2.3 Incorporating Code Security in User Applications
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Incorporating Code Security in User Applications
Code security is typically not required in the development phase of a project; however, security is needed
once a robust code is developed. Before such a code is programmed in the flash memory, a password
should be chosen to secure the device. Once a password is in place, the device is secured (i.e.,
programming a password at the appropriate locations and either performing a device reset or setting the
FORCESEC bit (CSMSCR.15) is the action that secures the device). From that time on, access to debug
the contents of secure memory by any means (via JTAG, code running off external/on-chip memory etc.)
requires the supply of a valid password. A password is not needed to run the code out of secure memory
(such as in a typical end-customer usage); however, access to secure memory contents for debug
purpose requires a password.
Table 2-4. Code Security Module (CSM) Registers
Memory
Address Register Name Reset Values Register Description
KEY Registers
0x00 - 0AE0 KEY0
(1)
0xFFFF Low word of the 128-bit KEY register
0x00 - 0AE1 KEY1
(1)
0xFFFF Second word of the 128-bit KEY register
0x00 - 0AE2 KEY2
(1)
0xFFFF Third word of the 128-bit KEY register
0x00 - 0AE3 KEY3
(1)
0xFFFF Fourth word of the 128-bit key
0x00 - 0AE4 KEY4
(1)
0xFFFF Fifth word of the 128-bit key
0x00 - 0AE5 KEY5
(1)
0xFFFF Sixth word of the 128-bit key
0x00 - 0AE6 KEY6
(1)
0xFFFF Seventh word of the 128-bit key
0x00 - 0AE7 KEY7
(1)
0xFFFF High word of the 128-bit KEY register
0x00 - 0AEF CSMSCR
(1)
0x005F CSM status and control register
Password Locations (PWL) in Flash Memory - Reserved for the CSM password only
0x33 - FFF8 PWL0 User defined Low word of the 128-bit password
0x33 - FFF9 PWL1 User defined Second word of the 128-bit password
0x33 - FFFA PWL2 User defined Third word of the 128-bit password
0x33 - FFFB PWL3 User defined Fourth word of the 128-bit password
0x33 - FFFC PWL4 User defined Fifth word of the 128-bit password
0x33 - FFFD PWL5 User defined Sixth word of the 128-bit password
0x33 - FFFE PWL6 User defined Seventh word of the 128-bit password
0x33 - FFFF PWL7 User defined High word of the 128-bit password
(1)
These registers are EALLOW protected. Refer to Section 5.2 for more information.
SPRUFB0C – September 2007 – Revised May 2009 Code Security Module (CSM) 31
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