MC9S12A256 Device Guide — V01.01
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A.5.1.4 Stop Recovery
Out of STOP the controller can be woken up by an external interrupt. A clock quality check as after POR
is performed before releasing the clocks to the system.
A.5.1.5 Pseudo Stop and Wait Recovery
The recovery from Pseudo STOP and Wait are essentially the same since the oscillator was not stopped in
both modes. The controller can be woken up by internal or external interrupts. After twrs the CPU starts
fetching the interrupt vector.
A.5.2 Oscillator
The device features an internal Colpitts oscillator. By asserting the XCLKS input during reset this
oscillator can be bypassed allowing 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 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 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-15 Oscillator Characteristics
Conditions are shown in Table A-4 unless otherwise noted
Num C
Rating
Symbol
Min
Typ
Max
Unit
1
C Crystal oscillator range
fOSC
0.5
16
MHz
2
P Startup Current
iOSC
100
A
3
C Oscillator start-up time
tUPOSC
81
NOTES:
1. fosc = 4MHz, C = 22pF.
1002
2. 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
6P External square wave input frequency3
3. XCLKS =0 during reset
fEXT
0.5
50
MHz
7
D External square wave pulse width low
tEXTL
9.5
ns
8
D External square wave pulse width high
tEXTH
9.5
ns
9
D External square wave rise time
tEXTR
1ns
10
D External square wave fall time
tEXTF
1ns
11
D Input Capacitance (EXTAL, XTAL pins)
CIN
9pF
12
C
DC Operating Bias in Colpitts Configuration on
EXTAL Pin
VDCBIAS
1.1
V