The dedicated X1 and X2 pins support an external
clock source (XTAL), which can be used as the main system and auxiliary clock source.
Frequency limits and timing requirements can be found in the device data sheet. Three types
of external clock sources are supported:
- A single-ended 3.3V external clock. The clock
signal must be connected to X1 while X2 is left unconnected, as shown in Figure 3-6.
- An external crystal. The crystal must be
connected across X1 and X2 with the load capacitors connected to VSSOSC as shown in Figure 3-7.
- An external resonator.
The resonator must be connected across X1 and X2 with the ground connected to VSSOSC as
shown in Figure 3-8.
Note: All 3 external clocking modes require the
XTALOFF bit in CLKSRCCTL1 register to be set to 0. This enables the path and circuitry
required for the clock to propagate to the device.