s29cd-j Meet Spansion Inc., s29cd-j Datasheet - Page 45

• Manufacturer Part Number: s29cd-j
• Description: 32/16 Megabit Cmos 2.6 Volt Or 3.3 Volt-only Simultaneous Read/write, Dual Boot, Burst Mode Flash Memory With Versatilei/o?
• Manufacturer: Meet Spansion Inc.

9.5
March 7, 2007 S29CD-J_CL-J_00_B2
Password Protection Method
The Password Protection Method allows an even higher level of security than the Persistent Sector Protection
Mode by requiring a 64-bit password for unlocking the device PPB Lock Bit. In addition to this password
requirement, after power-up and reset, the PPB Lock Bit is set “1” in order to maintain the password mode of
operation. Successful execution of the Password Unlock command by entering the entire password clears the
PPB Lock Bit, allowing for sector PPBs modifications.
Notes
DYB
0
0
0
1
1
0
1
1
4. The DYB Set or Clear commands for the dynamic sector groups signify the protected or
1. There is no special addressing order required for programming the password. Once the password
2. The Password Program Command is only capable of programming “0”s. Programming a “1” after a
3. The password is all “1”s when shipped from the factory.
4. When the password is undergoing programming, Simultaneous Read/Write operation is disabled.
5. All 64-bit password combinations are valid as a password.
6. There is no means to read, program or erase the password is after it is set.
7. The Password Mode Lock Bit, once set, prevents reading the 64-bit password on the data bus and
8. The Password Mode Lock Bit is not erasable.
9. The exact password must be entered in order for the unlocking function to occur.
10. There is a built-in 2-µs delay for each password check. This delay is intended to stop any efforts to
unprotected state of the sector groups respectively. However, if there is a need to change the
status of the persistently locked sector groups, a few more steps are required. First, the PPB Lock
Bit must be cleared by either putting the device through a power-cycle, or hardware reset. The
PPBs can then be changed to reflect the desired settings. Setting the PPB Lock Bit once again
locks the PPBs, and the device operates normally again.
is written and verified, the Password Mode Locking Bit must be set in order to prevent access.
cell is programmed as a “0” results in a time-out with the cell as a “0”. (This is an OTP area).
Read operations to any memory location returns the programming status. Once programming is
complete, the user must issue a Read/Reset command to return the device to normal operation.
further password programming.
run a program that tries all possible combinations in order to crack the password.
PPB
0
0
1
0
1
1
0
1
D a t a
PPB Lock
S h e e t
0
1
0
0
0
1
1
1
S29CD-J & S29CL-J Flash Family
Unprotected—PPB and DYB are changeable
Unprotected—PPB not changeable, DYB is changeable
Protected—PPB and DYB are changeable
Protected—PPB not changeable, DYB is changeable
( P r e l i m i n a r y )
Table 9.1 Sector Protection Schemes
Sector State
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