S29WS-NL Datasheet, PDF (63/99 Pages) SPANSION – 256/128/64 MEGABIT CMOS 1.8 VOLT ONLY SIMULTANEOUS READ/WRITE BURST MODE FLASH MEMORY

Advance Information
10.2
Customer Secured Silicon Sector
The Customer Secured Silicon Sector is typically shipped unprotected (DQ6 set to “0”), allowing
customers to utilize that sector in any manner they choose. If the security feature is not required,
the Customer Secured Silicon Sector can be treated as an additional Flash memory space.
Please note the following:
„ Once the Customer Secured Silicon Sector area is protected, the Customer Indicator Bit
is permanently set to “1.”
„ The Customer Secured Silicon Sector can be read any number of times, but can be pro-
grammed and locked only once. The Customer Secured Silicon Sector lock must be used
with caution as once locked, there is no procedure available for unlocking the Customer
Secured Silicon Sector area and none of the bits in the Customer Secured Silicon Sector
memory space can be modified in any way.
„ The accelerated programming (ACC) and unlock bypass functions are not available when
programming the Customer Secured Silicon Sector, but reading in Banks 1 through 15 is
available.
„ Once the Customer Secured Silicon Sector is locked and verified, the system must write
the Exit Secured Silicon Sector Region command sequence which return the device to the
memory array at sector 0.
10.3
Secured Silicon Sector Entry and Secured Silicon Sector
Exit Command Sequences
The system can access the Secured Silicon Sector region by issuing the three-cycle Enter Secured
Silicon Sector command sequence. The device continues to access the Secured Silicon Sector re-
gion until the system issues the four-cycle Exit Secured Silicon Sector command sequence.
See Command Definition Table [Secured Silicon Sector Command Table, Appendix
Table 12.1 for address and data requirements for both command sequences.
The Secured Silicon Sector Entry Command allows the following commands to be executed
„ Read customer and factory Secured Silicon areas
„ Program the customer Secured Silicon Sector
After the system has written the Enter Secured Silicon Sector command sequence, it may read
the Secured Silicon Sector by using the addresses normally occupied by sector SA0 within the
memory array. This mode of operation continues until the system issues the Exit Secured Silicon
Sector command sequence, or until power is removed from the device.
Software Functions and Sample Code
The following are C functions and source code examples of using the Secured Silicon Sector
Entry, Program, and exit commands. Refer to the Spansion Low Level Driver User’s Guide
(available soon on www.amd.com and www.fujitsu.com) for general information on Spansion
Flash memory software development guidelines.
Table 10.2. Secured Silicon Sector Entry
(LLD Function = lld_SecSiSectorEntryCmd)
Cycle
Operation
Byte Address
Word Address
Unlock Cycle 1
Write
Base + AAAh
Base + 555h
Unlock Cycle 2
Write
Base + 554h
Base + 2AAh
Entry Cycle
Note: Base = Base Address.
Write
Base + AAAh
Base + 555h
Data
00AAh
0055h
0088h
January 25, 2005 S29WS-N_00_G0
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