How to understand the VIOOH/VIOOL voltage level in the datasheet? Does these level match with peripheral (for example UART) of a 3rd party device?
In the datasheet of EFM32 device, you could see the VIOOH/VIOOL voltage at different drive mode and current when applied different power supply voltage.
Take the EFM32PG1 as example, you could see below data in table 4.15 on page 22:
Assume IOVDD=3.3V, VIOOH is 0.80*VDD = 2.64V, VIOOL is 0.2*VDD = 0.66V.
Though these data seems like are too high for VIOOL and low for VIOOH, it was characterized under the current 3mA. If the target device don't need so high current, the VIOOH and VIOOL would be expected to be more close to IOVDD rail voltage.