MC68HC908GP32 Datasheet, PDF (74/410 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Freescale Semiconductor, Inc.
Resets and Interrupts
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
OSC1
PORRST⁽¹⁾
CGMXCLK
4096
32
32
CYCLES CYCLES CYCLES
CGMOUT
RST PIN
INTERNAL
RESET
1. PORRST is an internally generated power-on reset pulse.
Figure 4-2. Power-On Reset Recovery
Technical Data
72
MC68HC908GP32•MC68HC08GP32 — Rev. 6
Resets and Interrupts
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