SLAZ696H May   2018  – August 2021 MSP430FR2353

 

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6.8 RTC15

RTC Module

Category

Functional

Function

RTC Counter stops operating if RTC Counter clock source is changed from XT1CLK to another source while XT1CLK is stopped

Description

If XT1CLK is used as the clock source for the RTC Counter and XT1CLK stops (e.g. oscillator fault), if the RTC Counter clock source is changed by user software (e.g. in the clock fault handling ISR) from XT1CLK to a different clock source while XT1CLK is stopped the RTC Counter hangs. In this hang state, the RTC Counter stops operating and cannot be restarted without a device reset via the hardware RST pin, a power-cycle of the device, or recovery of XT1CLK oscillation.

Workaround

To change the RTC Counter clock source due to an oscillator fault, in the ISR for handling the OFIFG fault, use this software sequence:

1) Change the RTC Counter clock source away from XT1CLK normally

2) Reconfigure the XIN pin as a GPIO output, then toggle the GPIO twice with at least 2 rising or falling edges.

At this point the RTC Counter will be able to resume operation.