Datasheet

Monitor ROM (MON)
Technical Data MC68HC908LJ12 — Rev. 2.1
162 Monitor ROM (MON) Freescale Semiconductor
Figure 10-2. Low-Voltage Monitor Mode Entry Flowchart
In monitor mode, the MCU uses different vectors for reset, SWI
(software interrupt), and break interrupt than those for user mode. The
alternate vectors are in the $FE page instead of the $FF page and allow
code execution from the internal monitor firmware instead of user code.
NOTE: Exiting monitor mode after it has been initiated by having a blank reset
vector requires a power-on reset (POR). Pulling RST low will not exit
monitor mode in this situation.
Table 10-2 summarizes the differences between user mode and monitor
mode vectors.
IS VECTOR
BLANK?
POR
TRIGGERED?
NORMAL USER
MODE
MONITOR MODE
EXECUTE
MONITOR
CODE
NO
NO
YES
YES
POR RESET
Table 10-2. Mode Differences (Vectors)
Modes
Functions
Reset
Vector
High
Reset
Vector
Low
Break
Vector
High
Break
Vector
Low
SWI
Vector
High
SWI
Vector
Low
User $FFFE $FFFF $FFFC $FFFD $FFFC $FFFD
Monitor $FEFE $FEFF $FEFC $FEFD $FEFC $FEFD