
Appendix A Electrical Characteristics
MC9S12E128 Data Sheet, Rev. 1.07
576
Freescale Semiconductor
A.3.2
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-12. 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
1Depending 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
2f
osc = 4MHz, C = 22pF.
1003
3Maximum 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
6P External square wave input frequency 4
4Only valid if Pierce oscillator/external clock mode is selected
fEXT
0.5
50
MHz
7D External square wave pulse width lo
w4tEXTL
9.5
ns
8D External square wave pulse width high
4tEXTH
9.5
ns
9D 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
VIH,EXTAL 0.75*VDDPLL
V
VIH,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