Cortex M4, guidance for an i/o assembly tuition

I have two month ago started to familiarise myself with programming my Cortex M4, with C and just getting very well aquainted. As my background is in the ATMEL, Motorola, Zilog 8/16 bit assembly arena, the learning curve is rather steep- as you probably agree with me. ?  Do you know a good i/o assembly tuition. ?

Thanking you.

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