S70GL01GN00 Datasheet, PDF (33/83 Pages) SPANSION – 3.0 Volt-only Page Mode Flash Memory featuring 110 nm MirrorBit™ Process Technology

Advance Information
namic states because it is very easy to switch back and forth between the
protected and un-protected conditions. This allows software to easily protect sec-
tors against inadvertent changes yet does not prevent the easy removal of
protection when changes are needed.
The DYB bits maybe set or cleared as often as needed. The PPB bits allow for a
more static, and difficult to change, level of protection. The PPB bits retain their
state across power cycles because they are Non-Volatile. Individual PPB bits are
set with a program command but must all be cleared as a group through an erase
command.
The PPB Lock Bit adds an additional level of protection. Once all PPB bits are pro-
grammed to the desired settings, the PPB Lock Bit may be set to the freeze state.
Setting the PPB Lock Bit to the freeze state disables all program and erase com-
mands to the Non-Volatile PPB bits. In effect, the PPB Lock Bit locks the PPB bits
into their current state. The only way to clear the PPB Lock Bit to the unfreeze
state is to go through a power cycle, or hardware reset. The Software Reset com-
mand does not clear the PPB Lock Bit to the unfreeze state. System boot code
can determine if any changes to the PPB bits are needed e.g. to allow new system
code to be downloaded. If no changes are needed then the boot code can set the
PPB Lock Bit to disable any further changes to the PPB bits during system
operation.
The WP# write protect pin adds a final level of hardware protection. When this
pin is low it is not possible to change the contents of the WP# protected sectors.
These sectors generally hold system boot code. So, the WP# pin can prevent any
changes to the boot code that could override the choices made while setting up
sector protection during system initialization.
It is possible to have sectors that are 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 Set command sequence is
all that is necessary. The DYB Set and DYB Clear commands for the dynamic sec-
tors switch the DYB bits 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 to the unfreeze state
by either putting the device through a power-cycle, or hardware reset. The PPB
bits can then be changed to reflect the desired settings. Setting the PPB Lock Bit
once again to the freeze state locks the PPB bits, and the device operates nor-
mally again.
Note: to achieve the best protection, it is recommended to execute the PPB Lock
Bit Set command early in the boot code, and protect the boot code by holding
WP# = V_IL.
Persistent Protection Bit (PPB)
A single Persistent (non-volatile) Protection Bit is assigned to each sector. If a PPB
is programmed to the protected state through the PPB Program command, that
sector is protected from program or erase operations is read-only. If a PPB re-
quires erasure, all of the sector PPB bits must first be erased in parallel through
the All PPB Erase command. The All PPB Erase command preprograms all PPB bits
prior to PPB erasing. All PPB bits erase in parallel, unlike programming where in-
dividual PPB bits are programmable. The PPB bits have the same endurance as
the flash memory.
Programming the PPB bit requires the typical word programming time without uti-
lizing the Write Buffer. During a PPB bit programming and A11 PPB bit erasing
June 1, 2005 S70GL01GN00_00_A1
S70GL01GN00 MirrorBit^TM Flash
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