Chapter 8Security8.1 IntroductionThis device implements security based on the mode selected from the flash module. Thefollowing sections provide an overview of flash security and details the effects of securityon non-flash modules.8.2 Flash SecurityThe flash module provides security information to the MCU based on the state held bythe FSEC[SEC] bits. The MCU, in turn, confirms the security request and limits access toflash resources. During reset, the flash module initializes the FSEC register using dataread from the security byte of the flash configuration field.NOTEThe security features apply only to external accesses: debug.CPU accesses to the flash are not affected by the status ofFSEC.In the unsecured state all flash commands are available on the programming interfaceseither from the debug port (SWD) or user code execution. When the flash is secured(FSEC[SEC] = 00, 01, or 11), the programmer interfaces are only allowed to launch masserase operations. Additionally, in this mode, the debug port has no access to memorylocations.8.3 Security Interactions with other ModulesThe flash security settings are used by the system to determine what resources areavailable. The following sections describe the interactions between modules and the flashsecurity settings or the impact that the flash security has on non-flash modules.KL25 Sub-Family Reference Manual, Rev. 3, September 2012Freescale Semiconductor, Inc. 149
