I have an interesting problem.
I am using the MSP‑EXP430FR4133 and playing with the 32kHz crystal (connected to P4.1 and P4.2) and the RTC.
I set up the RTC in the following way:
RTCCTL = RTCSS__XT1CLK | RTCSR | RTCPS__1 | RTCIE; // XCO, reset, no divider, interrupt enable
The surprising thing is that the RTC seems to work even without setting P4SEL0 = BIT1 | BIT2. Infact, it even works with me explicitly setting P4SEL0 = 0.
According to the MSP430FR4133 datasheet (page 57) this simply shouldn't work, because the pins the XTAL is connected to will not be connected to the clock system.
Any suggestions about what's going on?