M58BW16F, M58BW32F
Block protection
Appendix C
Block protection
OTP protection
The OTP protection is an user-enabled feature that permanently protects specific blocks, so
called “OTP blocks”, against modify operations (program/erase). It is available:
●
on one specific 128-kbit parameter block in the M58BW32F- block 1 (01000h-01FFFh)
for bottom devices or block 72 (FE000h-FEFFFh) for top devices
●
on two specific 64-kbit parameter blocks in the M58BW16F- block 2 and 3 (01000h-
01FFFh) for bottom devices or block 36 and 35 (7E000h-7EFFFh) for top devices.
The default state is unprotected. However, once the protection has been enabled, it is
impossible to disable it and the OTP blocks will remain “modify protected” for ever.
Obviously, this information is stored in internal non volatile registers.
Activation sequence
If the user wants to make the OTP protection effective on a part, he has to issue the Lock
OTP protection command.
The Lock OTP protection requires 2 write cycles:
●
write (ADD=000AAh, DATA=49h) - Lock OTP Protection command 1
●
write (ADD=00003h, DATA=0000 0000h) - Lock OTP Protection command 2
This sequence of commands has to be given with the Tuning Protection unlocked (if this
protection is enabled on the part) and with Write Protect Enable WP_N=’1’. The user can
check its execution polling on the SR in the same way as a normal Program Word
command.
The program duration lasts about 35 µs like for a standard Program Word command. It is
also possible to detect the end of the operation by polling the Status Register.
Any Erase attempt returns A3h in the Status Register while any Program attempt returns
93h.
Once the first write cycle of the Lock OTP protection command is issued, a wrong address
on second write cycle will cause the activation sequence to fail. The Status Register allows
detecting this event and its value is then B1h (invalid sequence).
As a consequence, the protection is not active and the sequence must be restarted.
The Lock OTP Protection command cannot be suspended.
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