Renesas RA Family
RA2 Quick Design Guide
R01AN6060EU0100 Rev.1.00
Page 17 of 44
Sep.14.21
Figure 11. Equivalent Circuit of the Crystal Resonator
Selection of the capacitor values for CL1 and CL2 will affect the accuracy of the internal clock. To
understand the impact of the values for CL1 and CL2, the circuit should be simulated using the equivalent
circuit of the crystal resonator in the figure above. For more accurate results, also take in to account the stray
capacitance associated with the routing between the crystal resonator components.
5.10 External Clock Input
A digital clock input may be used as the main clock source for most RA2 devices. Figure 12 shows an
example of connecting an external clock input. To operate the oscillator with an external clock signal, set the
MOMCR.MOSEL bit to 1. The XTAL pin becomes high impedance.
Figure 12. Equivalent circuit for external clock
Notes
: The frequency of the external clock input can only be changed when the main clock oscillator is
stopped. Do not change the frequency of the external clock input when the setting of the Main Clock
Oscillator Stop bit (MOSCCR.MOSTP) is 0.
6. Reset Requirements and the Reset Circuit
There are 12 or 13 types of resets for Arm
®
Cortex-M23 devices.
