• all system clocks, except the core clock, are disabled,
• the debug module has access to core registers, and
• access to the on-chip peripherals is blocked.
No debug is available while the MCU is in VLLS modes.
Entering into a VLLS mode causes all of the debug controls and settings to be powered
off. To give time to the debugger to sync with the MCU, the MDM AP Control Register
includes a Very-Low-Leakage Debug Request (VLLDBGREQ) bit that is set to configure
the Reset Controller logic to hold the system in reset after the next recovery from a VLLS
mode. This bit allows the debugger time to reinitialize the debug module before the
debug session continues.
The MDM AP Control Register also includes a Very Low Leakage Debug Acknowledge
(VLLDBGACK) bit that is set to release the ARM core being held in reset following a
VLLS recovery. The debugger reinitializes all debug IP, and then asserts the
VLLDBGACK control bit to allow the RCM to release the ARM core from reset and
allow CPU operation to begin.
The VLLDBGACK bit is cleared by the debugger (or can be left set as is) or clears
automatically due to the reset generated as part of the next VLLS recovery.
Functional description
KL02 Sub-Family Reference Manual, Rev. 2.1, July 2013
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Freescale Semiconductor, Inc.