Document Number: 002-00833 Rev. *L
Page 41 of 74
S29VS256R
S29VS128R
S29XS256R
S29XS128R
8.5.2
Customer Secure Silicon Region
The Customer Secure Silicon Region is typically shipped unprotected, Customer SSR Lock Bit (bit 0) set to a one, allowing
customers to utilize that sector in any manner they choose.
The Customer Secure Silicon Region can be read any number of times, but each word CL can be programmed only once and the
region locked only once. The Customer Secure Silicon Region lock must be used with caution as once locked, there is no procedure
available for unlocking the Customer Secure Silicon Region area and none of the bits in the Customer Secure Silicon Region
memory space can be modified in any way. The Customer Indicator Bit is located in the SSR Lock at bit location 0.
Once the Customer Secure Silicon Region area is protected, any further attempts to program in the area will fail with status
indicating the area being programmed is protected.
8.5.3
Secure Silicon Region Entry and Exit Command Sequences
The system can access the Secure Silicon Region region by issuing the one-cycle Enter Secure Silicon Region Entry command
sequence from the IDLE State. The device continues to have access to the Secure Silicon Region region until the system issues the
Exit Secure Silicon Region command sequence, performs a Hardware RESET, or until power is removed from the device.
See Command Definition Table [Secure Silicon Region Command Table, Appendix
for address and data requirements for both command sequences.
The Secure Silicon Region Entry Command allows the following commands to be executed
Read customer and factory Secure Silicon Regions
Program the customer Secure Silicon Region
Read data out of all sectors not re-mapped to Secure Silicon Region
Secure Silicon Region Exit
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
Cypress Low Level Driver User’s Guide
(available on
) for general information on Cypress Flash
memory software development guidelines.
/* Example: SecSi Sector Entry Command */
*( (UINT16 *)sector_a 0x555 ) = 0x0088; /* write Secsi Sector Entry Cmd */
/* Once in the SecSi Sector mode, you program */
/* words using the programming algorithm. */
Table 38. Secured Silicon Region Entry
Cycle
Operation
Byte Address
Word Address
Data
Entry Cycle
Write
Sector A AAAh
Sector A 555h
0088h
Table 39. Secured Silicon Region Program
Cycle
Operation
Byte Address
Word Address
Data
Program Setup
Write
Sector A AAAh
Sector A 555h
0025h
Write Word Count
Write
Sector A 555h
Sector A 2AA
Word Count (N–1)h
Number of words (N) loaded into the write buffer can be from 1 to 32 words.
Load Buffer Word N
Write
Program Address, Word N
Word N
Write Buffer to Flash
Write
Sector A AAAh
Sector A 555h
0029h
