W29GL128CH9C-TR Datasheet, PDF (26/67 Pages) Winbond – 128M-BIT 3.0-VOLT PARALLEL FLASH MEMORY WITH PAGE MODE

W29GL128C
7.4 Security Sector Flash Memory Region
An extra memory space length of 128 words is used as the Security Sector Region which can be
factory locked or customer lockable. To enquire about the lock status of the device, the customer can
issue a Security Sector Protect Verify or Security Sector Factory Protect Verify using Automatic Select
Address 03h and DQ7.
The security sector region is unprotected when shipped from factory and the security silicon indicator
bit (DQ7) is set to "0" for a customer lockable device. The security sector region is protected when
shipped from factory and the security silicon sector indicator bit is set to "1" for a factory-locked device.
7.4.1 Factory Locked: Security Sector Programmed and Protected at factory
In a factory locked device, the Security Sector is permanently locked prior to factory shipment The
ESN occupies addresses 00000h to 0000Fh in byte mode or 00000h to 00007h in word mode since
the device has a 16-byte (8-word) ESN(Electronic Serial Number) in the security region.
Security Silicon
Sector Address
Range
Standard Factory
Locked
Express Flash
Factory Locked
000000h-000007h ESN
ESN or Determined by
Customer
000008h-00007Fh Inaccessible
Determined by
Customer
Table 7-12 Factory Locked: Security Sector
Customer Lockable
Determined by
Customer
7.4.2 Customer Lockable: Security Sector Not Programmed or Protected
Important Notice; Once the security silicon sector is protected (Lock Register OTP DQ0 = “0”, Security
Sector indicator DQ7 bit=”0”), there is no way to unprotect the security silicon sector and the contents
of the memory region can no longer be programmed.
Once the security silicon is locked and verified, an Exit Security Sector Region instruction must be
executed to get back to the Read Array mode. A power cycle, or a hardware reset will also return the
device to read array mode.
This region can act as extra memory space when this security feature is not utilized. It is important to
note, the security sector region is a One Time Programmable (OTP) region. You can overwrite a
WORD, but you cannot change the state of a programmed cell.
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