MC68HC908GR8 Datasheet, PDF (135/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

POR RESET
Functional Description
IS VECTOR ^NO
BLANK?
YES
MONITOR MODE
NORMAL USER
MODE
EXECUTE
MONITOR
CODE
POR
NO
TRIGGERED?
YES
Figure 15-2. 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. Pulling RST low will not exit monitor mode
in this situation.
Table 15-2 summarizes the differences between user mode and monitor mode.
Table 15-2. Mode Differences
Modes
User
Monitor
Reset
Vector
High
$FFFE
$FEFE
Reset
Vector
Low
$FFFF
$FEFF
Functions
Break
Vector
High
Break
Vector
Low
$FFFC $FFFD
$FEFC $FEFD
SWI
Vector
High
$FFFC
$FEFC
SWI
Vector
Low
$FFFD
$FEFD
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
Freescale Semiconductor
135