I am just learning MCUs and am working with a PIC24EP. I am in the process of learning about external crystal oscillators. I have a HC49US 20MHz crystal, but some things I have read online talk about making sure the output is compatible with the MCU voltage input. I am confused by this. The PIC24EP is a 3.3v device. The HC49US crystal datasheet does not say anything about voltage. Is there something I am missing here? Can this crystal be used with any PIC that can accept a 20MHz input regardless of whether it is 5V or 3.3V?