Datasheet

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. t
CQOUT
specifies 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 t
UPOSC
. 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 f
CMFA
.
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)
f
OSC
0.5 16 MHz
1b C
Crystal oscillator range (Pierce)
1
1
Depending on the crystal a damping series resistor might be necessary
f
OSC
0.5 40 MHz
2 P Startup Current
i
OSC
100 µA
3 C Oscillator start-up time (Colpitts)
t
UPOSC
8
2
2
f
osc
= 4MHz, C = 22pF.
100
3
3
Maximum value is for extreme cases using high Q, low frequency crystals
ms
4 D Clock Quality check time-out
t
CQOUT
0.45 2.5 s
5 P Clock Monitor Failure Assert Frequency
f
CMFA
50 100 200 KHz
6P
External square wave input frequency
4
4
Only valid if Pierce oscillator/external clock mode is selected
f
EXT
0.5 50 MHz
7D
External square wave pulse width low
4
t
EXTL
9.5 ns
8D
External square wave pulse width high
4
t
EXTH
9.5 ns
9D
External square wave rise time
4
t
EXTR
1ns
10 D
External square wave fall time
4
t
EXTF
1ns
11 D Input Capacitance (EXTAL, XTAL pins)
C
IN
7pF
12 C
DC Operating Bias in Colpitts Configuration on
EXTAL Pin
V
DCBIAS
1.1 V
13 P
EXTAL Pin Input High Voltage
4
V
IH,EXTAL
0.75*V
DDPLL
V
T
EXTAL Pin Input High Voltage
4
V
IH,EXTAL
V
DDPLL
+ 0.3
V
14 P
EXTAL Pin Input Low Voltage
4
V
IL,EXTAL
0.25*V
DDPLL
V
T
EXTAL Pin Input Low Voltage
4
V
IL,EXTAL
V
SSPLL
- 0.3
V
15 C
EXTAL Pin Input Hysteresis
4
V
HYS,EXTAL
250 mV