S75WS256NDFBAWMB datasheet(65/216 Pages) SPANSION

65 / 216 page

February 17, 2005 S75WS-N-00_A0

S75WS256Nxx Based MCPs

Advance

Information

11.2

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 pro-

gramming the Customer Secured Silicon Sector, but reading in Banks 1 through 15 is avail-

able.

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 mem-

ory array at sector 0.

11.3

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 13.1 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.

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