MC9S12A256 Motorola, MC9S12A256 Datasheet - Page 112

• Manufacturer Part Number: MC9S12A256
• Description: MC9S12DT256 Device User Guide V03.03
• Manufacturer: Motorola

MC9S12DT256 Device User Guide — V03.03
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 t
fetching the interrupt vector.
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.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. t
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
Clock Monitor Failure is asserted if the frequency of the incoming clock signal is below the Assert
Frequency f
Conditions are shown in Table A-4 unless otherwise noted
Num C
NOTES:
1. Depending on the crystal a damping series resistor might be necessary
2. f
3. Maximum value is for extreme cases using high Q, low frequency crystals
4. XCLKS =0 during reset
1a
1b
10
11
12
110
2
3
4
5
6
7
8
9
osc
C Crystal oscillator range (Colpitts)
C Crystal oscillator range (Pierce)
C Oscillator start-up time (Colpitts)
D Clock Quality check time-out
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
P Startup Current
P Clock Monitor Failure Assert Frequency
P External square wave input frequency
= 4MHz, C = 22pF.
DC Operating Bias in Colpitts Configuration on
EXTAL Pin
CMFA.
Rating
Table A-15 Oscillator Characteristics
1(4)
4
CQOUT
UPOSC
specifies the maximum time before switching to the
Symbol
V
t
. The device also features a clock monitor. A
t
UPOSC
CQOUT
f
t
t
t
t
DCBIAS
f
f
i
CMFA
f
EXTH
EXTR
EXTF
EXTL
OSC
C
OSC
OSC
EXT
IN
Min
0.45
100
0.5
0.5
0.5
9.5
9.5
50
Typ
100
1.1
8
7
2
wrs
the CPU starts
Max
100
200
2.5
16
40
50
1
1
3
Unit
MHz
MHz
MHz
KHz
ms
pF
ns
ns
ns
ns
V
s
A