MC68HC908JL3E Datasheet, PDF (112/226 Pages) Motorola, Inc – Microcontrollers

Monitor ROM (MON)
POR RESET
IS VECTOR
NO
BLANK?
YES
MONITOR MODE
EXECUTE
MONITOR
CODE
NORMAL USER
MODE
POR
NO
TRIGGERED?
YES
Figure 9-2. Low-Voltage Monitor Mode Entry Flowchart
Enter monitor mode with the pin configuration shown above 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 9.5 Security.) After the security bytes, the MCU sends a
break signal (10 consecutive logic zeros) to the host, indicating that it is
ready to receive a command. The break signal also provides a timing
reference to allow the host to determine the necessary baud rate.
In monitor mode, the MCU uses different vectors for reset, SWI, and
break interrupt. 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.
Technical Data
112
MC68H(R)C908JL3E/JK3E/JK1E — Rev. 2.0
Monitor ROM (MON)
MOTOROLA