMR64H and then LTMR64L.
current_uptime = PIT_LTMR64H<<32;
current_uptime = current_uptime + PIT_LTMR64L;
Chapter 32 Periodic Interrupt Timer (PIT)
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 585