mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 573

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

A.3.2
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
POR or STOP if a proper oscillation is not detected. The quality check also determines the minimum
oscillator start-up time t
asserted if the frequency of the incoming clock signal is below the Assert Frequency f
Freescale Semiconductor
1
2
3
4
Conditions are shown in
Num C
1a
1b
10
11
12
13
14
15
Depending on the crystal a damping series resistor might be necessary
f
Maximum value is for extreme cases using high Q, low frequency crystals
Only valid if Pierce oscillator/external clock mode is selected
2
3
4
5
6
7
8
9
osc
= 4MHz, C = 22pF.
C Crystal oscillator range (Colpitts)
C Crystal oscillator range (Pierce)
P Startup Current
C Oscillator start-up time (Colpitts)
D Clock Quality check time-out
P Clock Monitor Failure Assert Frequency
P External square wave input frequency
D External square wave pulse width low
D External square wave pulse width high
D External square wave rise time
D External square wave fall time
D Input Capacitance (EXTAL, XTAL pins)
C DC Operating Bias in Colpitts Configuration on
P EXTAL Pin Input High Voltage
P EXTAL Pin Input Low Voltage
C EXTAL Pin Input Hysteresis
T EXTAL Pin Input High Voltage
T EXTAL Pin Input Low Voltage
EXTAL Pin
Oscillator
CQOUT
Table A-4
UPOSC
specifies the maximum time before switching to the internal self clock mode after
Rating
unless otherwise noted
. The device also features a clock monitor. A Clock Monitor Failure is
4
Table A-12. Oscillator Characteristics
4
4
4
4
4
4
1
MC9S12E256 Data Sheet, Rev. 1.08
4
4
4
V
V
V
V
V
Symbol
V
HYS,EXTAL
t
t
IH,EXTAL
IH,EXTAL
IL,EXTAL
IL,EXTAL
UPOSC
CQOUT
f
t
t
t
t
DCBIAS
f
f
i
CMFA
f
EXTL
EXTH
EXTR
EXTF
OSC
OSC
OSC
C
EXT
IN
0.75*V
V
SSPLL
0.45
Min
100
0.5
0.5
0.5
9.5
9.5
50
—
—
—
—
—
—
—
—
DDPLL
– 0.3
Appendix A Electrical Characteristics
Typ
100
250
1.1
—
—
—
8
—
—
—
—
—
—
—
—
—
7
2
V
CMFA
0.25*V
DDPLL
100
Max
200
2.5
16
40
50
—
—
—
—
—
—
—
1
1
.
DDPLL
3
+ 0.3
Unit
MHz
MHz
MHz
KHz
mV
ms
pF
ns
ns
ns
ns
V
V
V
V
V
s
A
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