284 CHAPTER 9 Low Power Debugging
J-Link / J-Trace (UM08001) ©
2004-2017 SEGGER Microcontroller GmbH & Co. KG
9.3 Restrictions
As the connection to the target is temporary lost while it is in low power mode, some
restrictions during debug apply:
• Make sure that the IDE does not perform periodic accesses to memory while the
target is in a low power mode. E.g.: Disable periodic refresh of memory windows,
close live watch windows etc.
• Avoid issuing manual halt requests to the target while it is in a low power mode.
• Do not try to set breakpoints while the target already is in a low power mode. If
a breakpoint in a wake-up routine shall be hit as soon as the target wakes up
from low power mode, set this breakpoint before the target enters low power
mode.
• Single stepping instructions that enter a low power mode (e.g. WFI/WFE on Cor-
tex-M) is not possible/supported.
• Debugging low power modes that require a reset to wake-up can only be
debugged on targets where the debug interface is not reset by such a reset. Oth-
erwise breakpoints and other settings are lost which may result in unpredictable
behavior.
J-Link does it’s best to handle cases where one or more of the above restrictions is
not considered but depending on how the IDE reacts to specific operations to fail,
error messages may appear or the debug session will be terminated by the IDE.
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