MC3S12RG128 Datasheet, PDF (525/546 Pages) Freescale Semiconductor, Inc – Microcontrollers

Appendix A Electrical Characteristics
A.6.1.4 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.6.1.5 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_wrs the CPU starts
fetching the interrupt vector.
A.6.2 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_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-17. 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)
1b C Crystal oscillator range (Pierce) ¹
f_OSC
0.5
f_OSC
0.5
16
MHz
40
MHz
2 P Startup Current
3 C Oscillator start-up time (Colpitts)
i_OSC
100
t_UPOSC
µA
8²
100³
ms
4 D Clock Quality check time-out
t_CQOUT
0.45
2.5
s
5 P Clock Monitor Failure Assert Frequency
6 P External square wave input frequency ⁴
f_CMFA
50
100
200
KHz
f_EXT
0.5
66
MHz
7 D External square wave pulse width low
t_EXTL
7.2
ns
8 D External square wave pulse width high
t_EXTH
7.2
ns
9 D External square wave rise time
t_EXTR
1
ns
10 D External square wave fall time
t_EXTF
1
ns
11 D Input Capacitance (EXTAL, XTAL pins)
C_IN
7
pF
12 C DC Operating Bias in Colpitts Configuration on
V_DCBIAS
1.1
V
EXTAL Pin
1 _{Depending on the crystal a damping series resistor might be necessary}
2 _{fosc = 4MHz, C = 22pF.}
3 _{Maximum value is for extreme cases using high Q, low frequency crystals}
MC3S12RG128 Data Sheet, Rev. 1.05
Freescale Semiconductor
525