MSP430FR6989: What are LFXT_OF, HFXT_OF, and NMIRS?

Hi Thomas,

Thanks for your detailed question.

Thomas Foxcroft said:

• It shows LFXT_OF and HFXT_OF as being bitfields, but there are no registers having those bitfields. Nor does the header file have definitions for them. Can anybody tell me why?
• Isn't LFXT_OscFault the same as LFXT_OF? Likewise with HFXT_OscFault?

I see your point. Looking at this diagram, I suspect it was one from early development that never got updated. In the CS Module Fail-Safe Operation section of the User's Guide, it says the following:

The crystal oscillator fault bits LFXTOFFG and HFXTOFFG are set if the corresponding crystal oscillator is turned on and not operating properly. Once set, the fault bits remain set until reset in software, even if the fault condition no longer exists. If the user clears the fault bits and the fault condition still exists, the fault bits are automatically set; otherwise, they remain cleared.

Looking at the diagram, I can see that the LFXTOFFG and HFXTOFFG flip-flops can only get reset by POR (which goes high during a POR request, then automatically cleared). Those flip-flops cannot be reset by software like the LFXT_OF and HFXT_OF flip-flops can be, but like you mentioned, these outputs aren't mentioned in the User's Guide.

Thus, it seems like functionality of each pair of flip-flops have been combined into a single flip-flop. I'll submit a request to have the diagram updated in the future.

Thomas Foxcroft said:

It shows NMIRS as a signal going out of that block of logic, but there is no definition for that signal. Is it NMI reset, NMI request, or what? Does anybody know what it really is?

NMIRS means Non Maskable Interrupt Request Signal and illustrates a user NMI request when OFIFG and OFIE are set.

Thomas Foxcroft said:

And what exactly is NMI _IRQA?

NMI_IRQA means the NMI interrupt request has been accepted.

Regards,

James