R01DS0140ED0100_FJ4_15 Datasheet, PDF (27/78 Pages) Renesas Technology Corp – 32-bit Single-Chip Microcontroller

Chapter 4
Clock generators
The main oscillator amplifier gain for the external resonator can be selected by
MOSCC.MOSCCAMPSEL[1:0]. Thereby it can be adjusted to support a wide
range of frequencies to cope with different external resonators and their
external circuitry.
As an example a typical setting for quartz crystals is shown in Table 4-3
“Typical setting of MOSCC.AMPSEL[1:0] for different quartz crystals
frequencies”.
Note
Table 4-3
For details to the setting of MOSCC.MOSCCAMPSEL[1:0] please refer to the
user manual.
Typical setting of MOSCC.AMPSEL[1:0] for different quartz crystals
frequencies
MOSCC.AMPSEL[
1:0]
00
01
10
11
Amplification
gain
high
medium
low
very low
Typical condition for quartz
crystals
16 < f_MOSC ≤ 20 MHz
8 < f_MOSC ≤ 16 MHz
4 < f_MOSC≤ 8 MHz
4 MHz
(1) Main oscillator charactrisitics
Table 4-4 Main oscillator characteristics
Parameter
MainOSC frequency
Symbol
f_MOSC
Condition
Ratings
Min Typ Max
4
-
20
Unit
MHz
Cautions 1. External clock input is prohibited.
2. General guidance for PCB layout:
• Keep the wiring length as short as possible.
• Do not cross the wiring with other signal lines.
• Do not route this circuit close to a signal line with high fluctuating current
flow.
• Always make the ground point of the oscillator capacitor the same
potential as REG0VSS and OSCVSS.
• Do not ground the capacitor to a ground pattern with high current flow.
• Do not tap signals from the oscillator.
4.3.2 Sub-oscillator
A crystal resonator can be connected to the sub clock input pins as shown in
figure 4-2 “Recommended Sub Oscillator Circuit”
R01DS0140ED0100
27
Data Sheet