STM32L4 GPIO Behavior on Shutdown

[N.F. Singh]

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,

[waclawek.jan]

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