Resets and Interrupts
Technical Data
MC68HC908GP32
•
MC68HC08GP32
—
Rev. 6
72
Resets and Interrupts
MOTOROLA
4.3.3.1 Power-On Reset
A power-on reset (POR) is an internal reset caused by a positive
transition on the V
DD
pin. V
DD
at the POR must go completely to 0 V to
reset the MCU. This distinguishes between a reset and a POR. The POR
is not a brown-out detector, low-voltage detector, or glitch detector.
A power-on reset:
•
Holds the clocks to the CPU and modules inactive for an oscillator
stabilization delay of 4096 CGMXCLK cycles
•
Drives the RST pin low during the oscillator stabilization delay
•
Releases the RST pin 32 CGMXCLK cycles after the oscillator
stabilization delay
•
Releases the CPU to begin the reset vector sequence 64
CGMXCLK cycles after the oscillator stabilization delay
•
Sets the POR and LP bits in the SIM reset status register and
clears all other bits in the register
Figure 4-2. Power-On Reset Recovery
PORRST
(1)
OSC1
CGMXCLK
CGMOUT
RST PIN
INTERNAL
4096
CYCLES
32
CYCLES
32
CYCLES
1. PORRST is an internally generated power-on reset pulse.
RESET
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Freescale Semiconductor, Inc.
For More Information On This Product,
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