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AR# 43719

Spartan-3AN: Write protection becomes inactive after a new power cycle.


I have downloaded a Micro Controller System (MCS) file with write protection into the ISF of a Spartan3AN FPGA through iMPACT.

However I can still access and modify the content in ISF with SPI_ACCESS.

Will write protection become inactive after a new power cycle?


At power-up, the sector protection feature is disabled, meaning that the FPGA application has full program and erase access to all sectors.

If the application employs the sector protection feature, then the FPGA application should issue the "Sector Protection Enable " command immediately after the FPGA is configured.
The Sector Protection Enable command is issued by doing the following:
1. Drive CSB low while the CLK is high or on the rising edge of the CLK.
2. On the falling edge of the CLK, serially clock in the four-byte Sector Protection Enable command sequence "3D 2A 7F A9" on the MOSI pin, most-significant bit of each byte first.
3. After clocking in the last bit of the command sequence, drive the CSB pin High on the falling edge of the CLK.

The defined sector protection becomes active.
AR# 43719
Date Created 08/18/2011
Last Updated 08/28/2014
Status Active
Type General Article
  • Spartan-3AN