MSP430FR6989: Why clearing the LOCKLPM5 bit after configuring the I/Os in instead of before?

Sara Souza

Expert 1450 points

Part Number: MSP430FR6989

I'd like to know why should I do this before instead of after if this bit unlocks the I/Os.

over 8 years ago

0 Clemens Ladisch over 8 years ago

Guru 317500 points

Clearing LOCKLPM5 immediately applies the current settings of the configuration registers to the pins. And these settings might be wrong (otherwise, you wouldn't need to configure the I/Os).

0 Sara Souza over 8 years ago in reply to Clemens Ladisch

Expert 1450 points

Sorry,

but if these settings are wrong it's going to remain wrong either if you clear LOCKLPM5 before or after setting the I/Os, isn't it?

0 Clemens Ladisch over 8 years ago in reply to Sara Souza

Guru 317500 points

No, because your I/O configuration changes the settings.

If you clear LOCKLPM5 first, then the pins get the current settings. Then your code changes the configuration, which changes the pins again.
If you change the configuration first, then the pins stay at the reset configuration. Then, when LOCKLPM5 is cleared, the pins change to the new settings.

0 Sara Souza over 8 years ago in reply to Clemens Ladisch

Expert 1450 points

Got it!
Thank you!

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MSP430FR6989: Why clearing the LOCKLPM5 bit after configuring the I/Os in instead of before?