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STM32L4 GPIO Behavior on Shutdown

N.F. Singh
Associate II

I've read through the datasheet and reference manual for STM32L451REI and have been trying to nail down some definitive answers for GPIO behavior upon SHUTDOWN mode. I can't seem to find them, so I'll ask here.

In SHUTDOWN MODE:

  1. are pullups/pulldowns fully active as configured prior to entering shutdown?
  2. what happens to a push-pull that was HIGH prior to shutdown? Does it go LOW? Floating? Hi-Z?
  3. what happens to an open-drain? Does it just float, and are pullups/downs still active?

Trying to make sure I understand behavior so I don't see erratic behavior or excess current usage.

Thanks,

1 REPLY 1

Settings in GPIO are not used in Standby mode, the pins are either completely floating; or pullups/pulldowns can be applied by setting APC bit in PWR_CR3 and then the individual PWR_PUCRx/PWR_PDCRx bits. Read the I/O states in Standby mode subchapter in RM0394.

There are exceptions - the SWD pins can't have any of pullup/pulldown applied, and the RTC pins may be under control of RTC, see RTC chapter.

JW