When using the new RTC peripheral, I see that there is an option to enable the subsecond timer.
This is the code it generates:
/* Enable sub-second counter */
RTC_EnableSubsecCounter(HRC_RTC_PERIPHERAL, true);
/* Start RTC timer */
RTC_StartTimer(HRC_RTC_PERIPHERAL);
However, the subsecond timer will not start unless the RTC has been started, making the first call ineffective. The order should be reversed.
As a temporary fix, I have edited my code generator at: \ProgramData\NXP\mcu_data_v15\components\ksdk2_0\lpc_rtc_5b94d23b38d98ad150d835147973adbf\lpc_rtc.component