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Appendix A Electrical Characteristics
MC9S12HZ256 Data Sheet, Rev. 2.05
Freescale Semiconductor
643
A.5.2
Oscillator
The device features an internal Colpitts and Pierce oscillator. The selection of Colpitts oscillator or Pierce
oscillator/external clock depends on the XCLKS signal which is sampled during reset. Pierce
oscillator/external clock mode allows the input of a square wave. Before asserting the oscillator to the
internal system clocks the quality of the oscillation is checked for each start from either power-on, STOP
or oscillator fail. tCQOUT species the maximum time before switching to the internal self clock mode after
POR or STOP if a proper oscillation is not detected. The quality check also determines the minimum
oscillator start-up time tUPOSC. The device also features a clock monitor. A Clock Monitor Failure is
asserted if the frequency of the incoming clock signal is below the Assert Frequency fCMFA.
Table A-16. Oscillator Characteristics
Conditions are shown in
Table A-4 unless otherwise noted
Num
C
Rating
Symbol
Min
Typ
Max
Unit
1a
C Crystal oscillator range (Colpitts)
fOSC
0.5
16
MHz
1b
C Crystal oscillator range (Pierce) 1
1 Depending on the crystal a damping series resistor might be necessary
fOSC
0.5
40
MHz
2
P Startup Current
iOSC
100
A
3
C Oscillator start-up time (Colpitts)
tUPOSC
82
2 f
osc = 4MHz, C = 22pF.
1003
3 Maximum value is for extreme cases using high Q, low frequency crystals
ms
4
D Clock Quality check time-out
tCQOUT
0.45
2.5
s
5
P Clock Monitor Failure Assert Frequency
fCMFA
50
100
200
KHz
6
P External square wave input frequency 4
4 Only valid if Pierce oscillator/external clock mode is selected
fEXT
0.5
50
MHz
7
D External square wave pulse width lo
w4tEXTL
9.5
ns
8
D External square wave pulse width high
4tEXTH
9.5
ns
9
D External square wave rise
time4tEXTR
1ns
10
D External square wave fall
time4tEXTF
1ns
11
D Input Capacitance (EXTAL, XTAL pins)
CIN
7pF
12
C DC Operating Bias in Colpitts Conguration on
EXTAL Pin
VDCBIAS
1.1
V
13
P EXTAL Pin Input High Voltage
4VIH,EXTAL
0.75*VDDPLL
V
T EXTAL Pin Input High Voltage
4VIH,EXTAL
VDDPLL + 0.3
V
14
P EXTAL Pin Input Low Voltage
4VIL,EXTAL
0.25*VDDPLL
V
T EXTAL Pin Input Low Voltage
4VIL,EXTAL
VSSPLL - 0.3
V
15
C EXTAL Pin Input Hysteresis
4VHYS,EXTAL
250
mV