Explain Output Speed STM32U575

[ScottD]

I am working on the firmware for my STM32U575 based controller board. I cannot find in the documentation an explanation about the Low/Medium/High settings on a GPIO port. I see the bits to be set, and in MX the option for choosing the setting, but I cannot find an explanation regarding when to use Low vs Medium vs High speed. What is affected by choosing the different speeds? is it rise/fall time, response time, power drive,...? I tried to find a table or something that explains the difference so I can determine whether I need to go to medium or high speed for various signals. What is the purpose of having these speed settings?

[KnarfB]

It is in the DS13737 Rev 10 STM32U575xx data sheet Table 96 ff. Output AC characteristics...

hth

KnarfB

[STOne-32]

Dear @ScottD ,

to complement the information given by @KnarfB  which available in the datasheet . The I/O speed will act on the rise/fall time and you can see the effect especially with VDD 3,3 range or 1,8V ranges and also on the Bus/line Load such as 15pF, 30pF .  In general, if no High speed I/F are required it is recommended to use the lowest speed to minimise EMI and  signals reflection especially when the line impedance are not matching the drive . You can also use our IBIS models for advanced simulation for PCB/Board design https://www.st.com/resource/en/application_note/an4803-highspeed-si-simulations-using-ibis-and-boardlevel-simulations-using-hyperlynx-si-on-stm32-mcus-and-mpus-stmicroelectronics.pdf and you can see the effect of the speed .

Hope it helps you 

STOne-32