2.3.2 Password Match Flow
Start
Yes
No
Yes
No
Deviceî˜ unsecure
Userî˜ canî˜ access
on-chipî˜ secure
memory
Deviceî˜ permanentlyî˜ secured
CPUî˜ accessî˜ isî˜ limited.
Deviceî˜ cannotî˜ beî˜ debugged
orî˜ reprogrammed.
Doî˜ dummyî˜ readî˜ ofî˜ PWL
0x33î˜ FFF8 − 0x33î˜ FFFF
KEYî˜ registersî˜ =î˜ allî˜ ones
Correct
password?
Areî˜ PWLî˜ =
allî˜ Fs?
Areî˜ PWLî˜ =
allî˜ zeros?
Deviceî˜ secureî˜ after
resetî˜ orî˜ runtime
No
Yes
Writeî˜ theî˜ passwordî˜ to
KEYî˜ registers
0x00î˜ 0AE0 0x00î˜ 0AE7
(A)
−
www.ti.com
Incorporating Code Security in User Applications
Password match flow (PMF) is essentially a sequence of eight dummy reads from password locations
(PWL) followed by eight writes to KEY registers.
Figure 2-2 shows how the PMF helps to initialize the security logic registers and disable security logic.
Figure 2-2. Password Match Flow (PMF)
A The KEY registers are EALLOW protected.
SPRUFB0C – September 2007 – Revised May 2009 Code Security Module (CSM) 33
Submit Documentation Feedback