s29ns01gs Meet Spansion Inc., s29ns01gs Datasheet - Page 47

• Manufacturer Part Number: s29ns01gs
• Description: S29ns01gs 1024 Megabit 128 Megabyte 16-bit Data Width, Burst Access, Simultaneous Read/write, 1.8 Volt-only Flash Memory In 65 Nm Mirrorbit Technology
• Manufacturer: Meet Spansion Inc.

8.
8.1
April 20, 2009 S29NS-S_00_02
8.1.1
Data Protection
Secure Silicon Region
Factory Secure Silicon Region
The fundamental job of a non-volatile memory is to preserve the information (data) stored in the memory
array. In particular, to preserve the information during long periods when no power is applied to the memory.
The original non-volatile memory type was Read Only Memory (ROM) which preserved information
permanently by hard-wired connections of the memory array transistors. ROM provides great permanent data
storage but, no ability to make any changes to the data that might be desired at a later time.
Non-volatile memories evolved to add various methods for modifying data when needed. Flash memory has
become the most commonly used form of non-volatile memory because of its high density, high speed, and
electrical re-programmability that allows data to be easily updated within the host system.
However, the ability to easily change the stored data can be a problem if the data can be unintentionally
changed by power or signal anomalies (glitches), incorrect code execution, or even maliciously changed by
intentionally destructive code.
Data Protection features are provided in the Eclipse Flash family to either permanently or temporarily disable
programming or erase operations in selected portions of the memory. These data protection features enable
multiple levels of control over when data can be changed. This allows a more flexible balance between the
goal of preserving data and the ability to modify the data when desired.
This section describes the various methods of protecting data stored in the memory array. Some protection
features are implemented through hardware methods and some are under the control of software. They are
discussed in the order of protection precedence (highest to lowest priority).
The general principle used is that, in normal operation, data should be protected by default:
The Secure Silicon Region (SSR) provides an extra Flash memory region that may be programmed once and
permanently protected from further programming or erase. The SSR is made visible via an Address Space
Overlay (ASO) command. The protection of SSR is controlled by the SSR Lock ASO.
The Factory Secure Silicon Region is always protected when shipped from the factory and has the Factory
SSR Lock Bit (bit 1) permanently set to a Zero. This prevents cloning of a factory locked part and ensures the
security of the ESN and customer code once the product is shipped to the field.
Data in each Flash memory array sector is protected unless protection is explicitly removed
Some sectors can be configured to not allow protection to be removed
For those sectors where protection is allowed to be removed, protection can only be removed from one
sector at a time
Once protection is removed from a sector, multiple program and erase operations may be performed in the
sector, until protection is restored for that sector
Reads can be performed in the Asynchronous or Synchronous mode.
Sector address supplied during the Secure Silicon Entry command selects the Flash memory array sector
that is overlaid by the Secure Silicon Region address map.
Continuous burst mode reads within Secure Silicon Region wrap from byte address 3FFh back to address
000h.
Reads outside of the overlaid sector return memory array data.
The Secure Silicon Region can't be entered when the device is executing an Embedded Algorithm (nor
during Program Suspend, Erase Suspend, or while another AOS is active).
See the Secure Silicon address map for address range of this area.
Both Write-Buffer and Bit-Field programming may be used in the SSR.
D a t a
S h e e t
S29NS-S MirrorBit
( P r e l i m i n a r y )
®
Eclipse
™
Flash Family
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