The maximum operating frequency varies depending on the operating voltage value for each model number.
In the case of the model number in the image below, it can be driven at an operating frequency of 32MHz when the supply voltage is higher than 2.5V, but when operating from 1.8V, the operating frequency may be up to 16MHz, so be careful. Is required.
The device in the image has a maximum operating frequency of 16MHz when driven by 1.8V.

Therefore, when checking the operating frequency, it is necessary to check the operating voltage in the datasheet.

For PIC16LF1559