S29PL-J55BAI011 datasheet(48/96 Pages) SPANSION

48 / 96 page

S29PL-J

S29PL-J_00_A9 September 22, 2006

Data

Sheet

(Adv an ce

Inf o r m a t io n)

The WP#/ACC write protect pin adds a final level of hardware protection to sectors SA1-133, SA1-134, SA2-

0 and SA2-1. When this pin is low it is not possible to change the contents of these sectors. These sectors

generally hold system boot code. The WP#/ACC pin can prevent any changes to the boot code that could

override the choices made while setting up sector protection during system initialization.

For customers who are concerned about malicious viruses there is another level of security - the persistently

locked state. To persistently protect a given sector or sector group, the PPBs associated with that sector need

to be set to “1”. Once all PPBs are programmed to the desired settings, the PPB Lock should be set to “1”.

Setting the PPB Lock automatically disables all program and erase commands to the Non-Volatile PPBs. In

effect, the PPB Lock “freezes” the PPBs into their current state. The only way to clear the PPB Lock is to go

through a power cycle.

It is possible to have sectors that have been persistently locked, and sectors that are left in the dynamic state.

The sectors in the dynamic state are all unprotected. If there is a need to protect some of them, a simple DYB

Write command sequence is all that is necessary. The DYB write command for the dynamic sectors switch

the DYBs to signify protected and unprotected, respectively. If there is a need to change the status of the

persistently locked sectors, a few more steps are required. First, the PPB Lock bit must be disabled 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 will lock the PPBs, and the device operates normally

again.

The best protection is achieved by executing the PPB lock bit set command early in the boot code, and

protect the boot code by holding WP#/ACC = VIL.

Table 17 contains all possible combinations of the DYB, PPB, and PPB lock relating to the status of the

sector.

In summary, if the PPB is set, and the PPB lock is set, the sector is protected and the protection can not be

removed until the next power cycle clears the PPB lock. If the PPB is cleared, the sector can be dynamically

locked or unlocked. The DYB then controls whether or not the sector is protected or unprotected.

If the user attempts to program or erase a protected sector, the device ignores the command and returns to

read mode. A program command to a protected sector enables status polling for approximately 1 µs before

the device returns to read mode without having modified the contents of the protected sector. An erase

command to a protected sector enables status polling for approximately 50 µs after which the device returns

to read mode without having erased the protected sector.

The programming of the DYB, PPB, and PPB lock for a given sector can be verified by writing a DYB/PPB/

PPB lock verify command to the device. There is an alternative means of reading the protection status. Take

RESET# to VIL and hold WE# at VIH. (The high voltage A9 Autoselect Mode also works for reading the status

of the PPBs). Scanning the addresses (A18–A11) while (A6, A1, A0) = (0, 1, 0) will produce a logical ‘1” code

at device output DQ0 for a protected sector or a “0” for an unprotected sector. In this mode, the other

addresses are don’t cares. Address location with A1 = VIL are reserved for autoselect manufacturer and

device codes.

12.4

Persistent Sector Protection Mode Locking Bit

Like the password mode locking bit, a Persistent Sector Protection mode locking bit exists to guarantee that

the device remain in software sector protection. Once set, the Persistent Sector Protection locking bit

prevents programming of the password protection mode locking bit. This guarantees that a hacker could not

place the device in password protection mode.

S29PL-J55BAI011 Datasheet(PDF) 48 Page - SPANSION

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