MC908GR8CDWE Datasheet, PDF (62/408 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Freescale Semiconductor, Inc.
Resets and Interrupts
4.3.2 External Reset
A logic 0 applied to the RST pin for a time, t_IRL, generates an external
reset. An external reset sets the PIN bit in the SIM reset status register.
4.3.3 Internal Reset
Sources:
• Power-on reset (POR)
• Computer operating properly (COP)
• Low-power reset circuits
• Illegal opcode
• Illegal address
All internal reset sources pull the RST pin low for 32 CGMXCLK cycles
to allow resetting of external devices. The MCU is held in reset for an
additional 32 CGMXCLK cycles after releasing the RST pin.
RST PIN
CGMXCLK
INTERNAL
RESET
PULLED LOW BY MCU
32 CYCLES
32 CYCLES
Figure 4-1. Internal Reset Timing
4.3.3.1 Power-On Reset
A power-on reset 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.
Technical Data
62
MC68HC908GR8 — Rev 4.0
Resets and Interrupts
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