Recommendation for Hardware Setup 32-Bit FR81S Family
Document No. 002-09375 Rev. *B
5
2.8
C-Pin
A 4.7 µF ceramic capacitor (dielectric X7R) must be connected very close to the C pin of the MCU. Furthermore, an
additional 100 nF (dielectric X7R) for higher noise frequencies is recommended. Otherwise the MCU may not operate
correct or will be damaged in worst case. Please refer to Datasheet chapter “Recommended operating conditions” for
further information.
Figure 3. Internal Voltage Regulator and C Pin
MCU
GPIO
GPIO
GPIO
G
P
IO
G
P
IO
G
P
IO
G
P
IO
GPIO
GPIO
GPIO
G
P
IO
O
S
C
G
P
IO
Vcc
Vcc
5V
Vcc
Vss
G
N
D
Vss
GND
5V
5V
5V
G
N
D
Vss
GND
Vcc
Vss
C
Internal 1.2V
Vss
GND
4.7µF
(ceramic X7R)
CORE
internal
voltage
regulator
*1
Note *1 : Vss pin
closest to C pin
2.9
Clock Source
A clock source must be provided to the MCU. Therefore, crystals or external clock signals can be used. For external
source pin X0 (X0A) is used whereby pin X1 (X1A) is not connected.
There are MCU derivatives for dual clock and single clock devices, the sub clock can be enabled by software. If sub
clock X0A pin is neither used as GPIO nor as clock input, the pin can be left open.
If you want to use only CR clock, then you need a MCU version with disabled CSV.
Please also refer to the
chapter “Handling the device” in the corresponding hardware manual for details.
