Resets and Interrupts
Register Stacking
68HC(9)12DG128 Rev 1.0
MOTOROLA
Resets and Interrupts
129
11-reset
Central Processing
Unit
After reset, the CPU fetches a vector from the appropriate address, then
begins executing instructions. The stack pointer and other CPU registers
are indeterminate immediately after reset. The CCR X and I interrupt
mask bits are set to mask any interrupt requests. The S bit is also set to
inhibit the STOP instruction.
Memory
After reset, the internal register block is located from $0000 to $03FF,
RAM is at $2000 to $3FFF, and EEPROM is located at $0800 to $0FFF.
On the 68HC912DG128, in single chip mode, one 32-Kbyte Flash
module is located from $4000 to $7FFF and $C000 to $FFFF, and the
other three 32-Kbyte Flash modules are accessible through the program
page window located from $8000 to $BFFF. The first 32-Kbyte FLASH
EEPROM is also accessible through the program page window.
On the 68HC12DG128, in single chip mode, one 32-Kbyte ROM module
is located from $4000 to $7FFF and $C000 to $FFFF, and the other
three 32-Kbyte ROM modules are accessible through the program page
window located from $8000 to $BFFF. The first 32-Kbyte ROM is also
accessible through the program page window.
Other Resources
The enhanced capture timer (ECT), pulse width modulation timer
(PWM), serial communications interfaces (SCI0 and SCI1), serial
peripheral interface (SPI), inter-IC bus (IIC), Motorola Scalable CAN
modules (MSCAN0 and MSCAN1) and analog-to-digital converters
(ATD0 and ATD1) are off after reset.
Register Stacking
Once enabled, an interrupt request can be recognized at any time after
the I bit in the CCR is cleared. When an interrupt service request is
recognized, the CPU responds at the completion of the instruction being
executed. Interrupt latency varies according to the number of cycles
required to complete the instruction. Some of the longer instructions can
be interrupted and will resume normally after servicing the interrupt.