Motorola MC9S12DB128B Low Power Modes, Unsecuring the Microcontroller, Pseudo Stop, Wait

MC9S12DT128B Device User Guide — V01.07

4.3.3 Unsecuring the Microcontroller

In order to unsecure the microcontroller, the internal FLASH and EEPROM must be erased. This can be done through an external program in expanded mode.

Once the user has erased the FLASH and EEPROM, the part can be reset into special single chip mode. This invokes a program that verifies the erasure of the internal FLASH and EEPROM. Once this program completes, the user can erase and program the FLASH security bits to the unsecured state. This is generally done through the BDM, but the user could also change to expanded mode (by writing the mode bits through the BDM) and jumping to an external program (again through BDM commands). Note that if the part goes through a reset before the security bits are reprogrammed to the unsecure state, the part will be secured again.

4.4 Low Power Modes

The microcontroller features three main low power modes. Consult the respective Block User Guide for information on the module behavior in Stop, Pseudo Stop, and Wait Mode. An important source of information about the clock system is the Clock and Reset Generator User Guide (CRG).

4.4.1 Stop

Executing the CPU STOP instruction stops all clocks and the oscillator thus putting the chip in fully static mode. Wake up from this mode can be done via reset or external interrupts.

4.4.2 Pseudo Stop

This mode is entered by executing the CPU STOP instruction. In this mode the oscillator is still running and the Real Time Interrupt (RTI) or Watchdog (COP) sub module can stay active. Other peripherals are turned off. This mode consumes more current than the full STOP mode, but the wake up time from this mode is significantly shorter.

4.4.3 Wait

This mode is entered by executing the CPU WAI instruction. In this mode the CPU will not execute instructions. The internal CPU signals (address and databus) will be fully static. All peripherals stay active. For further power consumption the peripherals can individually turn off their local clocks.

4.4.4 Run

Although this is not a low power mode, unused peripheral modules should not be enabled in order to save power.

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