Dwt (Data Watchpoint Trigger); Mcu Debug Component (Dbgmcu); Debug Support For Low-Power Modes - STMicroelectronics RM0365 Reference Manual

Debug support (DBG)
33.13

DWT (data watchpoint trigger)

The DWT unit consists of four comparators. They are configurable as:
•
a hardware watchpoint or
• a trigger to an ETM or
•
a PC sampler or
• a data address sampler
The DWT also provides some means to give some profiling informations. For this, some
counters are accessible to give the number of:
•
Clock cycle
•
Folded instructions
•
Load store unit (LSU) operations
•
Sleep cycles
•
CPI (clock per instructions)
•
Interrupt overhead
33.14

MCU debug component (DBGMCU)

The MCU debug component helps the debugger provide support for:
•
Low-power modes
•
Clock control for timers, watchdog, I2C and bxCAN during a breakpoint
•
Control of the trace pins assignment
33.14.1

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 will feed 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 will
enable the internal RC oscillator clock to feed FCLK and HCLK in STOP mode.
1053/1080 DocID025202 Rev 7
RM0365