mc68hc912dg128 Freescale Semiconductor, Inc, mc68hc912dg128 Datasheet - Page 142

• Manufacturer Part Number: mc68hc912dg128
• Description: M68hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Resets and Interrupts
9.8 Effects of Reset
9.8.1 Operating Mode and Memory Map
9.8.2 Clock and Watchdog Control Logic
9.8.3 Interrupts
9.8.4 Parallel I/O
Technical Data
142
When a reset occurs, MCU registers and control bits are changed to
known start-up states, as follows.
Operating mode and default memory mapping are determined by the
states of the BKGD, MODA, and MODB pins during reset. The SMODN,
MODA, and MODB bits in the MODE register reflect the status of the
mode-select inputs at the rising edge of reset. Operating mode and
default maps can subsequently be changed according to strictly defined
rules.
The COP watchdog system is enabled, with the CR[2:0] bits set for the
longest duration time-out. The clock monitor is disabled. The RTIF flag
is cleared and automatic hardware interrupts are masked. The rate
control bits are cleared, and must be initialized before the RTI system is
used. The DLY control bit is set to specify an oscillator start-up delay
upon recovery from STOP mode.
PSEL is initialized in the HPRIO register with the value $F2, causing the
external IRQ pin to have the highest I-bit interrupt priority. The IRQ pin
is configured for level-sensitive operation (for wired-OR systems).
However, the interrupt mask bits in the CPU12 CCR are set to mask X-
and I-related interrupt requests.
If the MCU comes out of reset in a single-chip mode, all ports are
configured as general-purpose high-impedance inputs.
Freescale Semiconductor, Inc.
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Resets and Interrupts
MC68HC912DG128 — Rev 3.0
MOTOROLA