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Appendix A Electrical Characteristics
MC9S12XF - Family Reference Manual, Rev.1.19
Freescale Semiconductor
1213
A.6
Reset, Oscillator and PLL
This section summarizes the electrical characteristics of the various startup scenarios for oscillator and
phase-locked loop (PLL).
A.6.1
Startup
Table A-20 summarizes several startup characteristics explained in this section. Detailed description of the
startup behavior can be found in the Clock and Reset Generator (CRG) block description
A.6.1.1
POR
The release level VPORR and the assert level VPORA are derived from the VDD supply. They are also valid
if the device is powered externally. After releasing the POR reset the oscillator and the clock quality check
are started. If after a time tCQOUT no valid oscillation is detected, the MCU will start using the internal self
clock. The fastest startup time possible is given by nuposc.
A.6.1.2
SRAM Data Retention
Provided an appropriate external reset signal is applied to the MCU, preventing the CPU from executing
code when VDD35 is out of specication limits, the SRAM contents integrity is guaranteed if after the reset
the PORF bit in the CRG ags register has not been set.
A.6.1.3
External Reset
When external reset is asserted for a time greater than PWRSTL the CRG module generates an internal
reset, and the CPU starts fetching the reset vector without doing a clock quality check, if there was an
oscillation before reset.
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.
If the MCU is woken-up by an interrupt and the fast wake-up feature is enabled (FSTWKP = 1 and
SCME = 1), the system will resume operation in self-clock mode after tfws.
Table A-20. Startup Characteristics
Num
C
Rating
Symbol
Min
Typ
Max
Unit
1
D Reset input pulse width, minimum input time
PWRSTL
2—
—
tosc
2
D Startup from reset
tRST
96
—
4000(1)
1. This is the time between RESET deassertion and start of CPU code execution.
nbus
3
D Wait recovery startup time
tWRS
—
14
tcyc
4
D Fast wakeup from STOP(2)
2. Including voltage regulator startup; VDD /VDDF lter capacitors 220 nF, VDD35 = 5 V, T= 25°C
tfws
—
50
100
s