I am interfacing MAX232 with STM32F030k6. I have very recently found out that Max3232 would be a better choice, because it works with 3,3 volt. But I am eager to know if UART reciever pin of the mentioned MCU is 5 Volt tolerant. On the other side, I know that MAX232 recognizes any voltage higher that 2V as 5V. Therefore That wouldn't become a trouble. I have took a look at my MCU user manual but didn't find anything. I appreciate your ideas on this issue.
The manual (https://www.st.com/resource/en/datasheet/stm32f030f4.pdf) on page 28 has the info about the I/O structure:
I am sorry to inform you that it is not 5V tolerant.
You could use a simple voltage divider on the USART input (RX) to bring it down to a more compatible level.
Better yet, you could use UART on other pins as their alternate function. If you look at the same table 11 that starts on page 28, you will start seeing USART in the "Pin functions" > "Alternate functions" column. Match that with the "FT" or "FTf" abbreviations in the "I/O structure" column, and you've got yourself a 5V tolerant UART interface.
(Thanks to @Justme who kept on insisting that we dig for more information!)
Not all pins are 5V tolerant. You haven't mentioned which pin you are using, but the datasheet lists the IO pin type so when you know which pin is used you can see if it is 5V tolerant or not. PA3 is not 5V tolerant, but the other three pins than can be mapped to USART1_RX are.