ST STM32F301 6 Series Reference Manual page 854

Debug support (DBG)
28.15
Arm® Arm®
The MCU debug component helps the debugger provide support for:
•
Low-power modes
• Clock control for timers, watchdog and I2C during a breakpoint
•
Control of the trace pins assignment
28.15.1 Debug support for low-power modes
To enter low-power mode, the instruction WFI or WFE must be executed.
The MCU implements several low-power modes, which can either deactivate the CPU clock
or reduce the power of the CPU.
The core does not allow FCLK or HCLK to be turned off during a debug session. As these
are required for the debugger connection, during a debug, they must remain active. The
MCU integrates special means to allow the user to debug software in low-power modes.
For this, the debugger host must first set some debug configuration registers to change the
low-power mode behavior:
•
In Sleep mode, DBG_SLEEP bit of DBGMCU_CR register must be previously set by
the debugger. This feeds HCLK with the same clock that is provided to FCLK (system
clock previously configured by the software).
•
In Stop mode, the bit DBG_STOP must be previously set by the debugger. This
enables the internal RC oscillator clock to feed FCLK and HCLK in STOP mode.
28.15.2 Debug support for timers, watchdog I
During a breakpoint, it is necessary to choose how the counter of timers and watchdog
should behave:
• They can continue to count inside a breakpoint. This is usually required when a PWM is
controlling a motor, for example.
•
They can stop to count inside a breakpoint. This is required for watchdog purposes.
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For the I
28.15.3 Debug MCU configuration register
This register allows the configuration of the MCU under DEBUG. This concerns:
•
Low-power mode support
• Timer and watchdog counter support
•
Trace pin assignment
This DBGMCU_CR is mapped on the external PPB bus at address 0xE0042004.
It is asynchronously reset by the PORESET (and not the system reset). It can be written by
the debugger under system reset.
If the debugger host does not support these features, it is still possible for the user software
to write to these registers.
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MCU debug component (DBGMCU)
C, the user can choose to block the SMBUS timeout during a breakpoint.
2
C
RM0366 Rev 5
RM0366