mc68hc908ap8a Freescale Semiconductor, Inc, mc68hc908ap8a Datasheet - Page 119

• Manufacturer Part Number: mc68hc908ap8a
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

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.
Table 8-2
8.3.2 Data Format
Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format.
Transmit and receive baud rates must be identical.
Freescale Semiconductor
summarizes the differences between user mode and monitor mode vectors.
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.
START
BIT
Monitor
Modes
User
Figure 8-2. Low-Voltage Monitor Mode Entry Flowchart
BIT 0
BIT 1
Table 8-2. Mode Differences (Vectors)
Vector
$FFFE
$FEFE
Reset
High
MC68HC908AP A-Family Data Sheet, Rev. 3
Figure 8-3. Monitor Data Format
BIT 2
MONITOR MODE
TRIGGERED?
POR RESET
IS VECTOR
EXECUTE
MONITOR
BLANK?
BIT 3
CODE
Vector
POR
$FFFF
$FEFF
Reset
Low
YES
YES
BIT 4
NOTE
NO
NO
$FEFC
Vector
$FFFC
Break
High
BIT 5
Functions
NORMAL USER
BIT 6
Vector
$FFFD
$FEFD
Break
Low
MODE
BIT 7
$FEFC
Vector
$FFFC
STOP
High
SWI
BIT
START
NEXT
BIT
Vector
$FFFD
$FEFD
Functional Description
Low
SWI
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