BH66F2470 Datasheet, PDF (53/223 Pages) Holtek Semiconductor Inc – Glucose Meter Flash MCU

BH66F2470
Glucose Meter Flash MCU
High Speed
Oscillators
HXT
HIRC
Low Speed
Oscillators
LXT
LIRC
FHS
IDLE0
SLEEP
Prescaler
IDLE2
SLEEP
FSS
fLIRC
System Clock Configurations
fH
fH/2
fH/4
fH/8
fH/16
fSYS
fH/32
fH/64
fSUB
CKS2~CKS0
fSUB
External Crystal/Ceramic Oscillator – HXT
The External Crystal/Ceramic System Oscillator is one of the high frequency oscillators. 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.
C1
OSC1
Internal
Oscillator
Circuit
RP
RF
To internal
C2
OSC2
circuits
Note: 1. RP is normally not required. C1 and C2 are required.
2. Although not shown OSC1/OSC2 pins have a parasitic
capacitance of around 7pF.
Crystal/Resonator Oscillator
Crystal Oscillator C1 and C2 Values
Crystal Frequency
C1
C2
16MHz
0pF
0pF
12MHz
0pF
0pF
8MHz
0pF
0pF
4MHz
0pF
0pF
1MHz
100pF
100pF
Note: C1 and C2 values are for guidance only.
Crystal Recommended Capacitor Values
Rev. 1.00
53
March 15, 2017