1 Introduction
1.1 Memory Security Module (MSM) Overview
1.2 Unlocking TMS470 Devices With Memory Security
Application Report
SPNA099A – October 2006 – Revised February 2007
Modifying the Memory Security Module Keys
of Catalog TMS470 Devices
John Mangino ..................................................................................................... TMS470 Applications
ABSTRACT
This document shows how to reprogram the Memory Security Module (MSM) keys on
the TMS470 devices. These examples are intended as a reference to enable the user
to modify the MSM keys and unlock the part using the IAR tools. The reference design
includes TMS470 software for use with the IAR Embedded Workbench™.
Contents
1 Introduction .......................................................................................... 1
2 MSM Matching and Modification.................................................................. 2
This application report introduces an understanding of the Memory Security Module (MSM), unlocking the
MSM, and modifying the MSM keys on the TMS470 flash devices. These examples are using the IAR
Embedded Workbench and have information for code generation specific to the IAR tools.
Note: Do not overwrite the flash protection keys and the Memory Security Module (MSM) keys.
If the keys are rewritten and the data is not known, the part cannot be reprogrammed or
accessed in the case of the MSM.
The MSM provides a hardware firewall to prevent unauthorized users from accessing on-chip memories
via the debug/test ports or an external memory interface.
The security modules use a password or key to protect against read and write accesses to protected
memory. The device is secured by its 128-bit password (four 32-bit words). The device is unsecured by
executing the password match flow (PMF) described in the TMS470R1x Memory Security Module
Reference Guide (TI literature number SPNU243).
If code is currently running from inside secure memory, secure code can access secure data. If code is
running from unsecured memory, all read/write accesses to secure memories are blocked. User code can
dynamically jump into and out of secure memory, thereby allowing secure function calls from unsecured
memory. For instance, interrupt service routines can be placed in secure memory, even if the main
program loop is run from unsecured memory.
There are two considerations for unlocking the MSM on TMS470 devices. The first is when the device has
the default keys of 0xFFFFFFFF, and the second is when the keys have been modified.
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SPNA099A – October 2006 – Revised February 2007 Modifying the Memory Security Module Keys of Catalog TMS470 Devices 1
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