NXP Semiconductors freescale K51 Series Reference Manual

8.3 Security Interactions with other ModulesThe flash security settings are used by the SoC to determine what resources are available.The following sections describe the interactions between modules and the flash securitysettings or the impact that the flash security has on non-flash modules.8.3.1 Security Interactions with EzPortWhen flash security is active the MCU can still boot in EzPort mode. The EzPort holdsthe flash logic in NVM special mode and thus limits flash operation when flash securityis active. While in EzPort mode and security is active, flash bulk erase (BE) can still beexecuted. The write FCCOB registers (WRFCCOB) command is limited to the masserase (Erase All Blocks) and verify all 1s (Read 1s All Blocks) commands. Read accessesto internal memories via the EzPort are blocked when security is enabled.The mass erase can be used to disable flash security, but all of the flash contents are lostin the process. A mass erase via the EzPort is allowed even when some memory locationsare protected.When mass erase has been disabled, mass erase via the EzPort is blocked and cannot bedefeated.8.3.2 Security Interactions with DebugWhen flash security is active the JTAG port cannot access the memory resources of theMCU. Boundary scan chain operations work, but debugging capabilities are disabled sothat the debug port cannot read flash contents.Although most debug functions are disabled, the debugger can write to the Flash MassErase in Progress bit in the MDM-AP Control register to trigger a mass erase (Erase AllBlocks) command. A mass erase via the debugger is allowed even when some memorylocations are protected.When mass erase is disabled, mass erase via the debugger is blocked.Security Interactions with other ModulesK51 Sub-Family Reference Manual, Rev. 6, Nov 2011202 Freescale Semiconductor, Inc.