W19B320ATB Datasheet, PDF (10/53 Pages) Winbond – 4M × 8/2M × 16 BITS 3V FLEXIBLE BANK FLASH MEMORY

W19B320AT/B
6.1.11 Write Protect (#WP)
The Write Protect function provides a hardware method to protect the certain boot sectors without
using V_ID. This function is one of two features provided by the #WP/ACC pin.
When the #WP/ACC pin is set at V_IL, the device disables program and erase functions in the two
outermost 8 Kbytes boot sectors independently of whether those sectors were protected or
unprotected using the method described in “Sector/Sector Block Protection and Unprotection.” The
two outermost 8 Kbytes boot sectors are the two sectors containing either the lowest addresses in a
bottom-boot-configured device or the highest addresses in a top-boot-configured device.
When the #WP/ACC pin is set at V_IH, the device reverts to the two outermost 8 Kbytes boot sectors
were last set either to be protected or unprotected. That is, sector Protection or Unprotection for these
two sectors depends on whether they were last protected or unprotected using the method described
in “Sector/Sector Block Protection and Unprotection”.
Please note that the #WP/ACC pin must not be left floating or unconnected; otherwise, the
inconsistent behavior of the device may occur.
6.1.12 Temporary Sector Unprotect
This feature allows temporary Unprotection of previously protected sectors to change data in-system.
When the #RESET pin is set to V_ID, the Sector Unprotect mode is activated. During this mode,
formerly protected sectors can be programmed or erased by selecting the sector addresses. What if
V_ID is removed from the #RESET pin, all the previously protected sectors are protected again.
6.1.13 Security Sector Flash Memory Region
The Security Sector feature provides an OTP memory region that enables permanent device
identification through an Electronic Serial Number (ESN). The Security Sector uses a Security Sector
Indicator Bit (DQ7) to indicate whether the Security Sector is locked or not when shipped from the
factory. The DQ7 is permanently set when it is in the factory and cannot be changed, which prevents
copying of a factory locked part. This ensures the security of the ESN when the product is shipped to
the field. This issue should be considered during system design. Winbond offers the device with the
Security Sector either factory locked or customer lockable. The factory-locked version is always
protected when shipped from the factory, and has the Security Sector Indicator Bit permanently set to
“1” The customer-lockable version is shipped with the Security Sector unprotected, which allowing
customers to utilize the sector in any ways they choose. The customer-lockable version has the
Security Sector Indicator Bit permanently set to “0.” Thus, the Security Sector Indicator Bit prevents
customer-lockable devices from being used to replace devices that are factory locked.
The system accesses the Security Sector through a command sequence (see “Enter Security
Sector/Exit Security Sector Command Sequence”). After the system has written the Enter Security
Sector command sequence, it may read the Security Sector by using the addresses normally
occupied by the boot sectors. This mode of operation continues until the system issues the Exit
Security Sector command sequence, or until power is removed from the device. On power-up, or
following a hardware reset, the device reverts to sending commands to the boot sectors.
Factory Locked: Security Sector Programmed and Protected At the Factory
The device Security Sector is protected when it is shipped from the factory, and it cannot be modified
in any way. The device is available to be preprogrammed by one of the following:
• A random, secure ESN only
• Customer code through the supplier's service
• Both a random, secure ESN and customer code through supplier's service.
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