Monitor ROM (MON)
Functional Description
MC68HC908GP32
•
MC68HC08GP32
—
Rev. 6
Technical Data
MOTOROLA
Monitor ROM (MON)
201
Figure 15-2. Low-Voltage Monitor Mode Entry Flowchart
Enter monitor mode with pin configuration shown in
Figure 15-1
by
pulling RST low and then high. The rising edge of RST latches monitor
mode. Once monitor mode is latched, the values on the specified pins
can change.
Once out of reset, the MCU waits for the host to send eight security
bytes. (See
15.5 Security
.) After the security bytes, the MCU sends a
break signal (10 consecutive logic 0s) to the host, indicating that it is
ready to receive a command.
NOTE:
The PTA7 pin must remain at logic 0 for 24 bus cycles after the RST pin
goes high to enter monitor mode properly.
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.
IS VECTOR
BLANK?
POR
TRIGGERED?
NORMAL USER
MODE
MONITOR MODE
EXECUTE
MONITOR
CODE
NO
NO
YES
YES
POR RESET
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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