Rev. 1.10
62
October 23, 2020
Rev. 1.10
63
October 23, 2020
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
Prescaler
f
H
High Speed
Oscillators
f
H
/2
f
H
/16
f
H
/64
f
H
/8
f
H
/4
f
H
/32
CKS2~CKS0
f
SYS
f
SUB
f
SUB
f
LIRC
SLEEP
IDLE0
IDLE2
SLEEP
HIRC
HIRCEN
LXT
Low Speed
Oscillators
FSS
LIRC
LXTEN
f
LIRC
f
LIRC
FHS
HXT
HXTEN
System Clock Configurations
External Crystal/Ceramic Oscillator – HXT
The External Crystal/Ceramic System Oscillator is one of the high frequency oscillator choices,
which is selected via a software control bit, FHS. For most crystal oscillator configurations, the
simple connection of a crystal across OSC1 and OSC2 will create the necessary phase shift and
feedback for oscillation, without requiring external capacitors. However, for some crystal types
and frequencies, to ensure oscillation, it may be necessary to add two small value capacitors, C1
and C2. Using a ceramic resonator will usually require two small value capacitors, C1 and C2,
to be connected as shown for oscillation to occur. The values of C1 and C2 should be selected in
consultation with the crystal or resonator manufacturer’s specification.
For oscillator stability and to minimise the effects of noise and crosstalk, it is important to ensure
that the crystal and any associated resistors and capacitors along with interconnecting lines are all
located as close to the MCU as possible.
Note:
To internal
circuits
Internal
Oscillator
Circuit
C1
C2
OSC1
OSC2
R
F
R
P
1. R
P
is normally not required. C1 and C2 are required.
2. Although not shown OSC1/OSC2 pins have a parasitic capacitance of around 7pF.
Crystal/Ceramic Oscillator – HXT
HXT Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
16MHz
0pF
0pF
12MHz
0pF
0pF
8MHz
0pF
0pF
6MHz
0pF
0pF
4MHz
0pF
0pF
1MHz
100pF
100pF
Note: C1 and C2 values are for guidance only.
Crystal Recommended Capacitor Values