MC9S12B128 Datasheet, PDF (107/128 Pages) Motorola, Inc – microcontroller unit (MCU)

Device User Guide —9S12B128DGV1/D V01.11
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. 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-20 Oscillator Characteristics
Conditions are shown in Table A-4 unless otherwise noted
Num C
Rating
Symbol
Min
1a C Crystal oscillator range (Colpitts)
f_OSC
0.5
1b C _{Crystal oscillator range (Pierce)} ¹
f_OSC
0.5
2 P Startup Current
i_OSC
100
3 C Oscillator start-up time (Colpitts)
t_UPOSC
4 D Clock Quality check time-out
t_CQOUT
0.45
5 P Clock Monitor Failure Assert Frequency
f_CMFA
50
6 P _{External square wave input frequency} ⁴
f_EXT
0.5
7 D _{External square wave pulse width low} ⁴
t_EXTL
9.5
8 D _{External square wave pulse width high}⁴
t_EXTH
9.5
9 D _{External square wave rise time}⁴
t_EXTR
10 D _{External square wave fall time}⁴
t_EXTF
11 D Input Capacitance (EXTAL, XTAL pins)
C_IN
12
C
DC Operating Bias in Colpitts Configuration on
EXTAL Pin
V_DCBIAS
13 P _{EXTAL Pin Input High Voltage}⁴
V_IH,EXTAL 0.75*V_DDPLL
T _{EXTAL Pin Input High Voltage}⁴
V_IH,EXTAL
14 P _{EXTAL Pin Input Low Voltage}⁴
V_IL,EXTAL
T _{EXTAL Pin Input Low Voltage}⁴
V_IL,EXTAL V_SSPLL - 0.3
15 C _{EXTAL Pin Input Hysteresis}⁴
V_HYS,EXTAL
NOTES:
1. Depending on the crystal a damping series resistor might be necessary
2. f_osc = 4MHz, C = 22pF.
3. Maximum value is for extreme cases using high Q, low frequency crystals
4. Only valid if Pierce oscillator/external clock mode is selected
Typ
8²
100
7
1.1
250
Max
16
40
100³
2.5
200
50
1
1
Unit
MHz
MHz
µA
ms
s
KHz
MHz
ns
ns
ns
ns
pF
V
V
V_DDPLL + 0.3 V
0.25*V_DDPLL V
V
mV
107