Chapter 8
Security
8.1 Introduction
This device implements security based on the mode selected from the flash module. The
following sections provide an overview of flash security and details the effects of security
on non-flash modules.
8.2 Flash Security
The flash module provides security information to the MCU based on the state held by
the FSEC[SEC] bits. The MCU, in turn, confirms the security request and limits access to
flash resources. During reset, the flash module initializes the FSEC register using data
read from the security byte of the flash configuration field.
NOTE
The security features apply only to external accesses: debug.
CPU accesses to the flash are not affected by the status of
FSEC.
In the unsecured state all flash commands are available on the programming interfaces
either 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 mass
erase operations. Additionally, in this mode, the debug port has no access to memory
locations.
8.3 Security Interactions with other Modules
The flash security settings are used by the system to determine what resources are
available. The following sections describe the interactions between modules and the flash
security settings or the impact that the flash security has on non-flash modules.
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 149
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