W29GL032C_13 Datasheet, PDF (23/68 Pages) Winbond – 32M-BIT 3.0-VOLT PARALLEL FLASH MEMORY WITH PAGE MODE

W29GL032C
7.3.2 Individual (Non-Volatile) Protection Mode
7.3.2.1 Individual Protection Bits (IPB)
The Individual Protection Bit (IPB) is a nonvolatile bit, one bit per sector, with endurance equal to that
of the Flash memory array. Before erasing, IPB preprogramming and verification is managed by the
device, so no monitoring is necessary.
The Individual Protection Bits are set sector by sector by the IPB program instruction. Once a IPB is
set to “0”, the linked sector is protected, blocking any program and/or erase functions on that sector.
The IPB cannot be erased individually, but executing the “All IPB Erase” instruction will erase all IPB
simultaneously. Read and write functions are disabled when IPB programming is going on for all
sectors until this mode exits.
In case one of the protected sectors need to be unprotected, first, the IPB Lock Bit must be set to “1”
by performing one of the following: power-cycle the device or perform a hardware reset. Second, an
“All IPB Erase instruction needs to be performed. Third, Individual Protection Bits need to be set once
again to reflect the desired settings and finally, the IPB Lock Bit needs to be set once again which
locks the Individual Protection Bits and the device functions normally once again.
Executing an IPB Read instruction to the device is required to verify the programming state of the IPB
for any given sector. Refer to the IPB Program Algorithm flow chart below for details.
Note that
• While IPB Lock Bit is set, Program and/or erase instructions will not be executed and times
out without programming and/or erasing the IPB.
• For best protection results, it is recommended to execute the IPB Lock Bit Set instruction early
on in the boot code. Also, protect the boot code by holding #WP/ACC = VIL. Note that the IPB
and DPB bits perform the same when #WP/ACC = VHH, and when #WP/ACC =VIH.
• While in the IPB command mode, read within that sector will bring the IPB status back for that
sector. All Read must be executed by the read mode.
• Issuing the IPB Instruction Set Exit will reset the device to normal read mode enabling reads
and writes for the array.
7.3.2.2 Dynamic Protection Bits (DPB)
Dynamic Protection allows the software applications to easily protect sectors against unintentional
changes, although, the protection can be readily disabled when changes are needed.
All Dynamic Protection Bits (DPB) are individually linked to their associated sectors and these volatile
bits can be modified individually (set or cleared). The DPB provide protection schemes for only
unprotected sectors that have their associated IPB cleared. To change a DPB, the “DPB Instruction
Set Entry” must be executed first and then either the DPB Set (programmed to “0”) or DPB Clear
(erased to “1”) commands have to be executed. This places each sector in the protected or
unprotected state separately. To exit the DPB mode, execute the “DPB Instruction Set Exit” instruction.
Note that
• When the parts are first shipped, the IPB are cleared (erased to “1”) and upon power up or
reset, the DPB can be set or cleared.
Publication Release Date: August 2, 2013
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Revision H