Debug Module State In Low Power Modes; Debug & Security - NXP Semiconductors freescale KV4 Series Reference Manual

Table of Contents

With debug enabled, transitions from Run directly to VLPS are not allowed and result in

the system entering Stop mode instead. Status bits within the MDM-AP Status register

can be evaluated to determine this pseudo-VLPS state. Note with the debug enabled,

transitions from Run--> VLPR --> VLPS are still possible but also result in the system

entering Stop mode instead.

In VLLS mode all debug modules are powered off and reset at wakeup.

Going into a VLLSx mode causes all the debug controls and settings to be reset. To give

time to the debugger to sync up with the HW, the MDM-AP Control register can be

configured hold the system in reset on recovery so that the debugger can regain control

and reconfigure debug logic prior to the system exiting reset and resuming operation.

9.10.1 Debug Module State in Low Power Modes

The following table shows the state of the debug modules in low power modes. These

terms are used:

• FF = Full functionality. In VLPR and VLPW the system frequency is limited, but if a

module does not have a limitation in its functionality, it is still listed as FF.

• static = Module register states and associated memories are retained.

• OFF = Modules are powered off; module is in reset state upon wakeup.

Table 9-6. Debug Module State in Low Power Modes

9.11 Debug & Security

When security is enabled (FSEC[SEC] != 10), the debug port capabilities are limited in

order to prevent exploitation of secure data. In the secure state the debugger still has

access to the MDM-AP Status Register and can determine the current security state of the

device. In the case of a secure device, the debugger also has the capability of performing

a mass erase operation via writes to the MDM-AP Control Register. In the case of a

secure device that has mass erase disabled (FSEC[MEEN] = 10), attempts to mass erase

via the debug interface are blocked.

Freescale Semiconductor, Inc.

KV4x Reference Manual, Rev. 2, 02/2015

Chapter 9 Debug