MC9S12GRMV1 Datasheet, PDF (288/1292 Pages) Freescale Semiconductor, Inc – MC9S12G Family Reference Manual and Data Sheet

Background Debug Module (S12SBDMV1)
• GO_UNTIL command
• Hardware handshake protocol to increase the performance of the serial communication
• Active out of reset in special single chip mode
• Nine hardware commands using free cycles, if available, for minimal CPU intervention
• Hardware commands not requiring active BDM
• 14 firmware commands execute from the standard BDM firmware lookup table
• Software control of BDM operation during wait mode
• When secured, hardware commands are allowed to access the register space in special single chip
mode, if the Flash erase tests fail.
• Family ID readable from BDM ROM at global address 0x3_FF0F in active BDM
(value for devices with HCS12S core is 0xC2)
• BDM hardware commands are operational until system stop mode is entered
7.1.2 Modes of Operation
BDM is available in all operating modes but must be enabled before firmware commands are executed.
Some systems may have a control bit that allows suspending the function during background debug mode.
7.1.2.1 Regular Run Modes
All of these operations refer to the part in run mode and not being secured. The BDM does not provide
controls to conserve power during run mode.
• Normal modes
General operation of the BDM is available and operates the same in all normal modes.
• Special single chip mode
In special single chip mode, background operation is enabled and active out of reset. This allows
programming a system with blank memory.
7.1.2.2 Secure Mode Operation
If the device is in secure mode, the operation of the BDM is reduced to a small subset of its regular run
mode operation. Secure operation prevents access to Flash other than allowing erasure. For more
information please see Section 7.4.1, “Security”.
7.1.2.3 Low-Power Modes
The BDM can be used until stop mode is entered. When CPU is in wait mode all BDM firmware
commands as well as the hardware BACKGROUND command cannot be used and are ignored. In this case
the CPU can not enter BDM active mode, and only hardware read and write commands are available. Also
the CPU can not enter a low power mode (stop or wait) during BDM active mode.
In stop mode the BDM clocks are stopped. When BDM clocks are disabled and stop mode is exited, the
BDM clocks will restart and BDM will have a soft reset (clearing the instruction register, any command in
progress and disable the ACK function). The BDM is now ready to receive a new command.
MC9S12G Family Reference Manual, Rev.1.23
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Freescale Semiconductor