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Chapter 1 Device Overview MC9S12ZVM-Family
MC9S12ZVM Family Reference Manual Rev. 1.3
Freescale Semiconductor
49
1.9
Modes of Operation
The MCU can operate in different modes. These are described in
1.9.1 Chip Configuration Modes
The MCU can operate in different power modes to facilitate power saving when full system performance
is not required. These are described in
Some modules feature a software programmable option to freeze the module status whilst the background
debug module is active to facilitate debugging. This is referred to as freeze mode at module level.
1.9.1
Chip Configuration Modes
The different modes and the security state of the MCU affect the debug features (enabled or disabled).
The operating mode out of reset is determined by the state of the MODC signal during reset (
).
The MODC bit in the MODE register shows the current operating mode and provides limited mode
switching during operation. The state of the MODC signal is latched into this bit on the rising edge of
RESET.
1.9.1.1
Normal Single-Chip Mode
This mode is intended for normal device operation. The opcode from the on-chip memory is being
executed after reset (requires the reset vector to be programmed correctly). The processor program is
executed from internal memory.
1.9.1.2
Special Single-Chip Mode
This mode is used for debugging operation, boot-strapping, or security related operations. The background
debug mode (BDM) is active on leaving reset in this mode.
1.9.2
Debugging Modes
The background debug mode (BDM) can be activated by the BDC module or directly when resetting into
Special Single-Chip mode. Detailed information can be found in the BDC module section.
Writing to internal memory locations using the debugger, whilst code is running or at a breakpoint, can
change the flow of application code.
The MC9S12ZVM-Family supports BDC communication throughout the device Stop mode. During Stop
mode, writes to control registers can alter the operation and lead to unexpected results. It is thus
recommended not to reconfigure the peripherals during STOP using the debugger.
Table 1-10. Chip Modes
Chip Modes
MODC
Normal single chip
1
Special single chip
0