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STM32F4: GPIOx_AFRL/H value vs. GPIOx_MODER AF mode

Question asked by PICguy on Jul 25, 2014
Latest reply on Jul 25, 2014 by waclawek.jan
What is the use of the GPIOx_MODER Alternate function mode?  Is it needed when an appropriate non-zero value is put into GPIOx_AFRL/H?  Is the GPIOx_MODER alternate function mode value only needed for those few alternates using GPIOx_AFRL/H AF=0?

Does the alternate function take over the entire GPIO port bit.  Or are GPIOx_OSPEEDR and GPIOx_PUPDR settings used as specified by the values stored in these registers?

(I have never had the occasion to use any AF=0 alternate functions.  When setting a non-zero alternate function have a tendency to set alternate function mode in GPIOx_MODER.  My guess is that I am doing something unnecessary.)